Heterogeneously Integrated Micro-ring with SnS₂ for Dual-functional Optical Modulation and Photodetection

Heterogeneously Integrated Micro-ring with SnS₂ for Dual-functional Optical Modulation and Photodetection | 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 Heterogeneously Integrated Micro-ring with SnS₂ for Dual-functional Optical Modulation and Photodetection Lianqing Zhu, yi Du, Lidan Lu, Bofei Zhu, Bowen Bo, Yingjie Xu, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7048954/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Dual-functional devices capable of simultaneous modulation and photodetection offer enhanced flexibility for on-chip photonic integrated systems. However, fabricating such dual-functional devices remains challenging due to process compatibility issues, device instability, and insufficient light-matter interaction enhancement. As two-dimensional materials exhibit unique advantages in on-chip heterogeneously integrated photonic devices, particularly modulators and photodetectors, we demonstrate a dual-functional few-layer SnS 2 integrated above a silicon-on-insulator (SOI) micro-ring resonator. By the electrode-engineered design, we achieve simultaneous light modulation and detection without external gate control or heterojunctions, which significantly simplifies fabrication procedures. The device achieves modulation depth of 23 dB and exhibits hot-carrier-assisted infrared photodetection with the responsivity of 0.38 A/W at a bias voltage of − 2 V. This integrated architecture can not only reduce the footprints of photonic integrated circuits but also facilitate the real-time monitoring of modulation states via electrical feedback, thereby enhancing operation stability of the on-chip photonic computing systems. Physical sciences/Optics and photonics/Optical materials and structures/Silicon photonics Physical sciences/Optics and photonics/Applied optics/Optoelectronic devices and components Physical sciences/Optics and photonics/Applied optics/Integrated optics Figures Figure 1 Figure 2 Figure 3 Figure 4 1. Introduction In optical neural network systems, input optical power is monitored by a PD in an optical bypass, and the photocurrent is transferred to the modulation voltage of a modulator to form a feedback circuit, finally tuning the transmitted optical power. Such a strategy brings higher power consumption and time delay because of the opto-electric conversion 1 . Therefore, with optical modulation and detection in one device, the device footprint is smaller than other on-chip strategies. Research on dual-functional devices based on heterogeneous integration of two-dimensional materials with waveguides delivers lower power consumption, broader bandwidth, and enhanced integration density for optical computing network architectures 2 , 3 , propelling photonic computing technologies toward high-performance computing and future network systems. This approach not only optimizes current network frameworks but also provides efficient optical solutions for diverse future computing demands. Integrating two-dimensional materials with waveguides enables dual-function devices capable of simultaneous modulation and photodetection, reducing inter-device connections and thereby optimizing optical circuit layout and design 4 . Such highly integrated components diminish photonic network complexity while enabling more flexible and compact optical routing. The atomic-scale thickness and exceptional optoelectronic properties of 2D materials facilitate efficient optical modulation and detection under low bias voltages, significantly enhancing system integration density. When incorporated into silicon photonics platform, these materials demonstrate outstanding performance in detectors, modulators, and memristive devices 5 – 8 . Owing to their high photosensitivity, heterogeneously integrated 2D materials enable broadband photodetection across diverse waveguide platforms through photoconductive, thermoelectric, and plasmonic mechanisms 9 – 11 . For modulation functionality, this integration leverages the tunable Fermi levels of 2D materials, capacitive configurations, or thermal effects. Reported materials enabling waveguide-integrated modulation include graphene 12 – 14 , black phosphorus (BP) 15 , 16 , PtSe 2 17 , et. al. As widely demonstrated in graphene and TMDCs, an out-of-plane electric field could modify their electronic structures remarkably due to the strong vertical confinements of wave functions 18 . Similarly, BP thin films could be considered as a quantum well, whose band edge allows a reliable electrical engineering to change the optical responses 19 . However, most reported dual-functional devices are graphene-based 1 – 3 , which necessitates the use of monolayer graphene and requires the formation of capacitive structures or heterojunctions to achieve modulation functionality. This imposes stringent process requirements on device fabrication. In this work, we hybrid integrate SnS 2 onto a micro-ring resonator (MRR) to demonstrate a single device that can simultaneously function as an optical modulator and a photodetector. This device operates without requiring monolayer-specific 2D materials, capacitive heterostructures, or external gating. In this compact device architecture, SnS 2 acts as the primary photoactive material, enabling photon-to-electron conversion for photodetection while simultaneously mitigating light-transmission perturbations induced by Au heating electrodes. Furthermore, the engineered Au electrode design facilitates efficient hot-carrier generation 20 . On one hand, the micro-ring resonator's strong optical confinement enhances light-matter interactions with the 2D material, enabling infrared photodetection through hot-carrier assistance. On the other hand, localized refractive index modulation via the heating electrode delivers optical modulation functionality. The dual-functional device achieves 23 dB modulation depth in the C-band and exhibits sensitive photoresponse with 0.38 A/W responsivity at − 2 V. This heterogeneously integrated platform eliminates dependence on monolayer graphene and requires no gate electrodes. Its design flexibility enables deployment as reconfigurable optical elements in on-chip photonic computing systems. Concurrent optical modulation and real-time electrical readout through dual ports permit in-situ monitoring of modulation states, paving the way for ultra-compact integrated photonic circuits. 2. Results 2.1. Device fabrication and characterization Conventional approaches for dual-function devices rely on graphene-based capacitors, FETs, or heterojunctions, where an out-of-plane electric field shifts the band edge to enable functionality. These architectures exhibit critical dependence on graphene thickness and require precise capacitor/heterojunction fabrication 1 – 3 . In contrast, our design eliminates thickness constraints for SnS₂ and operates without external gate bias, significantly reducing process complexity. Figure 1 (a) illustrates the dual functional device of SnS 2 integrated on a micro-ring resonator. Direct deposition of gold thin films onto the waveguide for thermal modulation induces substantial optical propagation losses, ultimately resulting in the complete quenching of resonant peaks. Therefore, we deploy a two-dimensional (2D) material as an interlayer between the waveguide and the thermally active gold film. This configuration simultaneously attenuates the detrimental influence of the gold heater on the optical transmission characteristics of the micro-ring resonator. Fundamentally, achieving infrared photoresponse in wide-bandgap SnS₂ (E g ≈ 2.07 eV) presents a significant challenge 21 , 22 . Here, we overcome this limitation through hot-carrier-assisted detection enabled by micro-ring-enhanced light-matter interactions. At the same time, the wide-bandgap 2D material SnS 2 exhibits minimal absorption cross-section within the infrared spectrum, implying negligible perturbation to resonant cavity transmission. Crucially, the incorporation of this photoactive material is indispensable for enabling photodetection functionality. The SnS 2 was mechanically exfoliated onto the silicon waveguide. Au electrodes (80-nm-thick) were fabricated through lift-off process. All the waveguide structures were fabricated by electron beam lithography (EBL) and inductively coupled plasma (ICP) etching processes. A schematic of the dual-function device architecture is shown in Fig. 1 (a). Electrodes A and B were patterned atop the waveguide and SnS 2 layer for optical modulation, while electrode C—positioned remotely from the waveguide and modulation electrodes—contacts SnS 2 exclusively for photodetection. Figure 1 (b) and Fig. 1 (d) show the SnS 2 thickness of 18.8 nm measured using atomic force microscopy (AFM). Figure 1 (c) shows the Raman spectrum of SnS 2 within the integrated device exhibits characteristic vibrational modes at 315 cm − 1 . 23 2.2. Thermo-optic modulation operation In order to characterize the effect of Al 2 O 3 , SnS 2 and Au electrodes deposition on the ring resonator, the transmission spectrum of the ring resonator in each step was measured and shown in Fig. 2 (a). As can be seen, the transmission spectrum exhibits increased loss after the deposition of the thin gold layer, while the extinction ratio shows no significant change. The extra loss is due to the fact that the gold layer introduces additional absorption. Specifically, the top Au electrode absorbs the evanescent field of the waveguide mode in the telecom band, particularly when a DC voltage is applied between electrode A and electrode B for optical modulation, which generates considerable hot electrons. During device characterization, we monitored the current variation between heating electrodes A and B under different DC voltages (Fig. 2 c). At 6 V applied bias, the modulation electrodes risk thermal breakdown. To ensure low-power operation and prevent electrode failure, we maintained the loop current below 0.05 A. With DC voltages of 0.5-1 V applied between electrodes A and B, the transmission spectrum evolution is shown in Fig. 2 (b). We observe a red shift of the resonant notch while the extinction ratio remains statistically unchanged. At the resonant wavelength of 1549.76 nm, the device exhibits an extinction ratio of 24 dB and a 3-dB bandwidth of 0.52 nm, corresponding to a quality factor (Q) of 2980. Under the bias of 0.8 V, a modulation depth of 23 dB is achieved. Increasing the bias from 0 to 0.8 V induces a 1.8 nm red shift, consuming 38 mW electrical power. The thermo-optic tuning efficiency is calculated as 0.047 nm/mW. When a bias voltage is applied between electrodes A and B, hot electrons are generated and tunnel into the conduction band of the SnS₂ layer. These hot electrons collide with intrinsic carriers in SnS₂, but ultimately lose energy via electron-phonon scattering, increasing the lattice temperature. This process is dominated by the thermo-optic effect, inducing a redshift in the transmission spectrum. The resonant wavelength shift (Δλ) relates to the effective refractive index change (Δ N eff ) through Eq. ( 1 ): Where n g and λ 0 are real part of the group index and resonant wavelength, respectively. Δ N eff exhibits a linear dependence on waveguide temperature, inducing a thermo-optic redshift in the transmission spectrum upon heating. The corresponding resonant wavelength shifting vs power is shown in Fig. 2 (d). Given the linear relationship between temperature and power (T∝P), Equations ( 1 ) and ( 2 ) collectively demonstrate that the resonant wavelength shift scales proportionally with applied power (Δλ∝P). Then, we measured the the dynamic response of the modulator (shown as in Fig. 2 e). The rise time (from 10–90%) was 3.4 µs and the decay time (from 90–10%) was 6.9 µs. The rise time was decided by the heating speed powered by the DC voltage applied across the thermal electrodes, whereas the decay time by the cooling speed. 2.3. Hot-carrier-assisted photodetection operation Under non-modulated conditions (U ab =0 V), we measured the current (I bc ) between electrode B and electrode C as a function of bias voltage. By coupling light at a wavelength of 1549.7 nm into the waveguide, photocurrents are observed, as the I-V curves shown in Fig. 3 (a), which are obtained at different incident optical powers. When light is coupled into the waveguide toward the Au/SnS 2 interface, the rectifying I-V characteristics demonstrate asymmetric behavior about zero bias, confirming back-to-back Schottky barrier formation. Band engineering analysis reveals that this photoresponse originates from the interfacial energy band alignment depicted in Fig. 3 (b). The work function of Au at equilibrium ensures Fermi-level alignment with the n-type SnS 2 (i). The energy band diagrams of the device under U bc >0 V (ii) and U bc < 0 V (iii) reveal the physical origin of the I-V characteristics. Waveguide evanescent field excitation at the metal electrode generates non-equilibrium hot electrons. At zero bias, the built-in electric field of the Au/SnS 2 Schottky junction enables hot electron injection into SnS 2 , with subsequent diffusion-driven transport to electrode C. Under U bc >0 V, the applied electric field drives directional drift of these carriers from electrode B through the SnS2 channel to electrode C. Conversely, U bc < 0 V establishes a reverse field that blocks hot electron injection from electrode B into SnS 2 . Besides, due to the exitance of the micro-ring resonator, the interaction between light and SnS 2 is enhanced since the light penetrates multiple times and interacts with SnS 2 , and the thermal carriers generated by lattice vibrations, eventually generate current under bias voltage. Experimental results show that the SnS 2 device exhibits a dark current of 41.7 nA at − 2 V bias. As shown in Fig. 3 (c), when a 1550 nm light source with 0.1 µW optical power is coupled into the waveguide through the grating, the device demonstrates a photoresponsivity of 0.38 A/W under − 2 V bias. Notably, the responsivity increases with the applied bias voltage. In Fig. 3 (d), the measured 10–90% rise time and 90–10% fall time are 8.4 ms and 11.8 ms, respectively. 2.4. Mechanism of synergistic current dynamics in dual-mode operation Additionally, under modulated conditions with DC bias applied between electrode A and electrode B, the output current between electrode B and electrode C was measured while coupling 1549.7 nm laser light into the waveguide. Figure 4 (a) shows the equivalent circuit for synchronous optical modulation and detection. The corresponding results are shown in Fig. 4 (b). These results indicate that applying different voltages between electrodes A and B affects the output current between electrodes B and C. Figure 4 (c) shows that increasing U ab enhances output current I when U bc 0 V (Fig. 4 (d)). This phenomenon arises from the superposition of currents under bias. When U bc <0 V (defined as current flowing from electrode C to electrode B), U ab induces local heating at the Au electrode, generating hot electrons. The resulting thermal gradient drives a diffusion current (I diff ) in the same direction (electrode C to electrode B). The total current is given by: I = I diff +I bc , where I bc is the baseline current at U ab = 0 V (note: denotes the current flow direction). As U ab increases, I diff increases, leading to an enhancement of the total current I under negative U bc . Conversely, when U bc >0 V, the total current becomes: I = I bc −I diff . Here, an increase in U ab enhances I diff , but since I diff flows opposite to I bc , the net current I decreases. This dual-functional device uniquely integrates optical modulation and real-time photocurrent readout through its dual-port electrode design—a paradigm distinct from conventional approaches. Crucially, the output current at the detection port (Electrodes B/C) provides in situ monitoring of the modulation state. By establishing the correlation between modulation voltage (Electrodes A/B) and output current, we demonstrate a voltage-to-current feedback mechanism. When deployed in on-chip optical computing systems, this enables real-time crosstalk monitoring between devices, thereby enhancing computational accuracy through dynamic feedback control. It should be noted that our device is not designed for high-frequency operation, which would need further optimization of electrical contacts on the device in order to reduce the associated resistive‐capacitive 10 time constant of the RC circuit. Reducing the contact resistance as well as capacitance allows the devices to work over GHz. 3. Discussion In summary, we demonstrate a compact SnS₂-based dual-functional device integrated with a micro-ring resonator that simultaneously achieves optical modulation and photodetection through strategic electrode design, eliminating the need for conventional gate-voltage control or heterojunction structures and thereby significantly simplifying fabrication. The device achieves 23 dB modulation depth and exhibits hot-carrier-assisted infrared photodetection with the responsivity of 0.38 A/W at − 2 V bias. This design paradigm, applicable to diverse 2D materials, extends their silicon photonics utility while addressing next-generation computing needs. It enables real-time modulation-state monitoring via photocurrent readout (Electrodes B/C) and enhances system stability through feedback-driven crosstalk suppression—establishing a scalable pathway to robust multifunctional photonic integrated circuits. 4. Materials and methods 4.1 Waveguide fabrication The bottom layer includes a ring resonator with grating couplers on a silicon-on-insulator (SOI) platform with 220 nm device layer, the height of the ridge waveguide 70 nm, and the slab of 150 nm. Both the straight and ring waveguide have a width of 450 nm and the gap between them is 100 nm. A pair of tapered gratings was designed at both ends of the straight waveguide for efficient coupling for TE mode. All these structures were fabricated by electron beam lithography (EBL) and inductively coupled plasma (ICP) etching processes. Then, the 10 nm thick aluminum oxide (Al 2 O 3 ) dielectric layer between the SOI platform and the SnS 2 is deposited by atomic layer deposition (ALD) which acts as an electrical isolation layer. After this, another step of e-beam lithography isdone to define the metal electrodes. The electrodes are made by evaporating 80 nm of Au using an evaporator and lift-off process. 4.2 TMDC fabrication Bulk flakes of SnS 2 (Shenzhen Six Carbon Technology Co., Ltd.) are exfoliated via the Scotch tape method onto polydimethylsiloxane (PDMS). Next, the target flakes are found using an optical microscope and transferred to the intended waveguide by dry transfer technique. 4.3 Device measurements Device characterization was performed on an edge-coupling platform with polarization-maintaining fibers. Tunable laser light (1520–1620 nm) was coupled into the waveguide via a high-precision alignment stage. Thermo-optic modulation was driven by a programmable DC source (Keysight B2912A) providing bias voltages to Electrodes A/B. Temporal response of the modulation function was captured using a waveform generator and a real-time oscilloscope (Lecroy, 740Zi-A). Photodetection metrics including I-V characteristics and response time were quantified using a semiconductor parameter analyzer (Keysight B1500A) under tunable laser (TUNICS T100S-HP). Declarations Conflict of interest The authors have no conflicts to disclose. Acknowledgement This research was funded by the National Natural Science Foundation of China (62205029); the National Key Research and Development Sub project (2022YFF0705801); the Young Elite Scientists Sponsorship Program by CAST (2022QNRC001). References Zhong, C. et al. Graphene/silicon heterojunction for reconfigurable phase-relevant activation function in coherent optical neural networks. Nature Communications 14 , 6939, doi:10.1038/s41467-023-42116-6 (2023). Wu, J. et al. Dual-function optical modulation and detection in microring resonators integrated graphene/MoTe2 heterojunction. Applied Physics Reviews 11 , doi:10.1063/5.0207874 (2024). Youngblood, N., Anugrah, Y., Ma, R., Koester, S. J. & Li, M. 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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-7048954","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":497000767,"identity":"5fe815bc-bd69-4a37-a468-e08163e3a323","order_by":0,"name":"Lianqing Zhu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA10lEQVRIie3RPQrCMBTA8VeEdHnoGqnQK0SEbNKrtBTaVXFyE4ROghcQvILeQHjYMwh2KAiZXNw6iBiLiFNaN4f8h2TJj3wB2Gx/WBeA6emAenBKEC0I+xAGHfETeU2MtzoYc1N1QSgG/nYl59Wk8MGl485IsExHCApFjvKMQg0XmCQnI+Fh7iEQCqYJCHIWHGUDibKa+BnKaSUoaEFiVhPQBwMUFDUTVKy/qe+SzDxN4qzpLj39YvwKReAvaX+r7jReu5QbCUCov/3xva95+ZvYbDabzdgT/CY/eDnaWAwAAAAASUVORK5CYII=","orcid":"","institution":"Beijing Information Science and Technology University","correspondingAuthor":true,"prefix":"","firstName":"Lianqing","middleName":"","lastName":"Zhu","suffix":""},{"id":497000768,"identity":"ed9afc6c-d6e7-4149-a880-13a561843f74","order_by":1,"name":"yi Du","email":"","orcid":"https://orcid.org/0000-0001-8302-8890","institution":"Beijing Information Science and Technology University","correspondingAuthor":false,"prefix":"","firstName":"yi","middleName":"","lastName":"Du","suffix":""},{"id":497000769,"identity":"ad4902ed-6b8b-4a64-9779-92445614214e","order_by":2,"name":"Lidan Lu","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Lidan","middleName":"","lastName":"Lu","suffix":""},{"id":497000770,"identity":"1d336719-78c7-4dae-ab53-356e1995fe6d","order_by":3,"name":"Bofei Zhu","email":"","orcid":"","institution":"Tsinghua University","correspondingAuthor":false,"prefix":"","firstName":"Bofei","middleName":"","lastName":"Zhu","suffix":""},{"id":497000771,"identity":"138d38d8-57bc-40f0-be05-458fab250203","order_by":4,"name":"Bowen Bo","email":"","orcid":"","institution":"Beijing Information Science and Technology University","correspondingAuthor":false,"prefix":"","firstName":"Bowen","middleName":"","lastName":"Bo","suffix":""},{"id":497000772,"identity":"a6541f9e-b808-414b-92a2-fe8210a06cba","order_by":5,"name":"Yingjie Xu","email":"","orcid":"","institution":"Hefei University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Yingjie","middleName":"","lastName":"Xu","suffix":""},{"id":497000773,"identity":"87615329-376e-4d54-9f2e-4eae8c979afe","order_by":6,"name":"Guang Chen","email":"","orcid":"","institution":"Beijing Information Science and Technology University","correspondingAuthor":false,"prefix":"","firstName":"Guang","middleName":"","lastName":"Chen","suffix":""},{"id":497000774,"identity":"50845139-056a-4298-8a69-8997095224a1","order_by":7,"name":"Guanghui Ren","email":"","orcid":"https://orcid.org/0000-0002-9867-8279","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Guanghui","middleName":"","lastName":"Ren","suffix":""},{"id":497000775,"identity":"c8bb6b37-4c7c-4af0-bba6-1aab817d128d","order_by":8,"name":"Xiaoping Lou","email":"","orcid":"","institution":"Beijing Information Science and Technology University","correspondingAuthor":false,"prefix":"","firstName":"Xiaoping","middleName":"","lastName":"Lou","suffix":""},{"id":497000776,"identity":"ec7daf91-4a28-470e-893a-8d026362cf0c","order_by":9,"name":"Mingli Dong","email":"","orcid":"","institution":"Beijing Information Science and Technology University","correspondingAuthor":false,"prefix":"","firstName":"Mingli","middleName":"","lastName":"Dong","suffix":""},{"id":497000777,"identity":"dea84909-6f0e-40ce-8608-3390a5d76123","order_by":10,"name":"Zheng You","email":"","orcid":"https://orcid.org/0000-0002-3941-1371","institution":"Tsinghua University, China","correspondingAuthor":false,"prefix":"","firstName":"Zheng","middleName":"","lastName":"You","suffix":""}],"badges":[],"createdAt":"2025-07-04 18:15:14","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7048954/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7048954/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":88922899,"identity":"76ff0b08-2e1f-4cb8-b81e-7ed38e658c10","added_by":"auto","created_at":"2025-08-12 17:56:53","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":163477,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Dual-function device architecture for optical modulation and photodetection based on SnS\u003csub\u003e2\u003c/sub\u003e integrating with an micro-ring resonator (MRR), light is guided in/out by two opposite grating couplers. (b) AFM image of the device. (c) Raman spectrum of SnS\u003csub\u003e2\u003c/sub\u003e film. (d) AFM height of the 18.8 nm SnS\u003csub\u003e2\u003c/sub\u003e flake.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7048954/v1/f28d24e909eebf14ce1371df.png"},{"id":88924488,"identity":"2b3f2a5e-2dd7-417d-8051-4242818496ac","added_by":"auto","created_at":"2025-08-12 18:28:53","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":142707,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Measured transmission spectra of the MRR after each step of transfer. (b) Transmission spectra of an MRR integrating with Au/SnS2 under different bias voltages. (c) Current variation between electrode A and electrode B as a function of DC voltage. (d) Resonance wavelength shifts with electric power. (e) Response Time of Thermal Tuning.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7048954/v1/e9bed47660278e2fcab877cd.png"},{"id":88922900,"identity":"a6c45705-0abe-4398-a3c8-ddc34adf615e","added_by":"auto","created_at":"2025-08-12 17:56:53","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":129052,"visible":true,"origin":"","legend":"\u003cp\u003e(a) I\u003csub\u003ebc\u003c/sub\u003e-V\u003csub\u003ebc\u003c/sub\u003e characteristics under the different power of 1550 nm laser. Inset: Measured Equivalent Circuit. (b) A schematic energy band diagram explains the photodetection mechanism under the equilibrium state, under U\u003csub\u003ebc\u003c/sub\u003e\u0026lt; 0 V and under U\u003csub\u003ebc\u003c/sub\u003e \u0026gt; 0 V, (c) The responsivity of the Au/SnS\u003csub\u003e2\u003c/sub\u003e/Au detector as a function of illuminated optical power for −1 V and −2 V, respectively. (d) Temporal response of the current.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7048954/v1/a24dad6b20c83a45c6bbb4f9.png"},{"id":88923232,"identity":"5e96b46f-fbc5-42e3-ae52-dfd291b85789","added_by":"auto","created_at":"2025-08-12 18:04:53","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":137859,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Equivalent circuit diagram for synchronous optical modulation and detection. (b) I-V\u003csub\u003ebc \u003c/sub\u003echaracteristics at different modulation voltages U\u003csub\u003eab\u003c/sub\u003e. (c) I-V\u003csub\u003ebc\u003c/sub\u003e characteristics at U\u003csub\u003ebc\u003c/sub\u003e \u0026lt; 0 V. (d) I-V\u003csub\u003ebc\u003c/sub\u003e characteristics at U\u003csub\u003ebc\u003c/sub\u003e \u0026gt; 0 V.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7048954/v1/c4240e2074bb12325f6e28c2.png"},{"id":89908785,"identity":"dfad32c5-a47e-4625-9b89-33627983287f","added_by":"auto","created_at":"2025-08-26 10:29:33","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1041982,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7048954/v1/98f7159d-6e91-45b8-9f2f-9c1d831f94bb.pdf"}],"financialInterests":"There is no conflict of interest","formattedTitle":"Heterogeneously Integrated Micro-ring with SnS₂ for Dual-functional Optical Modulation and Photodetection","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eIn optical neural network systems, input optical power is monitored by a PD in an optical bypass, and the photocurrent is transferred to the modulation voltage of a modulator to form a feedback circuit, finally tuning the transmitted optical power. Such a strategy brings higher power consumption and time delay because of the opto-electric conversion\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. Therefore, with optical modulation and detection in one device, the device footprint is smaller than other on-chip strategies. Research on dual-functional devices based on heterogeneous integration of two-dimensional materials with waveguides delivers lower power consumption, broader bandwidth, and enhanced integration density for optical computing network architectures \u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e,\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e, propelling photonic computing technologies toward high-performance computing and future network systems. This approach not only optimizes current network frameworks but also provides efficient optical solutions for diverse future computing demands. Integrating two-dimensional materials with waveguides enables dual-function devices capable of simultaneous modulation and photodetection, reducing inter-device connections and thereby optimizing optical circuit layout and design \u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. Such highly integrated components diminish photonic network complexity while enabling more flexible and compact optical routing.\u003c/p\u003e\u003cp\u003eThe atomic-scale thickness and exceptional optoelectronic properties of 2D materials facilitate efficient optical modulation and detection under low bias voltages, significantly enhancing system integration density. When incorporated into silicon photonics platform, these materials demonstrate outstanding performance in detectors, modulators, and memristive devices\u003csup\u003e\u003cspan additionalcitationids=\"CR6 CR7\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e. Owing to their high photosensitivity, heterogeneously integrated 2D materials enable broadband photodetection across diverse waveguide platforms through photoconductive, thermoelectric, and plasmonic mechanisms\u003csup\u003e\u003cspan additionalcitationids=\"CR10\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. For modulation functionality, this integration leverages the tunable Fermi levels of 2D materials, capacitive configurations, or thermal effects. Reported materials enabling waveguide-integrated modulation include graphene\u003csup\u003e\u003cspan additionalcitationids=\"CR13\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e, black phosphorus (BP) \u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e,\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e, PtSe\u003csub\u003e2\u003c/sub\u003e \u003csup\u003e17\u003c/sup\u003e, et. al. As widely demonstrated in graphene and TMDCs, an out-of-plane electric field could modify their electronic structures remarkably due to the strong vertical confinements of wave functions\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e. Similarly, BP thin films could be considered as a quantum well, whose band edge allows a reliable electrical engineering to change the optical responses\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e. However, most reported dual-functional devices are graphene-based \u003csup\u003e\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e, which necessitates the use of monolayer graphene and requires the formation of capacitive structures or heterojunctions to achieve modulation functionality. This imposes stringent process requirements on device fabrication.\u003c/p\u003e\u003cp\u003eIn this work, we hybrid integrate SnS\u003csub\u003e2\u003c/sub\u003e onto a micro-ring resonator (MRR) to demonstrate a single device that can simultaneously function as an optical modulator and a photodetector. This device operates without requiring monolayer-specific 2D materials, capacitive heterostructures, or external gating. In this compact device architecture, SnS\u003csub\u003e2\u003c/sub\u003e acts as the primary photoactive material, enabling photon-to-electron conversion for photodetection while simultaneously mitigating light-transmission perturbations induced by Au heating electrodes. Furthermore, the engineered Au electrode design facilitates efficient hot-carrier generation\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e. On one hand, the micro-ring resonator's strong optical confinement enhances light-matter interactions with the 2D material, enabling infrared photodetection through hot-carrier assistance. On the other hand, localized refractive index modulation via the heating electrode delivers optical modulation functionality. The dual-functional device achieves 23 dB modulation depth in the C-band and exhibits sensitive photoresponse with 0.38 A/W responsivity at \u0026minus;\u0026thinsp;2 V. This heterogeneously integrated platform eliminates dependence on monolayer graphene and requires no gate electrodes. Its design flexibility enables deployment as reconfigurable optical elements in on-chip photonic computing systems. Concurrent optical modulation and real-time electrical readout through dual ports permit in-situ monitoring of modulation states, paving the way for ultra-compact integrated photonic circuits.\u003c/p\u003e"},{"header":"2. Results","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Device fabrication and characterization\u003c/h2\u003e\u003cp\u003eConventional approaches for dual-function devices rely on graphene-based capacitors, FETs, or heterojunctions, where an out-of-plane electric field shifts the band edge to enable functionality. These architectures exhibit critical dependence on graphene thickness and require precise capacitor/heterojunction fabrication \u003csup\u003e\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. In contrast, our design eliminates thickness constraints for SnS₂ and operates without external gate bias, significantly reducing process complexity. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(a) illustrates the dual functional device of SnS\u003csub\u003e2\u003c/sub\u003e integrated on a micro-ring resonator. Direct deposition of gold thin films onto the waveguide for thermal modulation induces substantial optical propagation losses, ultimately resulting in the complete quenching of resonant peaks. Therefore, we deploy a two-dimensional (2D) material as an interlayer between the waveguide and the thermally active gold film. This configuration simultaneously attenuates the detrimental influence of the gold heater on the optical transmission characteristics of the micro-ring resonator. Fundamentally, achieving infrared photoresponse in wide-bandgap SnS₂ (E\u003csub\u003eg\u003c/sub\u003e \u0026asymp; 2.07 eV) presents a significant challenge \u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e,\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. Here, we overcome this limitation through hot-carrier-assisted detection enabled by micro-ring-enhanced light-matter interactions. At the same time, the wide-bandgap 2D material SnS\u003csub\u003e2\u003c/sub\u003e exhibits minimal absorption cross-section within the infrared spectrum, implying negligible perturbation to resonant cavity transmission. Crucially, the incorporation of this photoactive material is indispensable for enabling photodetection functionality.\u003c/p\u003e\u003cp\u003eThe SnS\u003csub\u003e2\u003c/sub\u003e was mechanically exfoliated onto the silicon waveguide. Au electrodes (80-nm-thick) were fabricated through lift-off process. All the waveguide structures were fabricated by electron beam lithography (EBL) and inductively coupled plasma (ICP) etching processes. A schematic of the dual-function device architecture is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(a). Electrodes A and B were patterned atop the waveguide and SnS\u003csub\u003e2\u003c/sub\u003e layer for optical modulation, while electrode C\u0026mdash;positioned remotely from the waveguide and modulation electrodes\u0026mdash;contacts SnS\u003csub\u003e2\u003c/sub\u003e exclusively for photodetection. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(b) and Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(d) show the SnS\u003csub\u003e2\u003c/sub\u003e thickness of 18.8 nm measured using atomic force microscopy (AFM). Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(c) shows the Raman spectrum of SnS\u003csub\u003e2\u003c/sub\u003e within the integrated device exhibits characteristic vibrational modes at 315 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. \u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Thermo-optic modulation operation\u003c/h2\u003e\u003cp\u003eIn order to characterize the effect of Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, SnS\u003csub\u003e2\u003c/sub\u003e and Au electrodes deposition on the ring resonator, the transmission spectrum of the ring resonator in each step was measured and shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(a). As can be seen, the transmission spectrum exhibits increased loss after the deposition of the thin gold layer, while the extinction ratio shows no significant change. The extra loss is due to the fact that the gold layer introduces additional absorption. Specifically, the top Au electrode absorbs the evanescent field of the waveguide mode in the telecom band, particularly when a DC voltage is applied between electrode A and electrode B for optical modulation, which generates considerable hot electrons.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eDuring device characterization, we monitored the current variation between heating electrodes A and B under different DC voltages (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec). At 6 V applied bias, the modulation electrodes risk thermal breakdown. To ensure low-power operation and prevent electrode failure, we maintained the loop current below 0.05 A. With DC voltages of 0.5-1 V applied between electrodes A and B, the transmission spectrum evolution is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e (b). We observe a red shift of the resonant notch while the extinction ratio remains statistically unchanged. At the resonant wavelength of 1549.76 nm, the device exhibits an extinction ratio of 24 dB and a 3-dB bandwidth of 0.52 nm, corresponding to a quality factor (Q) of 2980. Under the bias of 0.8 V, a modulation depth of 23 dB is achieved. Increasing the bias from 0 to 0.8 V induces a 1.8 nm red shift, consuming 38 mW electrical power. The thermo-optic tuning efficiency is calculated as 0.047 nm/mW.\u003c/p\u003e\u003cp\u003eWhen a bias voltage is applied between electrodes A and B, hot electrons are generated and tunnel into the conduction band of the SnS₂ layer. These hot electrons collide with intrinsic carriers in SnS₂, but ultimately lose energy via electron-phonon scattering, increasing the lattice temperature. This process is dominated by the thermo-optic effect, inducing a redshift in the transmission spectrum. The resonant wavelength shift (Δλ) relates to the effective refractive index change (Δ\u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eeff\u003c/em\u003e\u003c/sub\u003e) through Eq.\u0026nbsp;(\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e1\u003c/span\u003e):\u003c/p\u003e\n\u003cp\u003e\u003cimg src=\"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAOcAAABZCAYAAADFNDMlAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsMAAA7DAcdvqGQAAA4gSURBVHhe7Z1JiBTXH8ef/4sXg4fxYNyQGR3xIgZNRNC4RccdD+47uBG9iGIUQYyiEBNjzEXB8aAojqIHcUmiibsnwVHw4JKMCu5gDuICgtD/+vx8r62pqe6uqnT3dE//PlBUvarqfrV93+/33vtVvXYpD6MoSsnxPzuvaP7++2/z1VdfmU6dOpkbN27Ytbl59uyZ+e2332zqE6yvqakx7dq1M99884158+aN3WJkmXVsY1qwYIHdoijNqXhxIpbDhw+b8+fPm3379pnr16/bLbk5dOiQ2bFjRzPxweeff26amppMfX29uXnzpojf0aFDB3P8+HEzffp009DQYPbv32+3KEpzKl6ciGXDhg0y79q1q6mtrbVbsoMgf//9d3Pu3Dlz8eJFu7YlVVVVZufOnTb1kdevX5sePXqYiRMn2jWK0hJ1a30cPHjQfPbZZzaVHQQ5c+ZMM2rUKHP06FG79hOIFxFu2rTJXL16VVxdx/Pnz02fPn2kQFCUTKg4LT///LO4m507d7ZrMoPwLl26ZCZMmGDGjRtnTp8+3aKuiiuL0IcNGyZpXGAHrvOAAQNsSlHCUXF6IKw9e/aIFYwCwsPyUbecPXu26dixo9RZ/TgBss+QIUPEBUbUTFjR3r172z0VJZyKFydCmTp1qrifgwYNiuTWnjhxQqwmOPHt2rUr7boGBbhy5Urz6NEjETUTv1GXVslFRYsTEc2bN88sX7483TiTSzRYWRqOEJgD8b169Srd0ktd0y9ARNq9e3dpGFKXVolKRYtzxYoVMl+2bJkIym81qYPSD8ncD1YzKC7E179/fxEfgg8KEJEiYOqm165di+TSUgjQ98ox4EIH+0uVtk/FivPUqVPSinrgwAERDy2ot2/fFgGsX7/e3L171xA89fTp03Rjj3Nbv/jiC5k7nPjo02RfpmDDEmKlbhqllda52rNmzZL00qVLzdChQ6UAUSoIwvcqjcbGxlRtba3MHZ4IU6NGjUpVVVWlpkyZkjp58qSsZ759+3ZZZs4lizJVV1fLf/rh9/48HfX19ZIv28nP/z+sD/uN0vbR2NoQ9u7dK5YOC4kVxE1dvHix3Zpf+H/6V70CQaw1+eBKY2FJM9dghcqk6G4tLltYPGoQWjWTxLvmAxp3njx5IsvMSRcK6qmEAK5evVr6RHGrqZfiAjOn8UmpTIouzkzxqH7YljTeNR+MHDnSXLhwQZaZky4knitrVq1aJQUX9UqESZ2VufaHVi5FFSeiixKPSoNJknjXfIE7+/LlS2kp7dKlS4sGoHzSr18/M2nSJLHQX3/9tRREfpc2V+OR0nYpap2TFlJaRbGKiC7KGxm4e3Pnzi2oQFobCq1ffvlFYnUpiO7duycRS1hTf3+qUlkUzXLyAOaKRw0SJ961nME6/vPPP2bOnDkiTuaEBaowK5uiiTNKPKofhJsr3pUXld1Ly2FTOb3IjBdBAxDuLPO27Cko0SiaW0vsKp3pzhogHIIAmIIWgoYR4lW3bt1q3r59a2bMmKF1L6XiKIrlxArmikd14P7GjXeNQ5iFLbdJqQyKIs4o8aiObPGuQZK4tTgK5T4plUHBxRklHpX6KGSLd6U1M9iARD0t7OF1k36fRylrvIe4oESJR50/f37OeNeGhga7VlEqA42tVZQSpWhdKYqixEPFqSgliopTUUoUFaeilCgqzgTQpcN7pvSl0v1DVw/RT6QJ6leUfKDiTAB9trdu3ZKPbhH5RGjimjVrzPbt29MvaSvKf0XFmRDCDnnXs7Gx0WzcuFFCEwlYL/SL2UrloOJMCOOjtG/f3owfP16imVyUk365QMkXKs4EEJJImOHkyZPTwfy8/sY3j/TtGSVfqDgTQMzvwIEDzfDhwyWNWI8cOWL69u2b8wVyRYmKijMBQSuJWHn9jRelXYA/n1dxb8e0xhcElcKC58RrjQ5a6bnX9+/ft2uM6dWrl11KiETYKnmF4P2xY8dK4L77ULTSduAljLq6OptKpbZt25Z+iaOpqcmuTclycF0cVJwFwL1Nw41h/vr1a7tFKXcQWk1NjU19IpMQM+0fBXVrCwAviDPOCS+L//XXX9pI1IagL3vLli02lZvq6mozZsyYRMEpKs4CQAPRnTt3zLRp0yJ93V4pH3bv3i3tDXHge8R8HD0uKs48Q8MPX7X/6aef5APanourjUFtBNfYgzWMQ7du3cyZM2dsKjoqzjxDEAIhfK6lls+s6Gcu2wYUtMVExZlnqF/yvV2vPi9TcPBdpXwhXLOYqDgVJSK4szU1Nc36MqPw+PFjU1dXZ1PRUXEqSgxoeT127JhNfYSWWEQLzAlQ8HP58mWzcOFCm4qOfuBLUWKA1USAUWXD/giasXDiopZTUWKAa9vQ0BA5NA8hJ+lGAbWcipIAXFe6zHbt2mXXtAQBnz17NnbXi0PFqSglirq1ilKiqDgVpURRcSpKiaLiVJQSRcWpKCWKilNRShQVp6KUKCpORSlRVJyKUqKoOBWlRFFxKkqJouJUlBJFxakoJYqKU1FKFBWnopQoKk5FKVGKKk6+hJ7pC+hs45MOfOuV4dzfvHljtxhZZp37FuyCBQvsltaBYx09erTMM3Hq1KnQc4kKQ9ln+39HWD5cH3etwibGFc11/MD2bF+sz5VPa9+nsocvIRQLRtzKNbBPfX19qqqqSkbq8sNvpk+fLiM8tSaMGFZdXS2DFeWC82WKC//9/fff21Ru/PlwnZYsWZK6d++epIPXnDTnwPWtra1tcZ39BH/rJ2o+SnKKZjkp1Rme4Ny5c+bixYt2bTieOM3OnTtt6iPeTTc9evQwEydOtGuKD5bk119/le/HuBGtM8H5Xrt2zYwcOdKuic7169fNgAEDbCo7wXwY/n7u3Lny5Xl3zceNG5ceTOnLL7+U/+Yr9HzScdmyZaEWNNf9ipqPkpyiiZMbPHPmTOOVrubo0aN2bXO4yYgQlw4B+B8aBqjt06dPq47YtW7dOjN27NicwgTOo2PHjvLwxiWOOIP5IDoGzgEE9OjRo2YFBNvc8bPvjBkz5LyC5LpfcfJRklEUcSK6S5cumQkTJkjpevr06dDBfbjJDJ83bNgwSfN1M0ecBzYKbuTppUuXSr4OjouPAAehoGDck0yWkHPkPxnFmvof5/v+/Xv5b9aRF/VD9iNP0mHDwrkCKdODnSmfsEKLEbg/fPhgOnfubNe0hPPhvPwFYdT75YiSjxKfooiTBxSrxwM3e/ZsKem5oUGcANlvyJAh4irxoDDx8CSxQmEgEtwurE7Xrl3N4MGD00LhGCgggrD+33//DX0AOTYn2ocPH5oDBw6YvXv3yhCAWJhbt26JkMgLr2DNmjUyziMDHgXJVghlyycI14zrx3XMZsE4H86LfB1R7xdEzUeJT1HEeeLECSmFwQmP730GS2u/AFeuXCmuEg8KE7/Ll0v74sULqbvyfxs3bjR//vmn2bFjh1gjQFBB7t69a5eaw3HPmzfP9O3bVwYt4j8RN98qdSLjwWcQnMbGRsmPc8lUH80kzij5+KHgefDgQahww/CfX5T75YibjxKdgosTdwiL4S9VEd6rV6+aldbcZL8AEWn37t2lYSibNUnCokWLRCTOrSVPxPLy5UvJJ8ytzQR1Mx7OH374wa75uA5X050zdbb27dub8ePHS14UNhD0BNzD779Wjij5+HHXNu51i3q/HEnzUXJTcHFSCgdvHA9l//79RXhYBAgKkIeYh4L6DsKJ4tLyYDHqMKLDLfP3/flJ4tbyf2EgPL9LxzFs3rw5bUkQHI1b9C26fXAROU5XEDlo9BoxYoRNNSdXPkGC++fCnV/U++WIm48SnYKK01mCoJvohHfz5k2xItxwHrZgfY6HhPoOD07wQQ5CXlOnTjWzZs2SNBZx6NChIsAgSdxajoUuHgQUhONnosMe15UHmePm3Nh/4MCBZvjw4bIvx3nkyBFxTzlnP+yfrRDKlo8f/pdCLYqryfFxXpxf1PvliJOPkgDb31kQ6Igmi2yT94Cll8M69/mPsI5yF6zgOrv9/xkWxJAP5s+fL/n5IR/yYyJAguP3rLIcH7C//zfsT+e/VxjYNR/xCpGUZwlDO/whVz7AbwkE8F+LTEEEDo6N83LL/t+GTeybJJ+2yJUrV1LffvutLG/bti19LVh21NTU2KX4FDVCKF/woK5atSrl1Q2biQCRunkhcIIohPBbA87Hc/1bFIhKbigg6+rqZBmROkGyjEBdJFtTU5OkmcelLMVJ6c0JIxTCxyixCe1DrMwLKR5n+cpdoAgST0VD7OKD0PwWEUH6wZo6iwrB/aNSlK6UQuA9VMaznlJP8sQpdS/qrMyjNB4lhfoYraTfffdduo5WbnDcXgEnDVWtGQ5ZrnjemdmyZYtNGWkQ89OzZ0+79BG6uxhANyzoJBtlKc5+/fqZSZMmSSc+YWK0sNJoRF9dlMaj/wotkzQilWsLZbkff2uze/duaW3PBAEiBG/44TmNO4huWYqT8DWs5bt376T1EKHSVUHIWfCiKEo+YRh5wBqGwXamoDXt1q2bOXPmjE1Fo2zdWqwj4+zPmTPHeHVAmSNMtQZKIfHq6nYpHFzeP/74w6b+GzqytaLEAKvIRwHCZLN8+XIxEEGrCdTv6XePI7eytZyK0hrgziJO5946fvzxR6lXOmHS+OPf5/Hjx6aurs6moqHiVJSY0PJ67NgxmzLyju/atWslOo3QUSYaf/z1UuK1Fy5caFPRULdWUWKSzbUNg/0RNG0kcVDLqSgxwSI2NDSYXr162TXZQchxu1FALaeiJIRGHr7WwbuumUDAZ8+ezdj1kg0Vp6KUJMb8HxHCdKaws38UAAAAAElFTkSuQmCC\" width=\"231\" height=\"89\"\u003e\u003c/p\u003e\n\u003cp\u003eWhere \u003cem\u003en\u003c/em\u003e\u003csub\u003e\u003cem\u003eg\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003eλ\u003c/em\u003e\u003csub\u003e\u003cem\u003e0\u003c/em\u003e\u003c/sub\u003e are real part of the group index and resonant wavelength, respectively. Δ\u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eeff\u003c/em\u003e\u003c/sub\u003e exhibits a linear dependence on waveguide temperature, inducing a thermo-optic redshift in the transmission spectrum upon heating.\u003c/p\u003e\u003cp\u003eThe corresponding resonant wavelength shifting vs power is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(d). Given the linear relationship between temperature and power (T\u0026prop;P), Equations (\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) and (\u003cspan refid=\"Equ2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) collectively demonstrate that the resonant wavelength shift scales proportionally with applied power (Δλ\u0026prop;P). Then, we measured the the dynamic response of the modulator (shown as in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee). The rise time (from 10\u0026ndash;90%) was 3.4 \u0026micro;s and the decay time (from 90\u0026ndash;10%) was 6.9 \u0026micro;s. The rise time was decided by the heating speed powered by the DC voltage applied across the thermal electrodes, whereas the decay time by the cooling speed.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Hot-carrier-assisted photodetection operation\u003c/h2\u003e\u003cp\u003eUnder non-modulated conditions (U\u003csub\u003eab\u003c/sub\u003e=0 V), we measured the current (I\u003csub\u003ebc\u003c/sub\u003e) between electrode B and electrode C as a function of bias voltage. By coupling light at a wavelength of 1549.7 nm into the waveguide, photocurrents are observed, as the I-V curves shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(a), which are obtained at different incident optical powers. When light is coupled into the waveguide toward the Au/SnS\u003csub\u003e2\u003c/sub\u003e interface, the rectifying I-V characteristics demonstrate asymmetric behavior about zero bias, confirming back-to-back Schottky barrier formation. Band engineering analysis reveals that this photoresponse originates from the interfacial energy band alignment depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(b). The work function of Au at equilibrium ensures Fermi-level alignment with the n-type SnS\u003csub\u003e2\u003c/sub\u003e (i). The energy band diagrams of the device under U\u003csub\u003ebc\u003c/sub\u003e \u0026gt;0 V (ii) and U\u003csub\u003ebc\u003c/sub\u003e \u0026lt; 0 V (iii) reveal the physical origin of the I-V characteristics. Waveguide evanescent field excitation at the metal electrode generates non-equilibrium hot electrons. At zero bias, the built-in electric field of the Au/SnS\u003csub\u003e2\u003c/sub\u003e Schottky junction enables hot electron injection into SnS\u003csub\u003e2\u003c/sub\u003e, with subsequent diffusion-driven transport to electrode C. Under U\u003csub\u003ebc\u003c/sub\u003e \u0026gt;0 V, the applied electric field drives directional drift of these carriers from electrode B through the SnS2 channel to electrode C. Conversely, U\u003csub\u003ebc\u003c/sub\u003e \u0026lt; 0 V establishes a reverse field that blocks hot electron injection from electrode B into SnS\u003csub\u003e2\u003c/sub\u003e. Besides, due to the exitance of the micro-ring resonator, the interaction between light and SnS\u003csub\u003e2\u003c/sub\u003e is enhanced since the light penetrates multiple times and interacts with SnS\u003csub\u003e2\u003c/sub\u003e, and the thermal carriers generated by lattice vibrations, eventually generate current under bias voltage. Experimental results show that the SnS\u003csub\u003e2\u003c/sub\u003e device exhibits a dark current of 41.7 nA at \u0026minus;\u0026thinsp;2 V bias. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(c), when a 1550 nm light source with 0.1 \u0026micro;W optical power is coupled into the waveguide through the grating, the device demonstrates a photoresponsivity of 0.38 A/W under \u0026minus;\u0026thinsp;2 V bias. Notably, the responsivity increases with the applied bias voltage. In Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(d), the measured 10\u0026ndash;90% rise time and 90\u0026ndash;10% fall time are 8.4 ms and 11.8 ms, respectively.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4. Mechanism of synergistic current dynamics in dual-mode operation\u003c/h2\u003e\u003cp\u003eAdditionally, under modulated conditions with DC bias applied between electrode A and electrode B, the output current between electrode B and electrode C was measured while coupling 1549.7 nm laser light into the waveguide. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(a) shows the equivalent circuit for synchronous optical modulation and detection. The corresponding results are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(b). These results indicate that applying different voltages between electrodes A and B affects the output current between electrodes B and C. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(c) shows that increasing U\u003csub\u003eab\u003c/sub\u003e enhances output current I when U\u003csub\u003ebc\u003c/sub\u003e \u0026lt; 0 V. Conversely, increasing U\u003csub\u003eab\u003c/sub\u003e reduces output current I when U\u003csub\u003ebc\u003c/sub\u003e \u0026gt;0 V (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(d)). This phenomenon arises from the superposition of currents under bias. When U\u003csub\u003ebc\u003c/sub\u003e\u0026lt;0 V (defined as current flowing from electrode C to electrode B), U\u003csub\u003eab\u003c/sub\u003e induces local heating at the Au electrode, generating hot electrons. The resulting thermal gradient drives a diffusion current (I\u003csub\u003ediff\u003c/sub\u003e) in the same direction (electrode C to electrode B). The total current is given by: I\u0026thinsp;=\u0026thinsp;I\u003csub\u003ediff\u003c/sub\u003e+I\u003csub\u003ebc\u003c/sub\u003e, where I\u003csub\u003ebc\u003c/sub\u003e is the baseline current at U\u003csub\u003eab\u003c/sub\u003e = 0 V (note: denotes the current flow direction). As U\u003csub\u003eab\u003c/sub\u003e increases, I\u003csub\u003ediff\u003c/sub\u003e increases, leading to an enhancement of the total current I under negative U\u003csub\u003ebc\u003c/sub\u003e. Conversely, when U\u003csub\u003ebc\u003c/sub\u003e \u0026gt;0 V, the total current becomes: I\u0026thinsp;=\u0026thinsp;I\u003csub\u003ebc\u003c/sub\u003e\u0026minus;I\u003csub\u003ediff\u003c/sub\u003e. Here, an increase in U\u003csub\u003eab\u003c/sub\u003e enhances I\u003csub\u003ediff\u003c/sub\u003e, but since I\u003csub\u003ediff\u003c/sub\u003e flows opposite to I\u003csub\u003ebc\u003c/sub\u003e, the net current I decreases.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThis dual-functional device uniquely integrates optical modulation and real-time photocurrent readout through its dual-port electrode design\u0026mdash;a paradigm distinct from conventional approaches. Crucially, the output current at the detection port (Electrodes B/C) provides in situ monitoring of the modulation state. By establishing the correlation between modulation voltage (Electrodes A/B) and output current, we demonstrate a voltage-to-current feedback mechanism. When deployed in on-chip optical computing systems, this enables real-time crosstalk monitoring between devices, thereby enhancing computational accuracy through dynamic feedback control. It should be noted that our device is not designed for high-frequency operation, which would need further optimization of electrical contacts on the device in order to reduce the associated resistive‐capacitive \u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e time constant of the RC circuit. Reducing the contact resistance as well as capacitance allows the devices to work over GHz.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Discussion","content":"\u003cp\u003eIn summary, we demonstrate a compact SnS₂-based dual-functional device integrated with a micro-ring resonator that simultaneously achieves optical modulation and photodetection through strategic electrode design, eliminating the need for conventional gate-voltage control or heterojunction structures and thereby significantly simplifying fabrication. The device achieves 23 dB modulation depth and exhibits hot-carrier-assisted infrared photodetection with the responsivity of 0.38 A/W at \u0026minus;\u0026thinsp;2 V bias. This design paradigm, applicable to diverse 2D materials, extends their silicon photonics utility while addressing next-generation computing needs. It enables real-time modulation-state monitoring via photocurrent readout (Electrodes B/C) and enhances system stability through feedback-driven crosstalk suppression\u0026mdash;establishing a scalable pathway to robust multifunctional photonic integrated circuits.\u003c/p\u003e"},{"header":"4. Materials and methods","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e4.1 Waveguide fabrication\u003c/h2\u003e\u003cp\u003eThe bottom layer includes a ring resonator with grating couplers on a silicon-on-insulator (SOI) platform with 220 nm device layer, the height of the ridge waveguide 70 nm, and the slab of 150 nm. Both the straight and ring waveguide have a width of 450 nm and the gap between them is 100 nm. A pair of tapered gratings was designed at both ends of the straight waveguide for efficient coupling for TE mode. All these structures were fabricated by electron beam lithography (EBL) and inductively coupled plasma (ICP) etching processes. Then, the 10 nm thick aluminum oxide (Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e) dielectric layer between the SOI platform and the SnS\u003csub\u003e2\u003c/sub\u003e is deposited by atomic layer deposition (ALD) which acts as an electrical isolation layer. After this, another step of e-beam lithography isdone to define the metal electrodes. The electrodes are made by evaporating 80 nm of Au using an evaporator and lift-off process.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e4.2 TMDC fabrication\u003c/h2\u003e\u003cp\u003eBulk flakes of SnS\u003csub\u003e2\u003c/sub\u003e (Shenzhen Six Carbon Technology Co., Ltd.) are exfoliated via the Scotch tape method onto polydimethylsiloxane (PDMS). Next, the target flakes are found using an optical microscope and transferred to the intended waveguide by dry transfer technique.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e4.3 Device measurements\u003c/h2\u003e\u003cp\u003eDevice characterization was performed on an edge-coupling platform with polarization-maintaining fibers. Tunable laser light (1520\u0026ndash;1620 nm) was coupled into the waveguide via a high-precision alignment stage. Thermo-optic modulation was driven by a programmable DC source (Keysight B2912A) providing bias voltages to Electrodes A/B. Temporal response of the modulation function was captured using a waveform generator and a real-time oscilloscope (Lecroy, 740Zi-A). Photodetection metrics including I-V characteristics and response time were quantified using a semiconductor parameter analyzer (Keysight B1500A) under tunable laser (TUNICS T100S-HP).\u003c/p\u003e\u003c/div\u003e"},{"header":"Declarations","content":"\u003ch2\u003eConflict of interest\u003c/h2\u003e\u003cp\u003eThe authors have no conflicts to disclose.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThis research was funded by the National Natural Science Foundation of China (62205029); the National Key Research and Development Sub project (2022YFF0705801); the Young Elite Scientists Sponsorship Program by CAST (2022QNRC001).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eZhong, C.\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e Graphene/silicon heterojunction for reconfigurable phase-relevant activation function in coherent optical neural networks. \u003cem\u003eNature Communications\u003c/em\u003e \u003cstrong\u003e14\u003c/strong\u003e, 6939, doi:10.1038/s41467-023-42116-6 (2023).\u003c/li\u003e\n \u003cli\u003eWu, J.\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e Dual-function optical modulation and detection in microring resonators integrated graphene/MoTe2 heterojunction. \u003cem\u003eApplied Physics Reviews\u003c/em\u003e \u003cstrong\u003e11\u003c/strong\u003e, doi:10.1063/5.0207874 (2024).\u003c/li\u003e\n \u003cli\u003eYoungblood, N., Anugrah, Y., Ma, R., Koester, S. 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Fundamental Optical Absorption in SnS\u003csub\u003e2\u0026nbsp;\u003c/sub\u003eand SnSe\u003csub\u003e2\u003c/sub\u003e. \u003cem\u003ePhysical Review\u003c/em\u003e \u003cstrong\u003e143\u003c/strong\u003e, 536-541, doi:10.1103/PhysRev.143.536 (1966).\u003c/li\u003e\n \u003cli\u003eLiu, Z.\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e High Photoresponsivity and Response Speed of Visible-Light Photodetectors Based on Tin Disulfide/Indium-Doped Tin Disulfide Homostructures. \u003cstrong\u003e11\u003c/strong\u003e, 2202087, doi:https://doi.org/10.1002/adom.202202087 (2023).\u003c/li\u003e\n \u003cli\u003eHu, Y.\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e Controlled growth and photoconductive properties of hexagonal SnS2 nanoflakes with mesa-shaped atomic steps. \u003cem\u003eNano Research\u003c/em\u003e \u003cstrong\u003e10\u003c/strong\u003e, 1434-1447, doi:10.1007/s12274-017-1525-3 (2017).\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-7048954/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7048954/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eDual-functional devices capable of simultaneous modulation and photodetection offer enhanced flexibility for on-chip photonic integrated systems. However, fabricating such dual-functional devices remains challenging due to process compatibility issues, device instability, and insufficient light-matter interaction enhancement. As two-dimensional materials exhibit unique advantages in on-chip heterogeneously integrated photonic devices, particularly modulators and photodetectors, we demonstrate a dual-functional few-layer SnS\u003csub\u003e2\u003c/sub\u003e integrated above a silicon-on-insulator (SOI) micro-ring resonator. By the electrode-engineered design, we achieve simultaneous light modulation and detection without external gate control or heterojunctions, which significantly simplifies fabrication procedures. The device achieves modulation depth of 23 dB and exhibits hot-carrier-assisted infrared photodetection with the responsivity of 0.38 A/W at a bias voltage of \u0026minus;\u0026thinsp;2 V. This integrated architecture can not only reduce the footprints of photonic integrated circuits but also facilitate the real-time monitoring of modulation states via electrical feedback, thereby enhancing operation stability of the on-chip photonic computing systems.\u003c/p\u003e","manuscriptTitle":"Heterogeneously Integrated Micro-ring with SnS₂ for Dual-functional Optical Modulation and Photodetection","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-12 17:56:48","doi":"10.21203/rs.3.rs-7048954/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"178bfcc1-9f80-4a3a-9edc-0672f613b6d2","owner":[],"postedDate":"August 12th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":52794070,"name":"Physical sciences/Optics and photonics/Optical materials and structures/Silicon photonics"},{"id":52794071,"name":"Physical sciences/Optics and photonics/Applied optics/Optoelectronic devices and components"},{"id":52794072,"name":"Physical sciences/Optics and photonics/Applied optics/Integrated optics"}],"tags":[],"updatedAt":"2025-08-26T10:21:26+00:00","versionOfRecord":[],"versionCreatedAt":"2025-08-12 17:56:48","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7048954","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7048954","identity":"rs-7048954","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}