A High-Performance 10mm Diameter MEMS Fast Steering Mirror with Integrated Piezoresistive Angle Sensors for Laser Inter-Satellite Links

A High-Performance 10mm Diameter MEMS Fast Steering Mirror with Integrated Piezoresistive Angle Sensors for Laser Inter-Satellite Links | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article A High-Performance 10mm Diameter MEMS Fast Steering Mirror with Integrated Piezoresistive Angle Sensors for Laser Inter-Satellite Links Zhenyu Wu, Wenli Xue, Yichen Liu, Xingwang Zhu, Mingkun Wang, and 7 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5616577/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 29 Apr, 2025 Read the published version in Microsystems & Nanoengineering → Version 1 posted 10 You are reading this latest preprint version Abstract This paper presents a compact and high-performance piezoelectric Micro-Electro-Mechanical System (MEMS) Fast Steering Mirror (FSM) designed for use in laser Inter-Satellite Links (ISLs). The FSM features a large optical aperture of 10 mm and is batch fabricated using an 8-inch wafer-level eutectic bonding process, packaged into a volume of 26 × 22 × 3 mm 3 . Notably, the piezoresistive (PZR) sensor is integrated on the spring of the FSM to facilitate precise beam control. Furthermore, an intermediate directional defect structure is novelly designed to create a Stress Concentration Region (SCR), effectively improving PZR sensitivity from 3.3 mV/(V·mrad) to 5.4 mV/(V·mrad). In this article, various performance metrics of the FSM are tested, including the mechanical characteristics, PZR sensor properties, and mirror optical quality, which all meet the requirements for laser ISLs. Results indicate that the FSM achieves a high resonant frequency (>1 kHz) and a low nonlinearity of 0.05%@±2.1 mrad. A remarkable minimum angular resolution of 0.3 μrad and a repeated positioning accuracy of 1.11 μrad ensure exceptional pointing precision. The open-loop control is driven by the double-step algorithm, resulting in a step response time of 0.41 ms and achieving a control bandwidth over 2 kHz. Additionally, the integrated angular sensor demonstrates a nonlinearity of 0.09%@±1.05 mrad, a sensitivity of 5.1 mV/(V·mrad), and a minimum angular resolution of 0.3 μrad. Under quasi-static driven conditions (500 Hz @±2 mrad), the maximum dynamic deformation of the mirror surface is merely 2 nm. MEMS FSM Piezoresistive Sensor Laser Inter-satellite Link Quasi-Static Dynamic Deformation Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1 INTRODUCTION In recent years, the development of Inter-Satellite Links (ISLs) has attracted significant attention due to the increasing demands for space communication. ISLs enable high-speed data transfer between satellites, greatly enhancing the overall performance and flexibility of satellite networks 1 . Laser communication technology is recognized as a key enabler for efficient ISLs, offering advantages such as higher communication capacity, wider spectrum bandwidth, lower power consumption, and enhanced resilience to interference compared with Radio Frequency (RF) communication 2 . Currently, networks such as Starlink, SLILEX, LCTSX, G60, and China SatNet have already adopted laser ISLs as one of their core transmission methodologies. Laser communication terminals are anticipated to become standard communication equipment in future spacecraft payloads. However, achieving extremely precise beam pointing poses a significant challenge in the implementation of ISLs. The Pointing, Acquisition, and Tracking (PAT) system is a core module for optical communications between satellites and between satellite and Earth 3 , 4 . A Fast Steering Mirror (FSM) with high precision and optical quality is essential to the PAT system, functioning as the core device for achieving accurate beam steering in current state-of-the-art solutions 5 . Traditional FSMs are typically actuated using voice coil motors or piezoelectric ceramics. Voice coil motor-based FSMs generate driving force using magnetic fields, providing significant stroke lengths, low driving voltages, and high load capacities that enhance reliability. However, these systems need improved magnetic shielding and have limited operational frequencies, which may affect their robustness 6 . Piezoelectric ceramic FSMs leverage the inverse piezoelectric effect of bulk piezoelectric materials, such as PZT, to generate a driving force. While they offer strong driving force and quick response times, PZT faces challenges with impact resistance and reliability. Additionally, PZT's hysteresis requires complex driving circuits and compensation algorithms. The larger size and weight of traditional fast steering mirrors render them unsuitable for compact satellite platforms, complicating miniaturization efforts and increasing launch costs, thereby limiting mass production potential in commercial applications 7 . Recently, an increasing number of research institutions have begun utilizing commercial off-the-shelf (COTS) MEMS FSMs to construct their systems. Due to their low cost, small size, lightweight, and low power consumption, the MEMS FSMs hold significant application potential in laser ISLs. For example, many institutions use an electrostatic comb-drive MEMS FSM from Mirrorcle Technologies. The CubeSat Laser Infrared CrosslinK (CLICK) mission is a technology demonstration for CubeSat optical communication terminals, focusing on downlinks and crosslinks 8 , 9 . The CLICK-A 1.2U downlink terminal employs a 5 mm MEMS FSM. The results showed that the MEMS FSM was able to correct an average blind spacecraft pointing of 8.494 mrad and maintain an average RMS pointing error of 0.175 mrad after initial blind pointing error correction. Another CubeSat laser downlink demonstration mission, developed at the MIT Space Telecommunications, Astronomy, and Radiation Laboratory 10 , used a 3.6 mm MEMS FSM. Experimental results showed that beacon tracking errors of only 16 µrad RMS are feasible for both axes. The satellites team of the Stanford Student Space Initiative (SSI) designed and built the Polar-Orbiting Infrared Tracking Receiver (POINTR), a 1U CubeSat payload aimed to demonstrate optical-communications technology. A 4.2 mm gold-plated MEMS FSM was used on their 1U terminal and received a 0.5° tracking FOV 11 . The Aerospace Corporation (El Segundo, USA) let their design fit within 1U with a 6.4 mm diameter MEMS FSM which enables minimization of SWaP in the laser communication terminal, which is crucial in CubeSat laser communications. The prototype was designed such that it has an acquisition FOV of 2° and tracking FOV of 0.5°, with an acquisition time measured at less than 60 seconds and a success probability exceeding 99% 5 . These four institutions mentioned above all used COTS MEMS FSMs from Mirrorcle Technologies. Besides these, an electromagnetically driven 3 mm Hamamatsu S1227-03P MEMS FSM was used by the Laboratory of Lean Satellite Enterprises and In-Orbit Experiments (LaSEINE) in Japan to stabilize a laser communication link on an optical bench in the laboratory. In the closed-loop mode, they used a photodiode array PDA sensor to receive stabilization for over 20 seconds despite the induced fluctuations by the vibration machine 12 . Furthermore, closed-loop control can provide more stable and precise beam control, thereby improving system tracking accuracy. However, existing COTS MEMS FSMs generally lack integrated sensors and some research institutions rely on external sensors, such as the beacon detector 10 , consisting of a focal plane array (FPA) and a focusing lens assembly (LA), and the PDA sensor 12 , to construct closed-loop control systems. These approaches not only increase the overall size of the system but also lead to higher costs. Consequently, current COTS MEMS FSMs are not designed for the specific requirements of laser ISLs, exhibiting several shortcomings such as small mirror sizes, low frequency, and the lack of integrated sensors. To meet the requirements of laser ISLs, the key criteria of an FSM include 13 :(1) Size, Weight, and Power (SWaP): SWaP is the critical constraint for compact satellite platforms. The mass of FSMs typically ranges from a few grams to several kilograms, depending on the technology used and the dimensions of the mirror. Minimizing component size contributes to a more compact laser terminal, facilitating miniaturization and reducing satellite launch costs; (2) Optical/Mechanical Steering Angles: The mechanical steering angle of the mirror refers to its angular deviation from a reference position. A larger steering angle provides significant advantages for both the transmitter and receiver by expanding the field of view (FOV) necessary for effective tracking. The mechanical angle requirements for FSM in laser ISLs need to achieve at least ± 1.5 mrad; (3) Operational Bandwidth: The operational bandwidth of the FSM indicates its responsiveness to control signals and its capacity for rapid positional adjustments. For instance, the bandwidth criteria for FSM are closely linked to satellite oscillations 14 . Typically, the required bandwidths for an FSM range from several hundred Hz to over 1kHz; (4) Pointing Accuracy: Pointing accuracy is an important measure that depends on the resolution and repeatability of an FSM, which is vital for long-distance laser ISLs. Additionally, an angle sensor can provide real-time monitoring of mirror deflection angles, enabling more precise beam control through closed-loop systems. The current state-of-the-art fine beam pointing systems have pointing accuracies ranging from ± 48 µrad to ± 0.48 µrad 15 , 16 ; (5) Mirror Surface Quality: The quality of the mirror surface, characterized by measures such as root mean square (RMS) and peak-to-valley (PV) displacements, must be minimized to ensure optimal performance. For laser ISLs, the requirement is RMS < λ/20 at λ = 1550 nm. This study focuses on the development of a high-performance, compact MEMS FSM with a diameter of 10 mm, specifically designed for laser ISLs. It integrates an on-chip, high-sensitivity piezoresistive (PZR) sensor elements to achieve more precise beam control. The structure of this paper is as follows: Section 2 provides the design and simulation results of the mechanical structure. It also discusses the design principles of the PZR structure and optimization strategies for sensitivity. Section 3 details the fabrication process for the MEMS FSM. Section 4 presents the characterization results of the MEMS FSM, including mechanical performance, repeatability accuracy, control bandwidth, piezoresistive performance, and the dynamic deformation of the mirror surface. Additionally, at the end of this section, we perform a comparative analysis between various FSMs and the device presented in this study. Ultimately, in Section 5 , the research findings are summarized, and potential directions for future optimization are suggested. 2 Design Concept This study aims to develop a high-performance MEMS FSM specifically designed for laser ISLs. By optimizing the mechanical structure, this design achieves a high resonant frequency, meeting the requirement for laser ISLs above 1 kHz. In addition, while maintaining a mirror plate of 10 mm, the chip size has been significantly reduced 17 , increasing the fill factor. This makes the device particularly well-suited for compact satellite platforms and leads to a reduction in launch costs, making it an economically viable option for space applications. In addition, an innovative stress concentration structure is designed to improve the sensitivity of the integrated PZR sensors, enabling more precise beam control. 2.1 Design of the device structure To achieve a higher fill factor and resonant frequency, this design uses a double-layered stacked structure similar to that described in our previous work 17 , 18 . The MEMS FSM consists of two parts: the actuator and the mirror. The actuator layer consists of a frame, cantilevers, springs, and a support pillar. Two pairs of cantilevers are connected to the support pillar via springs. Additionally, the support pillar is joined to the center of the 10 mm mirror plate through a wafer-level bonding process, which facilitates precise alignment and enhances structural reliability. Notably, this structure magnifies the deflecting angle of the mirror by the leverage principle. Piezoelectric thin films are compatible with semiconductor processes, and we choose Sc-doped AlN (AlScN) film as the driving material. Although PZT has a higher piezoelectric coefficient, its hysteresis property brings a nonlinearity problem, and prolonged exposure to an electric field can lead to fatigue, adversely affecting the long-term stability of devices. The AlN film has high linearity and high reliability, but the piezoelectric coefficient is too low to satisfy the requirement of large deformation under the quasi-static operation of FSM. Therefore, in this work, AlScN film is used as the driving material, which has a higher piezoelectric coefficient along with the advantages of AlN. The AlScN film we use is doped with 20% of Sc element 19 . The optimization of the spring structure, in conjunction with finite element analysis (FEA) simulations, has led to an increased resonant frequency and a significant reduction in chip size which meet the requirement for the laser ISLs. Figure 1 a shows the simulation structure of the MEMS FSM with a 10 mm circular optical aperture. The fixed support point is the anchor point of the cantilever beam that connects to the frame. Figure 1 b-d show the FEA simulation results for the first three vibrational modes. The first mode is the tip/tilt mode of two axes with a frequency of 1253 Hz. The third mode of the MEMS FSM is the piston mode at 2827 Hz, which is increased to higher than 2 kHz. This enhancement effectively minimizes the susceptibility to critical resonant frequencies in the ambient random vibrations ranging from 20 to 2000 Hz, thereby improving the device's reliability under such conditions 20 . Furthermore, simulations of the tilting angle indicate that the maximum tilting angle of the mirror reaches 2 mrad at an applied voltage of 90 V. 2.2 Design of the piezoresistive sensor As shown in Fig. 1 e, the PZR sensor is a Wheatstone bridge consisting of four piezoresistive bars which are strategically positioned on the spring of the FSM. When the FSM tilts, the spring connecting the cantilever beam and the pillar experiences considerable normal stress. This stress induces deformation within the piezoresistive elements, leading to a change in their resistivity, which subsequently alters the output voltage of the bridge circuit. The normal stress at the piezoresistive position is directly proportional to the FSM's tilting angle. Consequently, this relationship allows for real-time monitoring of the FSM's position through variations in the output voltage of the Wheatstone bridge. The FSM employs P-type PZRs and the maximum output voltage of the PZRs can be achieved when both the cantilever beam and PZRs are oriented along the crystal direction. The formula for calculating the bridge output voltage is provided in the following expression: $$\:{V}_{output}=\left(\frac{R3}{R2+R3}-\frac{R4}{R1+R4}\right){V}_{input}=\left(\frac{1+\frac{\varDelta\:R3}{R3}}{2+\frac{\varDelta\:R2}{R2}+\frac{\varDelta\:R3}{R3}}-\frac{1+\frac{\varDelta\:R4}{R4}}{2+\frac{\varDelta\:R1}{R1}+\frac{\varDelta\:R4}{R4}}\right){V}_{input}$$ 1 \(\:{V}_{input}\) is the supply voltage, \(\:\frac{\varDelta\:R}{R}\) is the change in resistance of the PZRs at each position, expressed as: $$\:\frac{\varDelta\:R}{R}={\pi\:}_{l,110}{\sigma\:}_{l}+{\pi\:}_{t,110}{\sigma\:}_{t}$$ 2 \(\:{\pi\:}_{l,110}\) and \(\:{\pi\:}_{t,110}\) are the longitudinal and transverse piezoresistive coefficients of the PZRs oriented along the crystal direction. \(\:{\sigma\:}_{l}\) and \(\:{\sigma\:}_{t}\) are the longitudinal and transverse stresses acting on the PZR position. For P-type PZRs with a doping concentration of 1e19 cm − 3 , \(\:{\pi\:}_{l,110}=43\times\:{10}^{-11}{\text{P}\text{a}}^{-1}\) and \(\:{\pi\:}_{t,110}=-40\times\:{10}^{-11}{\text{P}\text{a}}^{-1}\) 2 1 。 High-sensitivity piezoresistive sensors can yield greater voltage output under the same micro-mirror rotation angle, enhancing the angular resolution of the PZRs and enabling more precise beam control. The expression for PZR sensor sensitivity is given as: $$\:S=\frac{{V}_{output}}{{V}_{input}*{\theta\:}_{mech}}$$ 3 \(\:{\theta\:}_{mech}\) is the mechanical steering angle of the FSM. To enhance the sensitivity of the PZRs while maintaining the same supply voltage and doping concentration, it is essential to increase the stress experienced at the PZR position when the FSM tilts. In this study, a novel intermediate directional defect structure is designed at the front end of the cantilever beam. Figure 1 f depicts a micrograph of the PZR position. Four long and narrow slots are etched to create a stress concentration region (SCR). Here, we give three different structures at the PZR position. Figure 1 g presents the stress simulation results at the PZR position under a tilting angle of the FSM at 2 mrad. Design1 represents the baseline structure without SCR, with only relatively high stress appearing at the narrow spring position of R3. Design2 has two etched slots, concentrating stress at the position of R2 in addition to the position of R3. As shown in the figure, the stress distribution at the position of R2 appears smaller in the middle and larger on the sides. Following further optimization, Design3 introduces four slots, whose orientations are pointed to the middle, concentrating stress entirely at the position of the central PZR (R2), maximizing the PZR sensitivity. Table 1 provides the transverse and longitudinal stress magnitudes at the PZR position for the three designs, along with the calculated PZR sensitivity, showing a 63% improvement for Design3 compared to the initial design. Theoretically, the piezoresistive sensitivity of Design3 is 5.4 mV/(V \(\:\bullet\:\) mrad). Table 1 Piezoresistive sensitivity comparison of three designs Design1 Design2 Design3 \(\:{\sigma\:}_{l}\) (Mpa) \(\:{\sigma\:}_{t}\) (Mpa) \(\:{\sigma\:}_{l}\) (Mpa) \(\:{\sigma\:}_{t}\) (Mpa) \(\:{\sigma\:}_{l}\) (Mpa) \(\:{\sigma\:}_{t}\) (Mpa) R1 8 -6 27 3 49 -4 R2 -5 3 -5 6 -6 3 R3 29 -4 28 5 26 -6 R4 -5 3 -5 6 -6 3 Sensitivity (mV/(V \(\:\bullet\:\) mrad)) 3.3 3.6 5.4 3 Fabrication The PZR-integrated MEMS FSM utilizes an SSD (SOI based Single piezoelectric layer Double release)-FSM process consisting of two layers: an AlScN actuator wafer and a mirror plate wafer. The AlScN actuator wafer starts with an SOI wafer with a 500 µm handle layer, a 1 µm buried oxide layer, and a 100 µm device layer. The mirror plate wafer needs an SOI wafer with a 450 µm handle layer, a 1 µm buried oxide layer, and a 50 µm device layer. The process used for its fabrication, which is suitable for 8-inch mass production, is depicted in Fig. 2 a. The fabrication process of the actuator layer is divided into five main steps: (1) Firstly, a 50 nm thick silicon oxide layer is thermally oxygenated on the surface. Then, the p-type piezoresistive sensors are formed by phosphorus ion injection and thermally annealed, and the doping concentration of the piezoresistive sensors is \(\:\text{1×}{\text{10}}^{\text{19}}\text{/}{\text{cm}}^{\text{3}}\) . However, due to the relatively low doping concentration of boron ions, further phosphorus ion implantation is required for better subsequent ohmic contacts. (2) The upper electrode Mo (200 nm), the piezoelectric layer AlScN (1.5 µm), and the lower electrode Mo (200 nm) were deposited on top of the oxide layer by magnetron sputtering and patterned. (3) On the top Mo layer, 500 nm silicon oxide is deposited by the PECVD (plasma enhanced chemical vapor deposition) process as a passivation layer and then dry-etched by RIE (Reactive Ion Etching) to form the electrical contact via. After that, a 1 µm Al layer is deposited by magnetron sputtering on the wafer and patterned to form electrical connections. (4) The 100 µm device layer is patterned by DRIE (Deep Reactive Ion Etching) to form the actuators and springs. Then, a 500nm Al layer is deposited by magnetron sputtering on the backside of the handle layer as a bonding metal. (5) The bonding metal and the handle layer are patterned and etched by DRIE from the back side to release all the movable parts of the device. The fabrication process of the mirror layer is divided into three main steps: (6) A 500 nm Ge layer is sputtered on the bottom silicon as the bonding layer. (7) The Ge layer is patterned for next eutectic bonding. (8) A honeycomb-shaped reinforcement structure was patterned and etched into the bottom silicon by DRIE to reduce the mass and strengthen the stiffness of the mirror plate. (9) Bond the mirror plate wafer to the actuator wafer and release the mirror. Finally, Au is magnetron sputtered as the mirror reflective layer. Figure 2 b gives the photograph of the packaged MEMS FSM and Fig. 2 c summarizes the final parameters of the MEMS FSM. 4 Results and discussion After completing the fabrication of the device, we characterize the basic mechanical properties (including resonance frequency, mechanical tilting angle, nonlinearity, and angular resolution), pointing accuracy, open-loop control performance (including step response, operational bandwidth, and stability), PZR performance (including sensitivity, nonlinearity, stability, and angular resolution) and the dynamic deformation of the mirror. 4.1 Performance test platform Figure 3 a, b gives the Position Sensitive Detectors (PSD) test schematic and the built test platform. The laser emitted by the laser source is reflected by the mirror plate and received by the PSD, which records the position of the laser spot. When the driving signal generated by the computer acts on the MEMS FSM through the data acquisition card, the mirror will tilt, resulting in a change in the position of the laser spot. This positional change is then calculated to determine the tilting angle of the MEMS FSM and recorded by the computer. The PSD exhibits a rapid response speed and enhanced temporal resolution, resulting in superior performance in tests that require quick and sensitive dynamic responses. However, PSD is sensitive to variations in ambient light and temperature, resulting in high levels of noise (> 10 µrad). To achieve a more accurate characterization of the angular resolution of the FSM and pointing accuracy, a collimator test system shown in Fig. 3 c, d is constructed. The collimator directs a collimated beam of light towards the mirror. As the mirror is actuated and deflecting, it alters the direction of the reflected beam. A detection system analyzes the deviation of the reflected beam. By calculating the change in beam position relative to the initial alignment, the tilting angle of the FSM can be accurately determined and recorded by the computer. 4.2 The basic mechanical performance Initially, we characterize the basic mechanical performance of the FSM. As shown in Fig. 4 a, the frequency response is assessed using Laser Doppler Velocimetry (LDV), revealing resonant frequencies of 1231.2 Hz for the x-axis and 1228.1 Hz for the y-axis, which are consistent with the simulation results. To evaluate the mechanical tilting angle and nonlinearity of the FSM, a sequence of direct current (DC) voltages ranging from − 110 V to + 110 V, with an increment of 11 V each step, is applied. Figure 4 b shows that the nonlinearities of the x-axis and y-axis measure 0.04%@±2.16 mrad and 0.05%@±2.18 mrad, which is the full-scale, the maximum driving voltage that our piezoelectric film can withstand, of the device. The nonlinearity of both axes is smaller than 0.1%, ensuring the pointing accuracy for the FSM. Additionally, the angular resolution of the FSM is tested, which is also a critical parameter for pointing accuracy. Figure 4 c, d shows the angular resolution results obtained using the collimator testing system. A step wave is used for driving, wherein each voltage was held for 0.5 seconds while recording data at a rate of 100 points per second. It can be observed that the minimum angular resolution of the FSM, which can be tested under the current test platform, is 0.3 µrad @ 16.5 mV. However, at a lower driving voltage of 13.75 mV, likely due to either the noise inherent in the testing system or limitations associated with the device itself, a smaller angular resolution could not be obtained. Such high precision is critical for maintaining accurate pointing and tracking capabilities, which ensure effective communication in dynamic environments. 4.3 Pointing Accuracy In addition to nonlinearity and angular resolution, the repeatability of the FSM is another critical metric for assessing its pointing accuracy. In Fig. 4 e, a voltage of + 55V, + 27.5V, 0V, -27.5V, and − 55V is applied to both axes, randomly sampling positions in a 5 \(\:\times\:\) 5 grid and repeating this process 32 times. By zooming in on one point, it can be observed that: thirty-two points are randomly distributed over a small range, 1.5 µrad in the x direction and 2µrad in the y direction. To further quantify the repeatability of the FSM, the voltage is cycled from 0V to -55V, -44V, ..., 55V back and forth 32 times for each target voltage. Whenever returning to 0V, we record the tilting angle and the triple standard deviation (3σ) of the 32 measurements is calculated as shown in Fig. 4 f. The maximum value of 3σ at different voltages is defined as the zero-point repeatability, yielding values of 1.11 µrad for the x-axis and 1.05 µrad for the y-axis. Similarly, in Fig. 4 g, the voltage is cycled from 0V to -55V, -44V, ..., 55V back and forth 32 times for each target voltage. Whenever reaching the target voltage, we record the tilting angle, and the 3σ of 32 measurements is calculated. The maximum value of the 3σ at different voltages is defined as repeatable positioning accuracy, resulting in values of 1.09 µrad for the x-axis and 1.04 µrad for the y-axis. This analysis underscores the FSM's capability to achieve precise angular positioning. 4.4 Open loop control performance To measure the open-loop step response of the MEMS FSM, a step voltage is applied to drive the mirror. As depicted in Fig. 4 h, the maximum overshoots for both axes exceed 100%, and the settling time of the step response is long under open-loop control. Therefore, a double-step feedforward control algorithm is applied to the device and the step response performance of the device. The overshoot is sharply decreased and the settling time is only 0.41ms. Thus, an open loop operational bandwidth of more than 2000 Hz can be obtained through the feedforward control algorithm 22 . In Fig. 4 i the X-axis is actuated using the feedforward control algorithm. The red line in the figure represents the driving voltage, which is a step voltage that changes upon the mirror reaching the desired angle. Throughout the experiment, nine distinct target voltages were utilized: ±55 V, ± 41.25 V, ± 27.5 V, ± 13.75 V, and 0 V, with a control cycle of 0.48 ms. A control bandwidth of 2083 Hz is achieved. The high-frequency response of FSMs allows for real-time compensation of the oscillations experienced by satellites, ensuring that the laser beam remains accurately directed at the target. Figure 4 j characterizes the stability of the device by independently driving each axis through a sequence of voltages: -27.5 V, -55 V, -27.5 V, 0 V, 27.5 V, and 55 V, maintaining each voltage for one hour. Under a driving voltage of 55 V, the maximum fluctuation observed within this hour was 2.8 µrad for the X-axis and 3.1 µrad for the Y-axis. The high stability is critical for ensuring the accuracy of the overall system performance. 4.5 PZR sensor performance The integrated PZR sensors have the potential to enhance the mirror’s performance in laser ISLs by providing more precise beam control, real-time feedback, and the ability to compensate for external disturbances, ultimately leading to more reliable and efficient communication systems. Figure 5 presents the performance of the PZR sensors of the MEMS FSM. The PZR output signal is collected by a data acquisition card and recorded by computer. In Fig. 5 a, we obtain the relationship between the output voltage of the PZR sensor and the deflection angle. A sequence of DC voltages ranging from − 55 V to + 55 V, with increments of 11 V, are applied to the FSM. The supply voltage for the PZR sensor is set at 0.25 mV, and the output signal is amplified by a factor of 1000. The nonlinearity observed between the sensor signal and the deflection angles for the x-axis and y-axis is measured at 0.08% and 0.09%, respectively, based on the half-scale range of ± 55 V for the device. The sensitivity is calculated to be 5.036 mV/(V \(\:\bullet\:\) mrad) for the x-axis and 5.024 mV/(V \(\:\bullet\:\) mrad) for the y-axis, which shows favorable agreement with the simulation result and proves that the SCR can effectively improve the sensitivity. Figure 5 b characterizes the synchronism between the sensor output and the deflecting angle of the FSM. A stepped waveform voltage of 550 mV each step is given to actuate the mirror, while the deflection angle and the corresponding output signal from the PZR sensor are simultaneously recorded. The result shows a good synchronism between the voltage output of the sensor and the angle. Figure 5 c depicts the stability test of the PZR sensor, where both axes are individually driven through the following sequence of voltages: -27.5 V, -55 V, -27.5 V, 0 V, 27.5 V, 55 V, 27.5 V, and 0 V, with each voltage maintained for one hour. The recorded PZR output signals reveal that, after amplifying the resistive signal under a 55 V drive, the maximum fluctuations observed within this hour were 1.5 mV for the x-axis and 1.2 mV for the y-axis. Figure 5 d, e shows the results of the angular resolution test of the PZR sensor. To achieve a smaller angular resolution, the supply voltage and amplification factor are adjusted to minimize noise in the resistive output signal. As shown in Fig. 5 d, when the PZR supply voltage is 1.2 V and the PZR output voltage is amplified by a factor of 200, the minimum angular resolution of the resistive sensor is 0.3 µ [email protected] mV. Figure 5 e demonstrates that at a lower driving voltage of 11mV, the resistive sensor fails to respond adequately to every step change. 4.6 Dynamic deformation of the mirror plate The rapid motion of the MEMS fast steering mirror (FSM) results in dynamic deformation of the mirror surface, as shown in Fig. 6 a. This dynamic deformation, defined as the deviation from linearity, can be predicted using Brosens’s formula below, which uses the unevenly distributed forces due to acceleration across the mirror surface 23 . $$\:{\delta\:}_{max}=0.217\frac{\rho\:{f}^{2}{D}^{5}{\theta\:}_{mech}}{E{t}_{m}^{2}}$$ 4 where \(\:\rho\:\) is the material density, \(\:E\) is the modulus of elasticity, \(\:f\) is the scanner frequency, \(\:D\) is the mirror aperture, \(\:\:{\theta\:}_{mech}\) the mechanical tilting angle, and \(\:\:{t}_{m}\) is the mirror thickness. To keep the spot diffraction limited, the maximum mechanical mirror deformation ( \(\:{\:\delta\:}_{max}\:\) ) should not exceed \(\:\lambda\:/10\:\) of the shortest system wavelength 24 . To enhance resistance to static deformation, we optimized the rib shapes and sizes while maintaining the same mirror mass and ultimately, we selected a honeycomb-shaped reinforcement structure for the mirror 18 . Figure 6 d shows the static deformation of our mirror measured by a Fizeau interferometer (Zygo Verifire interferometer, America). The average PV value and RMS value of the surface figure of the devices are 87 nm and 12 nm. It is worth noting that the RMS value is merely λ/120 (λ = 1550 nm). In addition, the reinforcement structure of the mirror also contributes to reducing dynamic deformation. Figure 6 b, c shows the dynamic deformation simulation results for the dynamic deformation of the mirror subjected to a tilting angle of 2 mrad at a frequency of 500 Hz. The reinforced mirror exhibits a maximum dynamic deformation of 2.15 nm, whereas the equivalent mass pure mirror model demonstrates a significantly higher maximum dynamic deformation of 9.55 nm. This indicates that the reinforced structure effectively reduces dynamic deformation by a factor of four compared to the unreinforced model. a Schematic diagram of mirror dynamic deformation; b FEA simulation of dynamic deformation of equivalent mass mirror model (2 mrad@500 Hz); c FEA simulation of dynamic deformation reinforced mirror model (2 mrad@500 Hz); d Static deformation of the mirror tested by a Fizeau interferometer; e The experimental setup for dynamic deformation measurement; f Static deformation of the mirror tested by DHM; g Topography recorded by DHM; h Correcting for the tilting angle; i Subtracting static deformation, resulting dynamic deformation Currently, there is a limited amount of experimental research on dynamic deformation. Earlier studies measured dynamic deformation using LDV 25 , phase shifting interferometry 26 , and Shack Hartmann wavefront sensor (SHWS) 27 . These approaches rely on manual point measurements or offer poor lateral resolution, and they are primarily designed for dynamic deformation measurement of small mirrors (less than 2 mm in size). Recently, Silicon Austria Labs GmbH presented an approach using Digital Holographic Microscopy (DHM) 28 , which has high nanometric vertical resolution and compared to SHWS, much higher lateral resolution, to measure the dynamic deformation of a 2mm resonating piezoelectric MEMS mirror. In this paper, we also use the DHM R2100 from Lync ́ee Te, to measure the dynamic deformation of the MEMS FSM. The measurements are performed using an objective with a magnification of 2.5x, an NA of 0.07, and a field of view of 2.64 mm. As our 10 mm mirror plate is far beyond the field of view, a stitching mode is needed to measure such a big mirror. Figure 6 f is the topography of the mirror stitched by DHM at a static state. The surface topography of the FSM is basically the same as that measured by the Fizeau interferometer. According to the simulation result, under a quasi-static state (2 mrad@500 Hz), the dynamic deformation is only 2.15 nm and the surface topography of the mirror remains largely consistent with its static state. The dynamic deformation will be submerged in its own static deformation and system test noise. Therefore, we choose to measure the frequency near the resonance region while the mirror tilts at larger angles, where the mirror produces a more pronounced dynamic deformation. According to the simulation result, the maximum dynamic deformation of the mirror of 35 mrad (2°) @1108 Hz is 181 nm. This value exceeds that of the static deformation and the system noise and can be measured by DHM. However, the vertical height of the mirror is higher than 300 µm, which is larger than the maximum measurable vertical height attainable by DHM. Therefore, a goniometer is needed 28 , as shown in Fig. 6 e, to manually adjust the angle of the micromirror so that the FSM is exactly perpendicular to the objective lens at 2° so that the vertical height difference across the mirror is within holographically measurable limits. Figure 6 g shows the deformation map of the mirror at 1108 Hz. The mirror has a slight angle (4 mrad) relative to the objective plane. As shown in Fig. 6 h, a plane is fitted to the deformation map and this residual tilt angle is added to the set angle of the goniometer to obtain a final tilt angle of 31 mrad. Figure 6 i gives the max dynamic deformation of the mirror of 31 mrad at 1108 Hz is 130 nm, which is basically consistent with the simulation value 161 nm. We can infer that the dynamic deformation of our MEMS FSM is less than 2 nm in the quasi-static state by characterizing the dynamic deformation under a large angle around the resonant frequency. The low dynamic deformation effectively minimizes signal loss due to beam deviations, thereby improving communication reliability. 4.7 Discussion Upon completion of the aforementioned tests, we can assert that all parameters of our FSM are consistent with the stringent requirements necessary for laser ISLs. Here, we conducted a comparative analysis of the key parameters of various FSMs as shown in Table 2 . The selected parameters are specifically relevant to the applications in laser ISLs as mentioned in the introduction. This comparison includes typical traditional FSMs (piezoelectric ceramic FSM S-331.2 29 from PI and voice coil motor FSM from TNO 30 ), as well as MEMS FSMs that have already been employed in laser ISLs (Mirrorcle Technologies A5L2.2 31 and Hamamatsu S1227-03P 32 ). Our FSM exhibits reduced dimensions that align more effectively with the SWaP principles compared to traditional FSMs. In contrast to other MEMS FSMs, our mirror features a larger mirror size and a higher resonant frequency. In addition, our FSM stands out for its lowest nonlinearity and step response time. Also, we have a quite high level of angular resolution and repeatability accuracy. Table 2 Comparison of FSMs by key criteria Research institution Ref 29 Ref 30 Ref 31 Ref 32 This work Type Piezoelectric ceramic FSM Voice coil motor FSM Electrostatic MEMS FSM Electromagnetic MEMS FSM Piezoelectric MEMS FSM Size (mm 3 ) 14726 13253 484 540 1716 Mirror size (mm) 12.7 20 7.5 2.6 10 Maximum mechanical angle (mrad) ± 2.1 ± 17.4 ± 21 ± 130 ± 2.1 Resonant frequency (Hz) 9000 3600 559 530 1230 Nonlinearity 0.3% No data > 1% 1.3% 0.05% Angular resolution (µrad) 0.05 50 No data No data 0.3 Repeated accuracy (µrad) 3 1 No data No data 1.11 Step response (ms) 4 1 4 2 0.41 Integrated angle sensor Assembled Assembled No No Integrated 5 Conclusion This paper introduces a compact, high-performance piezoelectric MEMS FSM integrated with PZR sensors tailored for laser ISLs. The mirror features a substantial optical aperture of 10 mm and a packaged volume of 26 × 22 × 3 mm³. A novel intermediate directional defect structure is implemented to create an SCR, resulting in a 63% increase of the piezoresistive sensitivity from 3.3 mV/(V \(\:\bullet\:\) mrad) to 5.4 mV/(V \(\:\bullet\:\) mrad). The performance evaluation of the FSM encompasses various metrics, including mechanical properties, the PZR sensor characteristics, and mirror optical quality—all of which align with laser ISLs requirements. Results reveal that the FSM achieves a resonant frequency exceeding 1 kHz and exhibits low nonlinearity at 0.05% within a range of ± 2.1 mrad. Remarkably, it provides a minimum angular resolution of 0.3 µrad and repeatable positioning accuracy of 1.11 µrad, ensuring superior pointing precision. A control bandwidth of 2038 Hz is achieved through a double-step algorithm. Furthermore, the integrated angular sensor displays a nonlinearity of 0.09% at ± 1.08 mrad, a sensitivity of 5.1 mV/(V \(\:\bullet\:\) mrad), and maintains a minimum angular resolution of 0.3 µrad. Under quasi-static driving conditions (500 Hz at ± 2 mrad), the maximum dynamic deformation of the mirror surface is limited to just 2 nm. The future work will focus on the development of the MEMS FSM with a lager mirror plate to provide a broader capturing field of view for laser ISLs. Further, the close-loop control will be employed to achieve higher accuracy. Declarations Acknowledgements The authors acknowledge the support from the National Key Research and Development Program of China (No. 2023YFB3209900). Conflict of interests The authors declare no competing interests References Carlos, C., Markus, K., Joachim, H., Dionisio Diaz, G. & Paul, C. Optical inter-satellite link terminals for next generation satellite constellations. Journal 11272 , 1127203 (2020). Kaushal, H. & Kaddoum, G. Optical Communication in Space: Challenges and Mitigation Techniques. Ieee Communications Surveys and Tutorials 19 , 57-96 (2017). Lee, K., Mai, V. & Kim, H. Acquisition Time in Laser Inter-Satellite Link Under Satellite Vibrations. Ieee Photonics Journal 15 , 1-9 (2023). Li, Q. et al. Development of Multitarget Acquisition, Pointing, and Tracking System for Airborne Laser Communication. Ieee Transactions on Industrial Informatics 15 , 1720-1729 (2019). Ryan, M. et al. Implementation of laser communications acquisition function using MEMS FSM and quad detector. Journal 11993 , 1199302 (2022). Shinshi, T., Shimizu, D., Kodeki, K. & Fukushima, K. A Fast Steering Mirror Using a Compact Magnetic Suspension and Voice Coil Motors for Observation Satellites. Journal 9 (2020). Zhou, Z., Feng, Z., Xian, H. & Huang, L. Single preloaded piezoelectric-ceramic-stack-actuator-based fast steering mirror with an ultrahigh natural frequency. Appl Opt 59 , 3871-3877 (2020). Kammerer, W. et al. SSC23-WVII-04 CLICK-A: Optical Communication Experiments from a CubeSat Downlink Terminal. Journal . Grenfell, P. et al. Design and Prototyping of a Nanosatellite Laser Communications Terminal for the Cubesat Laser Infrared CrosslinK (CLICK) B/C Mission. Journal (2020). Cahoy, K.L. & Čierny, O. On-orbit beam pointing calibration for nanosatellite laser communications. Optical Engineering 58 , 041605 - 041605 (2018). Taylor, M. et al. Polar Orbiting Infrared Tracking Receiver (POINTR). Journal , 1-13 (2019). Ishola, F. & Cho, M. Experimental Study on Photodiode Array Sensor Aided MEMS Fine Steering Mirror Control for Laser Communication Platforms. Ieee Access 9 , 100197-100207 (2021). Milaševičius, M. & Mačiulis, L. A Review of Mechanical Fine-Pointing Actuators for Free-Space Optical Communication. Journal 11 (2024). Edward, H. Control of a fast steering mirror for laser-based satellite communication. (2007). Coppoolse, W., Kreienbuehl, M., Moerschell, J., Dommann, A. & Bertsch, D. Dual-axis single-mirror mechanism for beam steering and stabilisation in optical inter satellite links. 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Li, A.N. et al. Determination of Crosstalk in a Dual-Axis Piezoelectric MEMS Mirror and Suppression With Feedforward Algorithms. Ieee Sensors Journal 24 , 32272-32282 (2024). Holmstrom, S.T.S., Baran, U. & Urey, H. MEMS Laser Scanners: A Review. J Microelectromech S 23 , 259-275 (2014). Urey, H., Wine, D.W. & Osborn, T.D. Optical performance requirements for MEMS-scanner based microdisplays. Moems and Miniaturized Systems 4178 , 176-185 (2000). Ji, C.H. et al. An electrostatic scanning micromirror with diaphragm mirror plate and diamond-shaped reinforcement frame. Journal of Micromechanics and Microengineering 16 , 1033-1039 (2006). Hsu, S., Klose, T., Drabe, C. & Schenk, H. Fabrication and characterization of a dynamically flat high resolution micro-scanner. Journal of Optics a-Pure and Applied Optics 10 , 044005 (2008). Margaret, K.B. et al. Measurement of the dynamic deformation of a high-frequency scanning mirror using a Shack-Hartmann wavefront sensor. Journal 4451 , 480-488 (2001). Thakkar, P. et al. Measuring angle-resolved dynamic deformation of micromirrors with digital stroboscopic holography. 29 (2022). High-Speed Tip/Tilt Platform. https://www.pi-usa.us/fileadmin/user_upload/physik_instrumente/files/datasheets/S-331-Datasheet.pdf (2024). Kuiper, S. et al. HIGH-BANDWIDTH AND COMPACT FINE STEERING MIRROR DEVELOPMENT FOR LASER COMMUNICATIONS. Journal (2017). Gimbal-Less Two-Axis Scanning MEMS Micromirrors. https://www.mirrorcletech.com/pdf/DS/MirrorcleTech_Datasheet_A5L2.2-7500AU_S46749.pdf (2020). Ultra-miniature, high performance Electromagnetically driven laser scanning MEMS mirror. https://www.hamamatsu.com.cn/content/dam/hamamatsu-photonics/sites/documents/99_SALES_LIBRARY/ssd/s12237-03p_koth1006e.pdf (2023). Additional Declarations There is no conflict of interest Cite Share Download PDF Status: Published Journal Publication published 29 Apr, 2025 Read the published version in Microsystems & Nanoengineering → Version 1 posted Editorial decision: revise 23 Jan, 2025 Review # 3 received at journal 19 Jan, 2025 Review # 2 received at journal 15 Jan, 2025 Reviewer # 3 agreed at journal 06 Jan, 2025 Reviewer # 2 agreed at journal 01 Jan, 2025 Reviewer # 1 agreed at journal 21 Dec, 2024 Reviewers invited by journal 17 Dec, 2024 Submission checks completed at journal 15 Dec, 2024 First submitted to journal 10 Dec, 2024 Editor assigned by journal 10 Dec, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5616577","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":391422486,"identity":"6583eee6-b1d1-4db2-9609-d475a3a53492","order_by":0,"name":"Zhenyu 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1","display":"","copyAsset":false,"role":"figure","size":1151101,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eDesign of the MEMS FSM.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ea\u003c/strong\u003e Simulation structure; \u003cstrong\u003eb\u003c/strong\u003e Tip mode of x-axis; \u003cstrong\u003ec\u003c/strong\u003e Tilt mode of y-axis; \u003cstrong\u003ed\u003c/strong\u003e Piston mode; \u003cstrong\u003ee\u003c/strong\u003e The working principle of PZR sensor and silicon crystal coordination; \u003cstrong\u003ef\u003c/strong\u003e Picture of SCR under microscope; \u003cstrong\u003eg\u003c/strong\u003e Comparison of normal stress at the PZR position under the driving voltage of 90 V\u003csub\u003eDC\u003c/sub\u003e;\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-5616577/v1/59883536beaa91d24acd0fc7.png"},{"id":71904167,"identity":"a314ef44-fc99-4dc4-bcef-264d699475ea","added_by":"auto","created_at":"2024-12-19 14:55:47","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":641308,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFabrication process of the MEMS FSM\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ea\u003c/strong\u003e Fabrication process flow of MEMS FSM; \u003cstrong\u003eb\u003c/strong\u003ePhotograph of the packaged MEMS FSM; \u003cstrong\u003ec \u003c/strong\u003eDesign parameters of MEMS FSM;\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-5616577/v1/90e8be4f11a627482ef9661d.png"},{"id":71904150,"identity":"4f5ffac2-1a49-4d79-b68a-2998fb592363","added_by":"auto","created_at":"2024-12-19 14:55:45","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1329125,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eThe test schematic and the built test platform\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ea\u003c/strong\u003e Schematic diagram of the PSD test platform; \u003cstrong\u003eb \u003c/strong\u003eThe built PSD test platform; \u003cstrong\u003ec\u003c/strong\u003eSchematic diagram of the collimator test platform; \u003cstrong\u003ed\u003c/strong\u003e The built collimator test platform\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5616577/v1/dabed407df8ed68743aefb5a.png"},{"id":71904175,"identity":"f8e5d5dd-ce87-4e17-9d3e-82cde15f4755","added_by":"auto","created_at":"2024-12-19 14:55:47","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1257571,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eThe open-loop test results of the MEMS FSM\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ea\u003c/strong\u003e Resonant frequency of two axes; \u003cstrong\u003eb\u003c/strong\u003e Tilting angle linearity of two axes at full scale (±110 V); \u003cstrong\u003ec\u003c/strong\u003e Angular resolution at 16.5 mV each step; \u003cstrong\u003ed\u003c/strong\u003e Angular resolution at 13.75 mV each step; \u003cstrong\u003ee\u003c/strong\u003e Two-dimensional sweep repeatability;\u003cstrong\u003ef\u003c/strong\u003e Repeatability of zero position of two axes; \u003cstrong\u003eg\u003c/strong\u003e Tilting angle repeatability of two axes; \u003cstrong\u003eh\u003c/strong\u003e Step response of two axes; \u003cstrong\u003ei\u003c/strong\u003e Maximum operational bandwidth;\u003cstrong\u003e j\u003c/strong\u003e Tilting angle stability of two axes;\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-5616577/v1/efe09a76b44066699a676d47.png"},{"id":71904156,"identity":"dc140b95-ab78-4f81-94cc-e9dfd6d3b803","added_by":"auto","created_at":"2024-12-19 14:55:46","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":1002068,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eThe test results of the PZR sensor\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ea\u003c/strong\u003e Linearity of piezoresistive sensor at half scale (±55 V); \u003cstrong\u003eb\u003c/strong\u003e Synchronism of mechanical angle and the output voltage of piezoresistive sensor; \u003cstrong\u003ec\u003c/strong\u003e Piezoresistive output stability; \u003cstrong\u003ed\u003c/strong\u003e Angular resolution of the PZR sensor at 16.5 mV each step of FSM; \u003cstrong\u003ee\u003c/strong\u003e Angular resolution of the PZR sensor at 11 mV each step of FSM;\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-5616577/v1/491d21d43e8f1728c7961af6.png"},{"id":71904157,"identity":"aa15e5de-fb21-4c14-ab68-1dd5cc08fd11","added_by":"auto","created_at":"2024-12-19 14:55:46","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":998340,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eThe characterization of mirror dynamic deformation\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ea\u003c/strong\u003e Schematic diagram of mirror dynamic deformation; \u003cstrong\u003eb\u003c/strong\u003e FEA simulation of dynamic deformation of equivalent mass mirror model (2 mrad@500 Hz); \u003cstrong\u003ec\u003c/strong\u003e FEA simulation of dynamic deformation reinforced mirror model (2 mrad@500 Hz); \u003cstrong\u003ed \u003c/strong\u003eStatic deformation of the mirror tested by a Fizeau interferometer; \u003cstrong\u003ee\u003c/strong\u003e The experimental setup for dynamic deformation measurement; \u003cstrong\u003ef\u003c/strong\u003e Static deformation of the mirror tested by DHM; \u003cstrong\u003eg\u003c/strong\u003e Topography recorded by DHM; \u003cstrong\u003eh\u003c/strong\u003e Correcting for the tilting angle; \u003cstrong\u003ei\u003c/strong\u003e Subtracting static deformation, resulting dynamic deformation\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-5616577/v1/e286a58b6c88c9d314117bc8.png"},{"id":81610544,"identity":"d11a2f44-ff25-4c35-85b0-df7142e6c095","added_by":"auto","created_at":"2025-04-29 07:07:37","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":9393020,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5616577/v1/f226e554-fb95-40f5-9e00-4e49a5bf3cc5.pdf"}],"financialInterests":"There is no conflict of interest","formattedTitle":"A High-Performance 10mm Diameter MEMS Fast Steering Mirror with Integrated Piezoresistive Angle Sensors for Laser Inter-Satellite Links","fulltext":[{"header":"1 INTRODUCTION","content":"\u003cp\u003eIn recent years, the development of Inter-Satellite Links (ISLs) has attracted significant attention due to the increasing demands for space communication. ISLs enable high-speed data transfer between satellites, greatly enhancing the overall performance and flexibility of satellite networks\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. Laser communication technology is recognized as a key enabler for efficient ISLs, offering advantages such as higher communication capacity, wider spectrum bandwidth, lower power consumption, and enhanced resilience to interference compared with Radio Frequency (RF) communication\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. Currently, networks such as Starlink, SLILEX, LCTSX, G60, and China SatNet have already adopted laser ISLs as one of their core transmission methodologies. Laser communication terminals are anticipated to become standard communication equipment in future spacecraft payloads.\u003c/p\u003e \u003cp\u003eHowever, achieving extremely precise beam pointing poses a significant challenge in the implementation of ISLs. The Pointing, Acquisition, and Tracking (PAT) system is a core module for optical communications between satellites and between satellite and Earth\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. A Fast Steering Mirror (FSM) with high precision and optical quality is essential to the PAT system, functioning as the core device for achieving accurate beam steering in current state-of-the-art solutions\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eTraditional FSMs are typically actuated using voice coil motors or piezoelectric ceramics. Voice coil motor-based FSMs generate driving force using magnetic fields, providing significant stroke lengths, low driving voltages, and high load capacities that enhance reliability. However, these systems need improved magnetic shielding and have limited operational frequencies, which may affect their robustness\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. Piezoelectric ceramic FSMs leverage the inverse piezoelectric effect of bulk piezoelectric materials, such as PZT, to generate a driving force. While they offer strong driving force and quick response times, PZT faces challenges with impact resistance and reliability. Additionally, PZT's hysteresis requires complex driving circuits and compensation algorithms. The larger size and weight of traditional fast steering mirrors render them unsuitable for compact satellite platforms, complicating miniaturization efforts and increasing launch costs, thereby limiting mass production potential in commercial applications\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. Recently, an increasing number of research institutions have begun utilizing commercial off-the-shelf (COTS) MEMS FSMs to construct their systems. Due to their low cost, small size, lightweight, and low power consumption, the MEMS FSMs hold significant application potential in laser ISLs. For example, many institutions use an electrostatic comb-drive MEMS FSM from Mirrorcle Technologies. The CubeSat Laser Infrared CrosslinK (CLICK) mission is a technology demonstration for CubeSat optical communication terminals, focusing on downlinks and crosslinks\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. The CLICK-A 1.2U downlink terminal employs a 5 mm MEMS FSM. The results showed that the MEMS FSM was able to correct an average blind spacecraft pointing of 8.494 mrad and maintain an average RMS pointing error of 0.175 mrad after initial blind pointing error correction. Another CubeSat laser downlink demonstration mission, developed at the MIT Space Telecommunications, Astronomy, and Radiation Laboratory\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e, used a 3.6 mm MEMS FSM. Experimental results showed that beacon tracking errors of only 16 \u0026micro;rad RMS are feasible for both axes. The satellites team of the Stanford Student Space Initiative (SSI) designed and built the Polar-Orbiting Infrared Tracking Receiver (POINTR), a 1U CubeSat payload aimed to demonstrate optical-communications technology. A 4.2 mm gold-plated MEMS FSM was used on their 1U terminal and received a 0.5\u0026deg; tracking FOV\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. The Aerospace Corporation (El Segundo, USA) let their design fit within 1U with a 6.4 mm diameter MEMS FSM which enables minimization of SWaP in the laser communication terminal, which is crucial in CubeSat laser communications. The prototype was designed such that it has an acquisition FOV of 2\u0026deg; and tracking FOV of 0.5\u0026deg;, with an acquisition time measured at less than 60 seconds and a success probability exceeding 99%\u003csup\u003e5\u003c/sup\u003e. These four institutions mentioned above all used COTS MEMS FSMs from Mirrorcle Technologies. Besides these, an electromagnetically driven 3 mm Hamamatsu S1227-03P MEMS FSM was used by the Laboratory of Lean Satellite Enterprises and In-Orbit Experiments (LaSEINE) in Japan to stabilize a laser communication link on an optical bench in the laboratory. In the closed-loop mode, they used a photodiode array PDA sensor to receive stabilization for over 20 seconds despite the induced fluctuations by the vibration machine\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. Furthermore, closed-loop control can provide more stable and precise beam control, thereby improving system tracking accuracy. However, existing COTS MEMS FSMs generally lack integrated sensors and some research institutions rely on external sensors, such as the beacon detector\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e, consisting of a focal plane array (FPA) and a focusing lens assembly (LA), and the PDA sensor\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e, to construct closed-loop control systems. These approaches not only increase the overall size of the system but also lead to higher costs. Consequently, current COTS MEMS FSMs are not designed for the specific requirements of laser ISLs, exhibiting several shortcomings such as small mirror sizes, low frequency, and the lack of integrated sensors.\u003c/p\u003e \u003cp\u003eTo meet the requirements of laser ISLs, the key criteria of an FSM include\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e:(1) Size, Weight, and Power (SWaP): SWaP is the critical constraint for compact satellite platforms. The mass of FSMs typically ranges from a few grams to several kilograms, depending on the technology used and the dimensions of the mirror. Minimizing component size contributes to a more compact laser terminal, facilitating miniaturization and reducing satellite launch costs; (2) Optical/Mechanical Steering Angles: The mechanical steering angle of the mirror refers to its angular deviation from a reference position. A larger steering angle provides significant advantages for both the transmitter and receiver by expanding the field of view (FOV) necessary for effective tracking. The mechanical angle requirements for FSM in laser ISLs need to achieve at least\u0026thinsp;\u0026plusmn;\u0026thinsp;1.5 mrad; (3) Operational Bandwidth: The operational bandwidth of the FSM indicates its responsiveness to control signals and its capacity for rapid positional adjustments. For instance, the bandwidth criteria for FSM are closely linked to satellite oscillations\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e. Typically, the required bandwidths for an FSM range from several hundred Hz to over 1kHz; (4) Pointing Accuracy: Pointing accuracy is an important measure that depends on the resolution and repeatability of an FSM, which is vital for long-distance laser ISLs. Additionally, an angle sensor can provide real-time monitoring of mirror deflection angles, enabling more precise beam control through closed-loop systems. The current state-of-the-art fine beam pointing systems have pointing accuracies ranging from \u0026plusmn;\u0026thinsp;48 \u0026micro;rad to \u0026plusmn;\u0026thinsp;0.48 \u0026micro;rad\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e; (5) Mirror Surface Quality: The quality of the mirror surface, characterized by measures such as root mean square (RMS) and peak-to-valley (PV) displacements, must be minimized to ensure optimal performance. For laser ISLs, the requirement is RMS\u0026thinsp;\u0026lt;\u0026thinsp;λ/20 at λ\u0026thinsp;=\u0026thinsp;1550 nm.\u003c/p\u003e \u003cp\u003eThis study focuses on the development of a high-performance, compact MEMS FSM with a diameter of 10 mm, specifically designed for laser ISLs. It integrates an on-chip, high-sensitivity piezoresistive (PZR) sensor elements to achieve more precise beam control. The structure of this paper is as follows: Section \u003cspan refid=\"Sec2\" class=\"InternalRef\"\u003e2\u003c/span\u003e provides the design and simulation results of the mechanical structure. It also discusses the design principles of the PZR structure and optimization strategies for sensitivity. Section \u003cspan refid=\"Sec5\" class=\"InternalRef\"\u003e3\u003c/span\u003e details the fabrication process for the MEMS FSM. Section \u003cspan refid=\"Sec6\" class=\"InternalRef\"\u003e4\u003c/span\u003e presents the characterization results of the MEMS FSM, including mechanical performance, repeatability accuracy, control bandwidth, piezoresistive performance, and the dynamic deformation of the mirror surface. Additionally, at the end of this section, we perform a comparative analysis between various FSMs and the device presented in this study. Ultimately, in Section \u003cspan refid=\"Sec14\" class=\"InternalRef\"\u003e5\u003c/span\u003e, the research findings are summarized, and potential directions for future optimization are suggested.\u003c/p\u003e"},{"header":"2 Design Concept","content":"\u003cp\u003eThis study aims to develop a high-performance MEMS FSM specifically designed for laser ISLs. By optimizing the mechanical structure, this design achieves a high resonant frequency, meeting the requirement for laser ISLs above 1 kHz. In addition, while maintaining a mirror plate of 10 mm, the chip size has been significantly reduced\u003csup\u003e\u003cspan\u003e17\u003c/span\u003e\u003c/sup\u003e, increasing the fill factor. This makes the device particularly well-suited for compact satellite platforms and leads to a reduction in launch costs, making it an economically viable option for space applications. In addition, an innovative stress concentration structure is designed to improve the sensitivity of the integrated PZR sensors, enabling more precise beam control.\u003c/p\u003e\n\u003cdiv id=\"Sec3\"\u003e\n \u003ch2\u003e2.1 Design of the device structure\u003c/h2\u003e\n \u003cp\u003eTo achieve a higher fill factor and resonant frequency, this design uses a double-layered stacked structure similar to that described in our previous work\u003csup\u003e\u003cspan\u003e17\u003c/span\u003e, \u003cspan\u003e18\u003c/span\u003e\u003c/sup\u003e. The MEMS FSM consists of two parts: the actuator and the mirror. The actuator layer consists of a frame, cantilevers, springs, and a support pillar. Two pairs of cantilevers are connected to the support pillar via springs. Additionally, the support pillar is joined to the center of the 10 mm mirror plate through a wafer-level bonding process, which facilitates precise alignment and enhances structural reliability. Notably, this structure magnifies the deflecting angle of the mirror by the leverage principle.\u003c/p\u003e\n \u003cp\u003ePiezoelectric thin films are compatible with semiconductor processes, and we choose Sc-doped AlN (AlScN) film as the driving material. Although PZT has a higher piezoelectric coefficient, its hysteresis property brings a nonlinearity problem, and prolonged exposure to an electric field can lead to fatigue, adversely affecting the long-term stability of devices. The AlN film has high linearity and high reliability, but the piezoelectric coefficient is too low to satisfy the requirement of large deformation under the quasi-static operation of FSM. Therefore, in this work, AlScN film is used as the driving material, which has a higher piezoelectric coefficient along with the advantages of AlN. The AlScN film we use is doped with 20% of Sc element\u003csup\u003e\u003cspan\u003e19\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eThe optimization of the spring structure, in conjunction with finite element analysis (FEA) simulations, has led to an increased resonant frequency and a significant reduction in chip size which meet the requirement for the laser ISLs. Figure \u003cspan\u003e1\u003c/span\u003ea shows the simulation structure of the MEMS FSM with a 10 mm circular optical aperture. The fixed support point is the anchor point of the cantilever beam that connects to the frame. Figure \u003cspan\u003e1\u003c/span\u003eb-d show the FEA simulation results for the first three vibrational modes. The first mode is the tip/tilt mode of two axes with a frequency of 1253 Hz. The third mode of the MEMS FSM is the piston mode at 2827 Hz, which is increased to higher than 2 kHz. This enhancement effectively minimizes the susceptibility to critical resonant frequencies in the ambient random vibrations ranging from 20 to 2000 Hz, thereby improving the device\u0026apos;s reliability under such conditions\u003csup\u003e\u003cspan\u003e20\u003c/span\u003e\u003c/sup\u003e. Furthermore, simulations of the tilting angle indicate that the maximum tilting angle of the mirror reaches 2 mrad at an applied voltage of 90 V.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\"\u003e\n \u003ch2\u003e2.2 Design of the piezoresistive sensor\u003c/h2\u003e\n \u003cp\u003eAs shown in Fig. \u003cspan\u003e1\u003c/span\u003ee, the PZR sensor is a Wheatstone bridge consisting of four piezoresistive bars which are strategically positioned on the spring of the FSM. When the FSM tilts, the spring connecting the cantilever beam and the pillar experiences considerable normal stress. This stress induces deformation within the piezoresistive elements, leading to a change in their resistivity, which subsequently alters the output voltage of the bridge circuit. The normal stress at the piezoresistive position is directly proportional to the FSM\u0026apos;s tilting angle. Consequently, this relationship allows for real-time monitoring of the FSM\u0026apos;s position through variations in the output voltage of the Wheatstone bridge.\u003c/p\u003e\n \u003cp\u003eThe FSM employs P-type PZRs and the maximum output voltage of the PZRs can be achieved when both the cantilever beam and PZRs are oriented along the \u0026lt;\u0026thinsp;110\u0026thinsp;\u0026gt;\u0026thinsp;crystal direction. The formula for calculating the bridge output voltage is provided in the following expression:\u003c/p\u003e\n \u003cdiv id=\"Equ1\"\u003e\n \u003cdiv id=\"FileID_Equ1\" name=\"EquationSource\"\u003e$$\\:{V}_{output}=\\left(\\frac{R3}{R2+R3}-\\frac{R4}{R1+R4}\\right){V}_{input}=\\left(\\frac{1+\\frac{\\varDelta\\:R3}{R3}}{2+\\frac{\\varDelta\\:R2}{R2}+\\frac{\\varDelta\\:R3}{R3}}-\\frac{1+\\frac{\\varDelta\\:R4}{R4}}{2+\\frac{\\varDelta\\:R1}{R1}+\\frac{\\varDelta\\:R4}{R4}}\\right){V}_{input}$$\u003c/div\u003e\n \u003cdiv\u003e1\u003c/div\u003e\n \u003c/div\u003e\n \u003cp\u003e\u003cspan\u003e\u0026nbsp;\u003cspan\u003e\\(\\:{V}_{input}\\)\u003c/span\u003e\u0026nbsp;\u003c/span\u003e is the supply voltage, \u003cspan\u003e\u003cspan\u003e\\(\\:\\frac{\\varDelta\\:R}{R}\\)\u003c/span\u003e\u003c/span\u003e is the change in resistance of the PZRs at each position, expressed as:\u003c/p\u003e\n \u003cdiv id=\"Equ2\"\u003e\n \u003cdiv id=\"FileID_Equ2\" name=\"EquationSource\"\u003e$$\\:\\frac{\\varDelta\\:R}{R}={\\pi\\:}_{l,110}{\\sigma\\:}_{l}+{\\pi\\:}_{t,110}{\\sigma\\:}_{t}$$\u003c/div\u003e\n \u003cdiv\u003e2\u003c/div\u003e\n \u003c/div\u003e\n \u003cp\u003e\u003cspan\u003e\u0026nbsp;\u003cspan\u003e\\(\\:{\\pi\\:}_{l,110}\\)\u003c/span\u003e\u0026nbsp;\u003c/span\u003e and \u003cspan\u003e\u003cspan\u003e\\(\\:{\\pi\\:}_{t,110}\\)\u003c/span\u003e\u003c/span\u003e are the longitudinal and transverse piezoresistive coefficients of the PZRs oriented along the \u0026lt;\u0026thinsp;110\u0026thinsp;\u0026gt;\u0026thinsp;crystal direction. \u003cspan\u003e\u003cspan\u003e\\(\\:{\\sigma\\:}_{l}\\)\u003c/span\u003e\u003c/span\u003e and \u003cspan\u003e\u003cspan\u003e\\(\\:{\\sigma\\:}_{t}\\)\u003c/span\u003e\u003c/span\u003e are the longitudinal and transverse stresses acting on the PZR position. For P-type PZRs with a doping concentration of 1e19 cm\u003csup\u003e\u0026minus;\u0026thinsp;\u003cspan\u003e3\u003c/span\u003e\u003c/sup\u003e, \u003cspan\u003e\u003cspan\u003e\\(\\:{\\pi\\:}_{l,110}=43\\times\\:{10}^{-11}{\\text{P}\\text{a}}^{-1}\\)\u003c/span\u003e\u003c/span\u003e and \u003cspan\u003e\u003cspan\u003e\\(\\:{\\pi\\:}_{t,110}=-40\\times\\:{10}^{-11}{\\text{P}\\text{a}}^{-1}\\)\u003c/span\u003e\u003c/span\u003e\u003csup\u003e2\u003cspan\u003e1\u003c/span\u003e\u003c/sup\u003e。\u003c/p\u003e\n \u003cp\u003eHigh-sensitivity piezoresistive sensors can yield greater voltage output under the same micro-mirror rotation angle, enhancing the angular resolution of the PZRs and enabling more precise beam control. The expression for PZR sensor sensitivity is given as:\u003c/p\u003e\n \u003cdiv id=\"Equ3\"\u003e\n \u003cdiv id=\"FileID_Equ3\" name=\"EquationSource\"\u003e$$\\:S=\\frac{{V}_{output}}{{V}_{input}*{\\theta\\:}_{mech}}$$\u003c/div\u003e\n \u003cdiv\u003e3\u003c/div\u003e\n \u003c/div\u003e\n \u003cp\u003e\u003cspan\u003e\u0026nbsp;\u003cspan\u003e\\(\\:{\\theta\\:}_{mech}\\)\u003c/span\u003e\u0026nbsp;\u003c/span\u003e is the mechanical steering angle of the FSM. To enhance the sensitivity of the PZRs while maintaining the same supply voltage and doping concentration, it is essential to increase the stress experienced at the PZR position when the FSM tilts. In this study, a novel intermediate directional defect structure is designed at the front end of the cantilever beam. Figure \u003cspan\u003e1\u003c/span\u003ef depicts a micrograph of the PZR position. Four long and narrow slots are etched to create a stress concentration region (SCR). Here, we give three different structures at the PZR position. Figure \u003cspan\u003e1\u003c/span\u003eg presents the stress simulation results at the PZR position under a tilting angle of the FSM at 2 mrad. Design1 represents the baseline structure without SCR, with only relatively high stress appearing at the narrow spring position of R3. Design2 has two etched slots, concentrating stress at the position of R2 in addition to the position of R3. As shown in the figure, the stress distribution at the position of R2 appears smaller in the middle and larger on the sides. Following further optimization, Design3 introduces four slots, whose orientations are pointed to the middle, concentrating stress entirely at the position of the central PZR (R2), maximizing the PZR sensitivity. Table \u003cspan\u003e1\u003c/span\u003e provides the transverse and longitudinal stress magnitudes at the PZR position for the three designs, along with the calculated PZR sensitivity, showing a 63% improvement for Design3 compared to the initial design. Theoretically, the piezoresistive sensitivity of Design3 is 5.4 mV/(V\u003cspan\u003e\u003cspan\u003e\\(\\:\\bullet\\:\\)\u003c/span\u003e\u003c/span\u003emrad).\u003c/p\u003e\n \u003cdiv\u003e\n \u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv\u003eTable 1\u003c/div\u003e\n \u003cdiv\u003e\n \u003cp\u003ePiezoresistive sensitivity comparison of three designs\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"7\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eDesign1\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eDesign2\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eDesign3\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan\u003e\u003cspan\u003e\\(\\:{\\sigma\\:}_{l}\\)\u003c/span\u003e\u003c/span\u003e (Mpa)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan\u003e\u003cspan\u003e\\(\\:{\\sigma\\:}_{t}\\)\u003c/span\u003e\u003c/span\u003e (Mpa)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan\u003e\u003cspan\u003e\\(\\:{\\sigma\\:}_{l}\\)\u003c/span\u003e\u003c/span\u003e (Mpa)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan\u003e\u003cspan\u003e\\(\\:{\\sigma\\:}_{t}\\)\u003c/span\u003e\u003c/span\u003e (Mpa)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan\u003e\u003cspan\u003e\\(\\:{\\sigma\\:}_{l}\\)\u003c/span\u003e\u003c/span\u003e (Mpa)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan\u003e\u003cspan\u003e\\(\\:{\\sigma\\:}_{t}\\)\u003c/span\u003e\u003c/span\u003e (Mpa)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eR1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e49\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eR2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eR3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eR4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSensitivity (mV/(V\u003cspan\u003e\u003cspan\u003e\\(\\:\\bullet\\:\\)\u003c/span\u003e\u003c/span\u003emrad))\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e3.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e3.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e5.4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n\u003c/div\u003e"},{"header":"3 Fabrication","content":"\u003cp\u003eThe PZR-integrated MEMS FSM utilizes an SSD (SOI based Single piezoelectric layer Double release)-FSM process consisting of two layers: an AlScN actuator wafer and a mirror plate wafer. The AlScN actuator wafer starts with an SOI wafer with a 500 \u0026micro;m handle layer, a 1 \u0026micro;m buried oxide layer, and a 100 \u0026micro;m device layer. The mirror plate wafer needs an SOI wafer with a 450 \u0026micro;m handle layer, a 1 \u0026micro;m buried oxide layer, and a 50 \u0026micro;m device layer. The process used for its fabrication, which is suitable for 8-inch mass production, is depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea. The fabrication process of the actuator layer is divided into five main steps: (1) Firstly, a 50 nm thick silicon oxide layer is thermally oxygenated on the surface. Then, the p-type piezoresistive sensors are formed by phosphorus ion injection and thermally annealed, and the doping concentration of the piezoresistive sensors is \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\text{1\u0026times;}{\\text{10}}^{\\text{19}}\\text{/}{\\text{cm}}^{\\text{3}}\\)\u003c/span\u003e\u003c/span\u003e. However, due to the relatively low doping concentration of boron ions, further phosphorus ion implantation is required for better subsequent ohmic contacts. (2) The upper electrode Mo (200 nm), the piezoelectric layer AlScN (1.5 \u0026micro;m), and the lower electrode Mo (200 nm) were deposited on top of the oxide layer by magnetron sputtering and patterned. (3) On the top Mo layer, 500 nm silicon oxide is deposited by the PECVD (plasma enhanced chemical vapor deposition) process as a passivation layer and then dry-etched by RIE (Reactive Ion Etching) to form the electrical contact via. After that, a 1 \u0026micro;m Al layer is deposited by magnetron sputtering on the wafer and patterned to form electrical connections. (4) The 100 \u0026micro;m device layer is patterned by DRIE (Deep Reactive Ion Etching) to form the actuators and springs. Then, a 500nm Al layer is deposited by magnetron sputtering on the backside of the handle layer as a bonding metal. (5) The bonding metal and the handle layer are patterned and etched by DRIE from the back side to release all the movable parts of the device. The fabrication process of the mirror layer is divided into three main steps: (6) A 500 nm Ge layer is sputtered on the bottom silicon as the bonding layer. (7) The Ge layer is patterned for next eutectic bonding. (8) A honeycomb-shaped reinforcement structure was patterned and etched into the bottom silicon by DRIE to reduce the mass and strengthen the stiffness of the mirror plate. (9) Bond the mirror plate wafer to the actuator wafer and release the mirror. Finally, Au is magnetron sputtered as the mirror reflective layer. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb gives the photograph of the packaged MEMS FSM and Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec summarizes the final parameters of the MEMS FSM.\u003c/p\u003e "},{"header":"4 Results and discussion","content":"\u003cp\u003eAfter completing the fabrication of the device, we characterize the basic mechanical properties (including resonance frequency, mechanical tilting angle, nonlinearity, and angular resolution), pointing accuracy, open-loop control performance (including step response, operational bandwidth, and stability), PZR performance (including sensitivity, nonlinearity, stability, and angular resolution) and the dynamic deformation of the mirror.\u003c/p\u003e\n\u003cdiv id=\"Sec7\"\u003e\n \u003ch2\u003e4.1 Performance test platform\u003c/h2\u003e\n \u003cp\u003eFigure \u003cspan\u003e3\u003c/span\u003ea, b gives the Position Sensitive Detectors (PSD) test schematic and the built test platform. The laser emitted by the laser source is reflected by the mirror plate and received by the PSD, which records the position of the laser spot. When the driving signal generated by the computer acts on the MEMS FSM through the data acquisition card, the mirror will tilt, resulting in a change in the position of the laser spot. This positional change is then calculated to determine the tilting angle of the MEMS FSM and recorded by the computer. The PSD exhibits a rapid response speed and enhanced temporal resolution, resulting in superior performance in tests that require quick and sensitive dynamic responses.\u003c/p\u003e\n \u003cp\u003eHowever, PSD is sensitive to variations in ambient light and temperature, resulting in high levels of noise (\u0026gt;\u0026thinsp;10 \u0026micro;rad). To achieve a more accurate characterization of the angular resolution of the FSM and pointing accuracy, a collimator test system shown in Fig. \u003cspan\u003e3\u003c/span\u003ec, d is constructed. The collimator directs a collimated beam of light towards the mirror. As the mirror is actuated and deflecting, it alters the direction of the reflected beam. A detection system analyzes the deviation of the reflected beam. By calculating the change in beam position relative to the initial alignment, the tilting angle of the FSM can be accurately determined and recorded by the computer.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec8\"\u003e\n \u003ch2\u003e4.2 The basic mechanical performance\u003c/h2\u003e\n \u003cp\u003eInitially, we characterize the basic mechanical performance of the FSM. As shown in Fig. \u003cspan\u003e4\u003c/span\u003ea, the frequency response is assessed using Laser Doppler Velocimetry (LDV), revealing resonant frequencies of 1231.2 Hz for the x-axis and 1228.1 Hz for the y-axis, which are consistent with the simulation results. To evaluate the mechanical tilting angle and nonlinearity of the FSM, a sequence of direct current (DC) voltages ranging from \u0026minus;\u0026thinsp;110 V to +\u0026thinsp;110 V, with an increment of 11 V each step, is applied. Figure \u003cspan\u003e4\u003c/span\u003eb shows that the nonlinearities of the x-axis and y-axis measure 0.04%@\u0026plusmn;2.16 mrad and 0.05%@\u0026plusmn;2.18 mrad, which is the full-scale, the maximum driving voltage that our piezoelectric film can withstand, of the device. The nonlinearity of both axes is smaller than 0.1%, ensuring the pointing accuracy for the FSM. Additionally, the angular resolution of the FSM is tested, which is also a critical parameter for pointing accuracy. Figure \u003cspan\u003e4\u003c/span\u003ec, d shows the angular resolution results obtained using the collimator testing system. A step wave is used for driving, wherein each voltage was held for 0.5 seconds while recording data at a rate of 100 points per second. It can be observed that the minimum angular resolution of the FSM, which can be tested under the current test platform, is 0.3 \u0026micro;rad @ 16.5 mV. However, at a lower driving voltage of 13.75 mV, likely due to either the noise inherent in the testing system or limitations associated with the device itself, a smaller angular resolution could not be obtained. Such high precision is critical for maintaining accurate pointing and tracking capabilities, which ensure effective communication in dynamic environments.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec9\"\u003e\n \u003ch2\u003e4.3 Pointing Accuracy\u003c/h2\u003e\n \u003cp\u003eIn addition to nonlinearity and angular resolution, the repeatability of the FSM is another critical metric for assessing its pointing accuracy. In Fig. \u003cspan\u003e4\u003c/span\u003ee, a voltage of +\u0026thinsp;55V, +\u0026thinsp;27.5V, 0V, -27.5V, and \u0026minus;\u0026thinsp;55V is applied to both axes, randomly sampling positions in a 5\u003cspan\u003e\u003cspan\u003e\\(\\:\\times\\:\\)\u003c/span\u003e\u003c/span\u003e5 grid and repeating this process 32 times. By zooming in on one point, it can be observed that: thirty-two points are randomly distributed over a small range, 1.5 \u0026micro;rad in the x direction and 2\u0026micro;rad in the y direction. To further quantify the repeatability of the FSM, the voltage is cycled from 0V to -55V, -44V, ..., 55V back and forth 32 times for each target voltage. Whenever returning to 0V, we record the tilting angle and the triple standard deviation (3\u0026sigma;) of the 32 measurements is calculated as shown in Fig. \u003cspan\u003e4\u003c/span\u003ef. The maximum value of 3\u0026sigma; at different voltages is defined as the zero-point repeatability, yielding values of 1.11 \u0026micro;rad for the x-axis and 1.05 \u0026micro;rad for the y-axis. Similarly, in Fig. \u003cspan\u003e4\u003c/span\u003eg, the voltage is cycled from 0V to -55V, -44V, ..., 55V back and forth 32 times for each target voltage. Whenever reaching the target voltage, we record the tilting angle, and the 3\u0026sigma; of 32 measurements is calculated. The maximum value of the 3\u0026sigma; at different voltages is defined as repeatable positioning accuracy, resulting in values of 1.09 \u0026micro;rad for the x-axis and 1.04 \u0026micro;rad for the y-axis. This analysis underscores the FSM\u0026apos;s capability to achieve precise angular positioning.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec10\"\u003e\n \u003ch2\u003e4.4 Open loop control performance\u003c/h2\u003e\n \u003cp\u003eTo measure the open-loop step response of the MEMS FSM, a step voltage is applied to drive the mirror. As depicted in Fig. \u003cspan\u003e4\u003c/span\u003eh, the maximum overshoots for both axes exceed 100%, and the settling time of the step response is long under open-loop control. Therefore, a double-step feedforward control algorithm is applied to the device and the step response performance of the device. The overshoot is sharply decreased and the settling time is only 0.41ms. Thus, an open loop operational bandwidth of more than 2000 Hz can be obtained through the feedforward control algorithm\u003csup\u003e\u003cspan\u003e22\u003c/span\u003e\u003c/sup\u003e. In Fig. \u003cspan\u003e4\u003c/span\u003ei the X-axis is actuated using the feedforward control algorithm. The red line in the figure represents the driving voltage, which is a step voltage that changes upon the mirror reaching the desired angle. Throughout the experiment, nine distinct target voltages were utilized: \u0026plusmn;55 V, \u0026plusmn;\u0026thinsp;41.25 V, \u0026plusmn;\u0026thinsp;27.5 V, \u0026plusmn;\u0026thinsp;13.75 V, and 0 V, with a control cycle of 0.48 ms. A control bandwidth of 2083 Hz is achieved. The high-frequency response of FSMs allows for real-time compensation of the oscillations experienced by satellites, ensuring that the laser beam remains accurately directed at the target. Figure \u003cspan\u003e4\u003c/span\u003ej characterizes the stability of the device by independently driving each axis through a sequence of voltages: -27.5 V, -55 V, -27.5 V, 0 V, 27.5 V, and 55 V, maintaining each voltage for one hour. Under a driving voltage of 55 V, the maximum fluctuation observed within this hour was 2.8 \u0026micro;rad for the X-axis and 3.1 \u0026micro;rad for the Y-axis. The high stability is critical for ensuring the accuracy of the overall system performance.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\"\u003e\n \u003ch2\u003e4.5 PZR sensor performance\u003c/h2\u003e\n \u003cp\u003eThe integrated PZR sensors have the potential to enhance the mirror\u0026rsquo;s performance in laser ISLs by providing more precise beam control, real-time feedback, and the ability to compensate for external disturbances, ultimately leading to more reliable and efficient communication systems. Figure \u003cspan\u003e5\u003c/span\u003e presents the performance of the PZR sensors of the MEMS FSM. The PZR output signal is collected by a data acquisition card and recorded by computer. In Fig. \u003cspan\u003e5\u003c/span\u003ea, we obtain the relationship between the output voltage of the PZR sensor and the deflection angle. A sequence of DC voltages ranging from \u0026minus;\u0026thinsp;55 V to +\u0026thinsp;55 V, with increments of 11 V, are applied to the FSM. The supply voltage for the PZR sensor is set at 0.25 mV, and the output signal is amplified by a factor of 1000. The nonlinearity observed between the sensor signal and the deflection angles for the x-axis and y-axis is measured at 0.08% and 0.09%, respectively, based on the half-scale range of \u0026plusmn;\u0026thinsp;55 V for the device. The sensitivity is calculated to be 5.036 mV/(V\u003cspan\u003e\u003cspan\u003e\\(\\:\\bullet\\:\\)\u003c/span\u003e\u003c/span\u003emrad) for the x-axis and 5.024 mV/(V\u003cspan\u003e\u003cspan\u003e\\(\\:\\bullet\\:\\)\u003c/span\u003e\u003c/span\u003emrad) for the y-axis, which shows favorable agreement with the simulation result and proves that the SCR can effectively improve the sensitivity. Figure \u003cspan\u003e5\u003c/span\u003eb characterizes the synchronism between the sensor output and the deflecting angle of the FSM. A stepped waveform voltage of 550 mV each step is given to actuate the mirror, while the deflection angle and the corresponding output signal from the PZR sensor are simultaneously recorded. The result shows a good synchronism between the voltage output of the sensor and the angle. Figure \u003cspan\u003e5\u003c/span\u003ec depicts the stability test of the PZR sensor, where both axes are individually driven through the following sequence of voltages: -27.5 V, -55 V, -27.5 V, 0 V, 27.5 V, 55 V, 27.5 V, and 0 V, with each voltage maintained for one hour. The recorded PZR output signals reveal that, after amplifying the resistive signal under a 55 V drive, the maximum fluctuations observed within this hour were 1.5 mV for the x-axis and 1.2 mV for the y-axis. Figure \u003cspan\u003e5\u003c/span\u003ed, e shows the results of the angular resolution test of the PZR sensor. To achieve a smaller angular resolution, the supply voltage and amplification factor are adjusted to minimize noise in the resistive output signal. As shown in Fig. \u003cspan\u003e5\u003c/span\u003ed, when the PZR supply voltage is 1.2 V and the PZR output voltage is amplified by a factor of 200, the minimum angular resolution of the resistive sensor is 0.3 \u0026micro;[email protected] mV. Figure \u003cspan\u003e5\u003c/span\u003ee demonstrates that at a lower driving voltage of 11mV, the resistive sensor fails to respond adequately to every step change.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\"\u003e\n \u003ch2\u003e4.6 Dynamic deformation of the mirror plate\u003c/h2\u003e\n \u003cp\u003eThe rapid motion of the MEMS fast steering mirror (FSM) results in dynamic deformation of the mirror surface, as shown in Fig. \u003cspan\u003e6\u003c/span\u003ea. This dynamic deformation, defined as the deviation from linearity, can be predicted using Brosens\u0026rsquo;s formula below, which uses the unevenly distributed forces due to acceleration across the mirror surface\u003csup\u003e\u003cspan\u003e23\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003cdiv id=\"Equ4\"\u003e\n \u003cdiv id=\"FileID_Equ4\" name=\"EquationSource\"\u003e$$\\:{\\delta\\:}_{max}=0.217\\frac{\\rho\\:{f}^{2}{D}^{5}{\\theta\\:}_{mech}}{E{t}_{m}^{2}}$$\u003c/div\u003e\n \u003cdiv\u003e4\u003c/div\u003e\n \u003c/div\u003e\n \u003cp\u003ewhere \u003cspan\u003e\u003cspan\u003e\\(\\:\\rho\\:\\)\u003c/span\u003e\u003c/span\u003e is the material density, \u003cspan\u003e\u003cspan\u003e\\(\\:E\\)\u003c/span\u003e\u003c/span\u003e is the modulus of elasticity, \u003cspan\u003e\u003cspan\u003e\\(\\:f\\)\u003c/span\u003e\u003c/span\u003e is the scanner frequency, \u003cspan\u003e\u003cspan\u003e\\(\\:D\\)\u003c/span\u003e\u003c/span\u003e is the mirror aperture,\u003cspan\u003e\u003cspan\u003e\\(\\:\\:{\\theta\\:}_{mech}\\)\u003c/span\u003e\u003c/span\u003e the mechanical tilting angle, and\u003cspan\u003e\u003cspan\u003e\\(\\:\\:{t}_{m}\\)\u003c/span\u003e\u003c/span\u003e is the mirror thickness. To keep the spot diffraction limited, the maximum mechanical mirror deformation (\u003cspan\u003e\u003cspan\u003e\\(\\:{\\:\\delta\\:}_{max}\\:\\)\u003c/span\u003e\u003c/span\u003e) should not exceed \u003cspan\u003e\u003cspan\u003e\\(\\:\\lambda\\:/10\\:\\)\u003c/span\u003e\u003c/span\u003eof the shortest system wavelength\u003csup\u003e\u003cspan\u003e24\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eTo enhance resistance to static deformation, we optimized the rib shapes and sizes while maintaining the same mirror mass and ultimately, we selected a honeycomb-shaped reinforcement structure for the mirror\u003csup\u003e\u003cspan\u003e18\u003c/span\u003e\u003c/sup\u003e. Figure \u003cspan\u003e6\u003c/span\u003ed shows the static deformation of our mirror measured by a Fizeau interferometer (Zygo Verifire interferometer, America). The average PV value and RMS value of the surface figure of the devices are 87 nm and 12 nm. It is worth noting that the RMS value is merely \u0026lambda;/120 (\u0026lambda;\u0026thinsp;=\u0026thinsp;1550 nm). In addition, the reinforcement structure of the mirror also contributes to reducing dynamic deformation. Figure \u003cspan\u003e6\u003c/span\u003eb, c shows the dynamic deformation simulation results for the dynamic deformation of the mirror subjected to a tilting angle of 2 mrad at a frequency of 500 Hz. The reinforced mirror exhibits a maximum dynamic deformation of 2.15 nm, whereas the equivalent mass pure mirror model demonstrates a significantly higher maximum dynamic deformation of 9.55 nm. This indicates that the reinforced structure effectively reduces dynamic deformation by a factor of four compared to the unreinforced model.\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003ea\u003c/strong\u003e Schematic diagram of mirror dynamic deformation; \u003cstrong\u003eb\u003c/strong\u003e FEA simulation of dynamic deformation of equivalent mass mirror model (2 mrad@500 Hz); \u003cstrong\u003ec\u003c/strong\u003e FEA simulation of dynamic deformation reinforced mirror model (2 mrad@500 Hz); \u003cstrong\u003ed\u003c/strong\u003e Static deformation of the mirror tested by a Fizeau interferometer; \u003cstrong\u003ee\u003c/strong\u003e The experimental setup for dynamic deformation measurement; \u003cstrong\u003ef\u003c/strong\u003e Static deformation of the mirror tested by DHM; \u003cstrong\u003eg\u003c/strong\u003e Topography recorded by DHM; \u003cstrong\u003eh\u003c/strong\u003e Correcting for the tilting angle; \u003cstrong\u003ei\u003c/strong\u003e Subtracting static deformation, resulting dynamic deformation\u003c/p\u003e\n \u003cp\u003eCurrently, there is a limited amount of experimental research on dynamic deformation. Earlier studies measured dynamic deformation using LDV\u003csup\u003e\u003cspan\u003e25\u003c/span\u003e\u003c/sup\u003e, phase shifting interferometry\u003csup\u003e\u003cspan\u003e26\u003c/span\u003e\u003c/sup\u003e, and Shack Hartmann wavefront sensor (SHWS)\u003csup\u003e\u003cspan\u003e27\u003c/span\u003e\u003c/sup\u003e. These approaches rely on manual point measurements or offer poor lateral resolution, and they are primarily designed for dynamic deformation measurement of small mirrors (less than 2 mm in size). Recently, Silicon Austria Labs GmbH presented an approach using Digital Holographic Microscopy (DHM)\u003csup\u003e\u003cspan\u003e28\u003c/span\u003e\u003c/sup\u003e, which has high nanometric vertical resolution and compared to SHWS, much higher lateral resolution, to measure the dynamic deformation of a 2mm resonating piezoelectric MEMS mirror. In this paper, we also use the DHM R2100 from Lync ́ee Te, to measure the dynamic deformation of the MEMS FSM. The measurements are performed using an objective with a magnification of 2.5x, an NA of 0.07, and a field of view of 2.64 mm. As our 10 mm mirror plate is far beyond the field of view, a stitching mode is needed to measure such a big mirror. Figure \u003cspan\u003e6\u003c/span\u003ef is the topography of the mirror stitched by DHM at a static state. The surface topography of the FSM is basically the same as that measured by the Fizeau interferometer. According to the simulation result, under a quasi-static state (2 mrad@500 Hz), the dynamic deformation is only 2.15 nm and the surface topography of the mirror remains largely consistent with its static state. The dynamic deformation will be submerged in its own static deformation and system test noise. Therefore, we choose to measure the frequency near the resonance region while the mirror tilts at larger angles, where the mirror produces a more pronounced dynamic deformation.\u003c/p\u003e\n \u003cp\u003eAccording to the simulation result, the maximum dynamic deformation of the mirror of 35 mrad (2\u0026deg;) @1108 Hz is 181 nm. This value exceeds that of the static deformation and the system noise and can be measured by DHM. However, the vertical height of the mirror is higher than 300 \u0026micro;m, which is larger than the maximum measurable vertical height attainable by DHM. Therefore, a goniometer is needed\u003csup\u003e\u003cspan\u003e28\u003c/span\u003e\u003c/sup\u003e, as shown in Fig. \u003cspan\u003e6\u003c/span\u003ee, to manually adjust the angle of the micromirror so that the FSM is exactly perpendicular to the objective lens at 2\u0026deg; so that the vertical height difference across the mirror is within holographically measurable limits. Figure \u003cspan\u003e6\u003c/span\u003eg shows the deformation map of the mirror at 1108 Hz. The mirror has a slight angle (4 mrad) relative to the objective plane. As shown in Fig. \u003cspan\u003e6\u003c/span\u003eh, a plane is fitted to the deformation map and this residual tilt angle is added to the set angle of the goniometer to obtain a final tilt angle of 31 mrad. Figure \u003cspan\u003e6\u003c/span\u003ei gives the max dynamic deformation of the mirror of 31 mrad at 1108 Hz is 130 nm, which is basically consistent with the simulation value 161 nm. We can infer that the dynamic deformation of our MEMS FSM is less than 2 nm in the quasi-static state by characterizing the dynamic deformation under a large angle around the resonant frequency. The low dynamic deformation effectively minimizes signal loss due to beam deviations, thereby improving communication reliability.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec13\"\u003e\n \u003ch2\u003e4.7 Discussion\u003c/h2\u003e\n \u003cp\u003eUpon completion of the aforementioned tests, we can assert that all parameters of our FSM are consistent with the stringent requirements necessary for laser ISLs. Here, we conducted a comparative analysis of the key parameters of various FSMs as shown in Table \u003cspan\u003e2\u003c/span\u003e. The selected parameters are specifically relevant to the applications in laser ISLs as mentioned in the introduction. This comparison includes typical traditional FSMs (piezoelectric ceramic FSM S-331.2\u003csup\u003e29\u003c/sup\u003e from PI and voice coil motor FSM from TNO\u003csup\u003e\u003cspan\u003e30\u003c/span\u003e\u003c/sup\u003e), as well as MEMS FSMs that have already been employed in laser ISLs (Mirrorcle Technologies A5L2.2\u003csup\u003e31\u003c/sup\u003e and Hamamatsu S1227-03P\u003csup\u003e\u003cspan\u003e32\u003c/span\u003e\u003c/sup\u003e). Our FSM exhibits reduced dimensions that align more effectively with the SWaP principles compared to traditional FSMs. In contrast to other MEMS FSMs, our mirror features a larger mirror size and a higher resonant frequency. In addition, our FSM stands out for its lowest nonlinearity and step response time. Also, we have a quite high level of angular resolution and repeatability accuracy.\u003c/p\u003e\n \u003cdiv\u003e\n \u003ctable id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv\u003eTable 2\u003c/div\u003e\n \u003cdiv\u003e\n \u003cp\u003eComparison of FSMs by key criteria\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"6\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eResearch institution\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eRef 29\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eRef 30\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eRef 31\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eRef 32\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eThis work\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eType\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePiezoelectric ceramic\u003c/p\u003e\n \u003cp\u003eFSM\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVoice coil motor\u003c/p\u003e\n \u003cp\u003eFSM\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eElectrostatic\u003c/p\u003e\n \u003cp\u003eMEMS FSM\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eElectromagnetic\u003c/p\u003e\n \u003cp\u003eMEMS FSM\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePiezoelectric\u003c/p\u003e\n \u003cp\u003eMEMS FSM\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSize (mm\u003csup\u003e\u003cspan\u003e3\u003c/span\u003e\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e14726\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13253\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e484\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e540\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1716\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMirror size (mm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e12.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMaximum mechanical angle (mrad)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u0026thinsp;2.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u0026thinsp;17.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u0026thinsp;21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u0026thinsp;130\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026plusmn;\u0026thinsp;2.1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eResonant frequency (Hz)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3600\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e559\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e530\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1230\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNonlinearity\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNo data\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026gt;\u0026thinsp;1%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.3%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.05%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAngular resolution (\u0026micro;rad)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNo data\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNo data\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eRepeated accuracy (\u0026micro;rad)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNo data\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNo data\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.11\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eStep response (ms)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.41\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eIntegrated angle sensor\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAssembled\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAssembled\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eIntegrated\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n\u003c/div\u003e"},{"header":"5 Conclusion","content":"\u003cp\u003eThis paper introduces a compact, high-performance piezoelectric MEMS FSM integrated with PZR sensors tailored for laser ISLs. The mirror features a substantial optical aperture of 10 mm and a packaged volume of 26 \u0026times; 22 \u0026times; 3 mm\u0026sup3;. A novel intermediate directional defect structure is implemented to create an SCR, resulting in a 63% increase of the piezoresistive sensitivity from 3.3 mV/(V\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\bullet\\:\\)\u003c/span\u003e\u003c/span\u003emrad) to 5.4 mV/(V\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\bullet\\:\\)\u003c/span\u003e\u003c/span\u003emrad). The performance evaluation of the FSM encompasses various metrics, including mechanical properties, the PZR sensor characteristics, and mirror optical quality\u0026mdash;all of which align with laser ISLs requirements. Results reveal that the FSM achieves a resonant frequency exceeding 1 kHz and exhibits low nonlinearity at 0.05% within a range of \u0026plusmn;\u0026thinsp;2.1 mrad. Remarkably, it provides a minimum angular resolution of 0.3 \u0026micro;rad and repeatable positioning accuracy of 1.11 \u0026micro;rad, ensuring superior pointing precision. A control bandwidth of 2038 Hz is achieved through a double-step algorithm. Furthermore, the integrated angular sensor displays a nonlinearity of 0.09% at \u0026plusmn;\u0026thinsp;1.08 mrad, a sensitivity of 5.1 mV/(V\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\bullet\\:\\)\u003c/span\u003e\u003c/span\u003emrad), and maintains a minimum angular resolution of 0.3 \u0026micro;rad. Under quasi-static driving conditions (500 Hz at \u0026plusmn;\u0026thinsp;2 mrad), the maximum dynamic deformation of the mirror surface is limited to just 2 nm. The future work will focus on the development of the MEMS FSM with a lager mirror plate to provide a broader capturing field of view for laser ISLs. Further, the close-loop control will be employed to achieve higher accuracy.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors acknowledge the support from the National Key Research and Development Program of China (No. 2023YFB3209900).\u003c/p\u003e\n\u003cp\u003eConflict of interests\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eCarlos, C., Markus, K., Joachim, H., Dionisio Diaz, G. \u0026amp; Paul, C. Optical inter-satellite link terminals for next generation satellite constellations. \u003cem\u003eJournal\u003c/em\u003e \u003cstrong\u003e11272\u003c/strong\u003e, 1127203 (2020).\u003c/li\u003e\n\u003cli\u003eKaushal, H. \u0026amp; Kaddoum, G. 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HIGH-BANDWIDTH AND COMPACT FINE STEERING MIRROR DEVELOPMENT FOR LASER COMMUNICATIONS. \u003cem\u003eJournal\u003c/em\u003e (2017).\u003c/li\u003e\n\u003cli\u003eGimbal-Less Two-Axis Scanning MEMS Micromirrors. https://www.mirrorcletech.com/pdf/DS/MirrorcleTech_Datasheet_A5L2.2-7500AU_S46749.pdf (2020).\u003c/li\u003e\n\u003cli\u003eUltra-miniature, high performance Electromagnetically driven laser scanning MEMS mirror. https://www.hamamatsu.com.cn/content/dam/hamamatsu-photonics/sites/documents/99_SALES_LIBRARY/ssd/s12237-03p_koth1006e.pdf (2023).\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"microsystems-and-nanoengineering","isNatureJournal":false,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"micronano","sideBox":"Learn more about [Microsystems \u0026 Nanoengineering](http://www.nature.com/micronano/)","snPcode":"41378","submissionUrl":"https://mts-micronano.nature.com/","title":"Microsystems \u0026 Nanoengineering","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"MEMS FSM, Piezoresistive Sensor, Laser Inter-satellite Link, Quasi-Static, Dynamic Deformation","lastPublishedDoi":"10.21203/rs.3.rs-5616577/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5616577/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis paper presents a compact and high-performance piezoelectric Micro-Electro-Mechanical System (MEMS) Fast Steering Mirror (FSM) designed for use in laser Inter-Satellite Links (ISLs). The FSM features a large optical aperture of 10 mm and is batch fabricated using an 8-inch wafer-level eutectic bonding process, packaged into a volume of 26 × 22 × 3 mm\u003csup\u003e3\u003c/sup\u003e. Notably, the piezoresistive (PZR) sensor is integrated on the spring of the FSM to facilitate precise beam control. Furthermore, an intermediate directional defect structure is novelly designed to create a Stress Concentration Region (SCR), effectively improving PZR sensitivity from 3.3 mV/(V·mrad) to 5.4 mV/(V·mrad). In this article, various performance metrics of the FSM are tested, including the mechanical characteristics, PZR sensor properties, and mirror optical quality, which all meet the requirements for laser ISLs. Results indicate that the FSM achieves a high resonant frequency (\u0026gt;1 kHz) and a low nonlinearity of 0.05%@±2.1 mrad. A remarkable minimum angular resolution of 0.3 μrad and a repeated positioning accuracy of 1.11 μrad ensure exceptional pointing precision. The open-loop control is driven by the double-step algorithm, resulting in a step response time of 0.41 ms and achieving a control bandwidth over 2 kHz. Additionally, the integrated angular sensor demonstrates a nonlinearity of 0.09%@±1.05 mrad, a sensitivity of 5.1 mV/(V·mrad), and a minimum angular resolution of 0.3 μrad. Under quasi-static driven conditions (500 Hz @±2 mrad), the maximum dynamic deformation of the mirror surface is merely 2 nm.\u003c/p\u003e","manuscriptTitle":"A High-Performance 10mm Diameter MEMS Fast Steering Mirror with Integrated Piezoresistive Angle Sensors for Laser Inter-Satellite Links","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-12-19 14:55:39","doi":"10.21203/rs.3.rs-5616577/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"revise","date":"2025-01-24T03:27:00+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"This content is not available.","date":"2025-01-20T01:27:20+00:00","index":3,"fulltext":"This content is not available."},{"type":"editorInvitedReview","content":"This content is not available.","date":"2025-01-15T10:17:11+00:00","index":2,"fulltext":"This content is not available."},{"type":"reviewerAgreed","content":"This content is not available.","date":"2025-01-06T06:38:38+00:00","index":3,"fulltext":"This content is not available."},{"type":"reviewerAgreed","content":"This content is not available.","date":"2025-01-02T04:24:57+00:00","index":2,"fulltext":"This content is not available."},{"type":"reviewerAgreed","content":"This content is not available.","date":"2024-12-21T11:28:31+00:00","index":1,"fulltext":"This content is not available."},{"type":"reviewersInvited","content":"","date":"2024-12-17T13:28:56+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-12-16T00:55:44+00:00","index":"","fulltext":""},{"type":"submitted","content":"Microsystems \u0026 Nanoengineering","date":"2024-12-10T12:24:38+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-12-10T12:24:38+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"microsystems-and-nanoengineering","isNatureJournal":false,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"micronano","sideBox":"Learn more about [Microsystems \u0026 Nanoengineering](http://www.nature.com/micronano/)","snPcode":"41378","submissionUrl":"https://mts-micronano.nature.com/","title":"Microsystems \u0026 Nanoengineering","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"56cf1519-4559-45ea-acff-528903039258","owner":[],"postedDate":"December 19th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-04-29T07:07:28+00:00","versionOfRecord":{"articleIdentity":"rs-5616577","link":"https://doi.org/10.1038/s41378-025-00935-1","journal":{"identity":"microsystems-and-nanoengineering","isVorOnly":false,"title":"Microsystems \u0026 Nanoengineering"},"publishedOn":"2025-04-29 04:00:00","publishedOnDateReadable":"April 29th, 2025"},"versionCreatedAt":"2024-12-19 14:55:39","video":"","vorDoi":"10.1038/s41378-025-00935-1","vorDoiUrl":"https://doi.org/10.1038/s41378-025-00935-1","workflowStages":[]},"version":"v1","identity":"rs-5616577","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5616577","identity":"rs-5616577","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}