Au Coated Photonic Crystal Fiber based Surface Plasmon Resonance Sensor: Design and Investigation

Au Coated Photonic Crystal Fiber based Surface Plasmon Resonance Sensor: Design and Investigation | 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 Research Article Au Coated Photonic Crystal Fiber based Surface Plasmon Resonance Sensor: Design and Investigation Sadia Afrin, Sanchita Sarker, Bikash Kumar Paul, Md Abir Hossain, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3998814/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 We propose in this research an idiosyncratic, shallow to erect, and highly perceiving Plasmonic material-coated photonic crystal fiber (PCF) based micro-structured biosensor. Our precedence has a cardinal pattern of circular air holes inside the fiber, which leads to a superior sensing performance. The evaluation of all the sensor characteristics has been expelled by sustaining the finite element method (FEM) of COMSOL Multiphysics. The gold (Au) layer just around the fiber acts as the plasmonic material. Gold is picked out due to its high stable rate and maximum resonance peak value in the sensing environment. After the swelling of all the fiber parameters, we derived a maximum amplitude sensitivity (AS) and wavelength sensitivity (WS) of 114 RIU − 1 and 20000 nm/RIU, respectively, with a maximum sensor resolution of 1.15×10 − 9 for wavelength. The overall analyte sensing range is from refractive indices 1.36 to 1.4. With its enhanced performance in terms of sensitivity, we believe that this Plasmonic material-coated PCF biosensor can potentially contribute to the detection of unknown analytes. Surface Plasmon Resonance Plasmonic Biosensor Sensitivity Photonic crystal fiber Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Introduction The silica crystal lattice is extremely transparent and has certain distinctive visual traits. Leveraging these peculiar characteristics, an optical fiber is made. Many engineers and scientists have recently put forward their exceptionally qualified studies toward optical fiber technology and photonic crystal fiber (PCF) technology. PCF is a sort of optical fiber used in modern technology that offers greater stability than standard or traditional optical fiber. It is assembled using a synthetic array of air-filled holes running the length of the fiber. PCF has lingering optical characteristics, including perpetually single-mode operating [ 1 ], an enormous effective area, ultra-flat dispersion, high nonlinearity, and exceptionally high birefringence, which have all been documented in prior literature [ 2 ]. The size or form of the PCF, the hosting material, the light propagation mechanism, and the operating wavelength mentioned in [ 3 ] all have a significant impact on these important features; below is a report on them. The two kinds of light that propagate through the PCF are photonic band gap (PBG) and index guiding (IG). In the case of IG-PCF, light is steered through the fiber core because it has a higher refractive index than the surrounding cladding region. Total internal reflection (TIR) of light has taken place here. On the other hand, it has been stated in [ 4 – 6 ] that PBG-PCF light can be propagated through the fiber core via the photonic band gap effect. PBG-PCF has a shorter transmission band than IG-PCF of these two types of fiber [ 4 ]. The core of conventional optical fibers was consistently infused with high-index material after initially being manufactured from pure silica [ 7 ]. Numerous substances have recently been created as the foundation for PCF. Due to their new optical features described in [ 9 ], tellurite, graphene, and chalcogenide glass with polymer are extensively utilized over an expanded infrared transmission band. PCF fields of application are steadily broadening. It ushered in a new era of swift interaction in the area of telecommunication. The core of the internet is optical fiber. PCF is employed in a variety of fields besides the telecom industry, covering sensing (chemical, gas pressure, and temperature), biological diagnostics, spectroscopy, optical coherence tomography (OCT), high power technology, supercontinuum generation, optical switching, optical amplification, and more [8–11]. Recently, PCF has caught an extensive amount of attention as a result of diagnostic testing that may identify proteins, germs, and glucose in test samples [ 12 – 16 ]. By depicting the brain system, neuroscience is currently experiencing incredible advancement [ 17 ]. PCF has spearheaded a pioneering and unrelenting pursuit of research globally. In the fields of connectivity, along with sensing, microscopy, metrology, astronomical spectroscopy, and numerous other areas, it is only getting started. Sensing is one of the potential applications among these many different fields. A surface plasmon resonance (SPR) sensor based on PCF has recently started vibrating. SPR is a robust, label-free measuring method used to find binding kinetics, chemical affinities, and interactions. It runs on applied light. Polarities are generated as an outcome of the mutual interaction of surface-bound light plasmons. Surface plasmon resonance (SPR), plasmon waveguide resonance (PWR), and plasmon imaging (SPR-I), as well as several other methods, are based on this phenomenon. The communication infrastructure that is included has become more reliant on optical fiber in recent times. Optical fiber is a noteworthy advancement in technology that revolutionized the paradigm of telecommunications. Because of its anonymous performance, which involves signal transmission across farther distances at higher data rates, with little data loss, it gets used in place of copper wire and satellite links [ 1 ]. In non-telecom sectors that might involve medical imaging, remote sensing, machining, illumination, and so on, optical fiber is also used [ 2 – 3 ]. On average, an optical fiber is a waveguide with a cylindrical shape constructed of two glasses that redirect light signals down its axis. One is a solid glass core featuring a higher refractive index that runs down towards the center of the fiber,the core's inherent light [ 6 ]. The concept of "conventional optical fiber" alludes to this sort of optical fiber. Optical fiber has multiple widespread applications in the two distinct telecom and non-telecom sectors, but it additionally comes with several limitations. These constraints are mainly imposed by an assortment of elements, notably the traits of the glass utilized to make it [ 7 ], the rigidity of silica glass, and others. A new technique called photonic crystal fiber (PCF) has been developed to get around this restriction. It is sometimes referred to as the holey optical fiber (HOF) or the microstructure optical fiber (MOF) [8]. Eli Yablonovitch and Sajeev John from Bell Communications Research and the University of Toronto both made predictions about the photonic band gap (PBG) in 1987. PBG has emerged as one of the hottest topics in optical technology in the 1990s. The idea was to construct the proper structures to prevent photons with energy levels, or wavelengths, matching PBGs, from passing freely through a fixed wavelength. By drilling holes with a diameter of 1 mm in a block of material with a refractive index of 3.6, Yablonovitch and his associates developed PBG material for the first time in 1991. This structure had a bandgap in the microwave area because the bandgap wavelength is on the order of the distance between the air holes in the photonic crystal. During the CLEO/QELS meeting in 1991, Philip Russell, who was intrigued by Yablonovitch's findings, had a huge "crazy" notion for "something different" [ 9 ]. By forming a two-dimensional photonic crystal in the cladding that is a periodic wavelength-scale lattice of small air holes in the glass, Russell proposed that light might be captured inside a hollow fiber core. When constructed properly, the photonic crystal cladding that runs the length of the fiber can stop light from escaping from the hollow core. Since they rely on the peculiar characteristics of photonic crystals, these new fibers are referred to as PCFs. In this sort of micro structured optical fiber, the cladding around the cable's core must be shaped using photonic crystals. Surface plasmon resonance (SPR)--based PCF sensors have gained popularity among academics in recent years due to their distinctive characteristics and wide range of practical applications. Due to their high sensitivity, SPR sensors are frequently used in a variety of applications, including water testing [10], maintaining food quality, bio-sensing, medical diagnostics, gas detection, bio-imaging, environment monitoring, real-time monitoring, organic chemical sensing, glucose monitoring, disease detection, and more [11–15]. Applications based on optical sensors [ 16 – 22 ], terahertz sensors [ 23 ], and SPR sensors [11–15] are being updated quickly to keep up with the development of contemporary technology, Ritchie et al. made the first observation regarding SPR using a theoretical approach in the 1950s [ 25 ]. Liedberg et al. first discussed SPR in 1983 based on prism coupling [ 26 ]. The prism is typically used to activate surface modules. There are some drawbacks to using prism-based SPR sensing devices, such as their hefty size and assortment of optical and mechanical components. Additionally, it is inappropriate for remote sensing applications [ 27 ]. The first optical fiber-based SPR sensor was proposed by R.C. Jorgenson in 1993. To expose the plasmon response, the fiber core was coated with gold film. By using optical fiber for prisms, the aforementioned restriction can be bypassed. To lower the technical cost and the size of sensor devices, SPR-based sensors are required. Because of its many appealing properties, such as controllable birefringence, high confinement, and single mode propagation, PCF is also beneficial [ 14 – 15 , 25 – 28 ]. These features allow for simple manipulation of an evanescent field. Effective, sensitive performance is managed by the evanescent field the PCF-based sensors offer a stunning design as well. In addition, SPR sensors offer higher sensitivity than fiber-based sensors. Additionally, it has a lower peak resistance than fiber-based sensors [ 29 , 30 ]. In this paper, we suggest a straightforward spiral PCF structure-based SPR sensor in this study to achieve high sensitivity and low loss properties. This study aims to investigate the performance parameters numerically. By changing a number of the sensor's structural properties, we primarily concentrate on the sensitivity analysis. The numerical analysis is carried out in the extended refractive index (RI) sensing range of 1.36 to 1.4 in both x- and y-polarized modes. Since the plasmonic material is placed on the PCF's outermost layer, it reduces the major fabrication challenges to get the best sensing performance, the impact of altering fiber design factors such as pitch, air hole diameter, and gold layer thickness is examined. An in-depth discussion is also given on potential fabrication methods for the suggested PCF and thin outer gold layer. The geometry of the proposed sensor A sensor's construction has a significant impact on its performance. The structural design, i.e., where the air holes are located inside the core, establishes the guiding properties of the sensors and controls their performance. The external sensing-based SPR sensor in this instance uses a hexagonal lattice-based PCF structure with circular air holes and a gold coating. A perfectly matched layer (PML), which reduces undesired nonphysical radiation, is also included to assess the sensor's effectiveness. Double-layer square air holes with circles make up the suggested sensor. Using COMSOL Multiphysics technologies that are readily available on the market, the finite element method (FEM) is used to analyze numerically how well sensor’s function. Using the amplitude integration method and the wavelength integration method, respectively, the maximum gain amplitude sensitivity of this elevated structure is 114 RIU and the wavelength sensitivity is 10000 nm/RIU. Applications for the suggested sensor in biophotonics are numerous. Figure 1 (a) delineates the 2D cross-section of our proffered sensor. The interspace between the centers of two adjacent air cavities is defined as pitch and is symbolized by p. Two different diameters (d 1 and d c ) of air holes are utilized for their advantageous behavior. In the cladding region, two hexagonal-shaped clusters, each consisting of ten circular-shaped air holes with a bore of (d 1 ), are put down opposite each other along the horizontal axis. Besides, two air holes with the same diameter (d 1 ) create two v-shaped arrangements deposited along the vertical axis as mirror reflections. The prudent disposition of the air holes, having a ( d 1 ) diameter, assists in forming four channels for the propagation of light from the core to the plasmonic mode. The scaled-down corner air holes with a diameter of (d 1) are employed to limit the confinement loss since these air holes avert light scattering from the focal point of the sensor. The numerical value of these air hole diameters ( d c = 0.4 µm) has also been selected by the previously mentioned works. The constituent of the fiber is determined to be fused silica (SiO 2 ). There are several metals, such as copper (Cu), gold (Au), and silver (Ag), that are utilized as plasmonic materials. Among them, gold shows chemically stable behavior in an aqueous environment and responds with a higher resonance peak. A thin gold layer is employed to encompass the cladding section, and the film thickness is denoted as t g . Since the analyte layer thickness ( t a ) is less significant in terms of sensing performance, an arbitrary thickness of 5 µm is decided for this layer. Here, an artificial perfectly matched layer (PML) with a thickness of t PML =1.5 µm is utilized at the outer portion of the computational area to absorb the scattered evanescent field. In a practical sensor, the PML layer is absent, as it is employed only for better simulation purposes. After optimization, regular air hole diameter, pitch, and gold layer thicknesses were found to d 1 = 0.8 µm, p = 2.0 µm, and t g =30 nm respectively. The schematic experimental setup of the proposed plasmonic biosensor has been demonstrated in Fig. 1 (b). The evanescent field should be directed suitably towards the metal layer so that it may easily interface with the metal layer electrons to provide improved sensing performance. Figures 2 (a) and 2(b) show tight confinement of light, a sign of low CL. Figures 2 (c) and 3(d) make it clear that our proposed sensor exhibits outstanding guiding properties as a result of the strategic arrangement of air holes. A strong core mode-SPP mode coupling is created by the proper interaction of the evanescent field and metal layer. Note that in this context, the terms "x-polarization" (x-pol) and "y-polarization" (y-pol) refer to the sensor's response to the incidence of, respectively, x-polarized light and y-polarized light. When we positioned the wavelength at 0.8 µm and the concentration of the analyte at 1.36, we obtained SPP mode. Numerical Analysis For theoretical investigations of different types of PCF properties, numerical analysis is a crucial component. It bases its analysis mostly on the fact that electromagnetic waves are complicated. To investigate and comprehend the propagation of the electromagnetic fields in the photonic crystals, computational methods were created using electromagnetic wave symmetries and periodicities. [ 30 ] In this section, we'll go over the techniques used to calculate the refractive index, confinement loss, sensor resolution, amplitude sensitivity, and wavelength sensitivity of PCFs. Numerous numerical techniques are well known for studying optical phenomena, including finite difference time domain (FDTD), partial wave expansion (PWE), effective mode index (EMI), and full vector-finite element method (FV-FEM). Electromagnetism has been subjected to the FEM. When there is a partial differential equation (PDE) with boundary conditions, the FEM is used in both the physical and engineering sciences. It can be created using different weighted residual methods. Analytical techniques for diverse structures and issues cannot be used to solve these PDEs. These approximations are calculated using the FEM. The finite element method's basic idea is to divide the computation domain into discrete, or finite, subdomains, known as finite elements, and then use straightforward functions, such as linear and quadratic functions, to roughly approximate the unknown solution over each element. All of the PCF's properties listed here are analyzed using COMSOL Multiphysics version 5.5a. Numerical analysis is performed using the Finite Element Method (FEM) and MATLAB version 2016. In optics, a material's index of refraction, often known as its refractive index, is a dimensionless quantity that characterizes how light moves through that medium. Fused silica serves as the background material in this suggested sensor. It is possible to determine the refractive index of fused silica using Sellmeier's equation no (i) in ref [ 33 ]. $$\text{n}\left(\lambda \right)=\sqrt{1+\frac{{B}_{1}{\lambda }^{2}}{{\lambda }^{2}-{C}_{1}}+\frac{{B}_{2}{\lambda }^{2}}{{\lambda }^{2}-{C}_{2}}+\frac{{B}_{3}{\lambda }^{2}}{{\lambda }^{2}-{C}_{3}}} \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \left(\text{i}\right)$$ Where n is refractive index of fused silica that depends on wavelength and λ is the wavelength in µm. B 1 , B 2 , B 3 , C 1 , C 2 , C 3 ara the Sellmeir Constants for the background material silica. The values of constants are respectively 0.69616300, 0.407942600, 0.897479400, 4.6791E − 15 µm 2 , 1.3512E − 14 µm 2 and 9.7934E − 11 µm 2 for fused silica. Various types of loss could happen when light is propagating. Loss due to confinement is one of them. Confinement loss happens when a mode is forced into a tiny area, which causes the mode to partially propagate outside of the fiber (outside of the fiber's core). The following equation (ii) can be used to get the parameters of the sensor's performance evaluation of the confinement loss in ref [ 35 ]: α = 8.686 × k0 × Im[n eff ] × 10 4 dB/cm ……………………………………………..(ii) Where, the number of free space is denoted by k 0 = 2π/λ operating wavelength is denoted by lambda and the imaginary part of the effective refractive index denoted by Im neff The effectiveness of a PCF-based SPR sensor is evaluated using sensitivity. To calculate the sensitivity, we used the formula shown in equation (iii) in ref [ 36 ]. \({S}_{\lambda }\left(\frac{nm}{RIU}\right)=\frac{\varDelta {\lambda }_{peak}}{{\Delta }{n}_{a}}\) …………………………………………………………………..(iii) When \(\varDelta {\lambda }_{peak}\) is used to indicate the distinction of wavelength peak shifts and \({\Delta }{n}_{a}\) is used to indicate the differenciation of analyte refractive index RI.. A short change of analyte RI is possible to accurately detect by using the performance of sensor resolution. Using the following equation (iv) in ref [ 37 ] we obtain the resolution of the raised structure: R(RIU)= \(\left(\frac{{\Delta }{n}_{a}\times \varDelta {\lambda }_{min}}{\varDelta {\lambda }_{peak}}\right)\) ……………………………………………………….……..(iv) Where \({\Delta }{n}_{a}=0.01\) , \(\varDelta {\lambda }_{min}=0.1 nm and\) \(\varDelta {\lambda }_{peak}=maximum\) value of peak λ differences. The sensitivity is measured using either the phase detection method or the wavelength interrogation method. Although these technologies are economical, they offer a difficult process to test sensitivity. The amplitude interrogation approach, which measures the amplitude sensitivity at a set wavelength, can, however, be used to solve this issue. It is possible to determine the amplitude sensitivity using the following equation no (v) in ref [ 38 ]: \({S}_{A}\left(\lambda \right)\left[RI{U}^{-1}\right]=-\frac{1}{\alpha (\lambda ,{n}_{a})}\frac{\delta \alpha (\lambda ,{n}_{a})}{\delta {n}_{a}}\) ………………………………………….…..(v) Here, \(\left(\lambda ,{n}_{a}\right)\) indicates the overall propagation loss at a specific refractive index RI of analyte and \(\left(\lambda ,{n}_{a}\right)\) indicates the difference between the two loss spectra. Result Analysis The section describes the numerical analysis of propagation characteristics in fundamental mode. In order to procure an enhanced sensing performance, the evanescent field should be maneuvered appropriately towards the metal layer so that it can easily interface with the metal layer electrons. The EM field dispersal of our lodged sensor for both x- and y-polarization modes. Tight confinement of light, which indicates low CL, can be realized from Fig. 2 (a) and 2 (b). It is evident from Fig. 2 (c) and 2 (d) that our suggested sensor manifests excellent guiding property due to the judicious placement of air holes. Appropriate evanescent field-metal layer interaction forms a robust core mode-SPP mode linkage. Note that, here x-polarization (x-pol) and y-polarization (y-pol) mode refers to the response of the sensor due to the incidence of x-polarized light and y-polarized light, respectively. Figure 3 and Fig. 4 shows the confinement loss sensor dependent on wavelength with different gold layer thickness t g are 20, 25, 30 nm and analyte n = 1.36 and n = 1.37, for the thickness variation of gold layer. The variation process has been executed in a brute force manner At 1.36, when gold thickness is 20 nm the loss becomes lower compare to thickness 30 nm. Figure 5 and Fig. 6 shows the maximum amplitude sensitivity at thickness t g =20 nm compared to thickness 25 nm and 30 nm. For this reason, we use the thickness 30 nm in our proposed sensor. The amplitude sensitivities of 45, 55, and 63 RIU − 1 are attained for the t g of 20 nm, 25 nm, and 30nm, respectively. Figure 7 and Fig. 8 represents the confinement loss of proposed sensor dependent on wavelength with different pitch of circle. It has seen from the loss curves in Fig. 6 . that when the pitch of the circle increases the loss curve decreases a little. For analyte n = 1.37 when the pitch is 1.9 µm the peak loss shows 230 dB/cm, for 2 µm the peak loss shows 331 dB/cm and for 1.95 µm the peak loss shows 304 dB/cm . Figure 9 and Fig. 10 shows the amplitude sensitivity differences among pitches where pitch 1.9 µm gave more sensitivity than 1.95 µm and 2 µm gave highest sensitivity than both 1.9 and 1.95 µm for analyte 1.36 and 1.37. For this reason we use pitch 2 µm in our proposed sensor. Figure 11 and Fig. 12 depicts the variation in Confinement Loss and Resonance Wavelength due to the change in analyte for x- polarization and y- polarization modes. We conducted the sensors performance analysis in the RI range 1.36–1.4 with an interval of 0.01. The sensor exhibited the peak WS of 114 nm/RIU and 1000 nm/RIU for x-pol and y-pol, respectively which are comparatively high compared to the most other existing SPR based sensors. Figure. 12 and Figure 13 render information regarding the adaptation of Amplitude sensitivity to the modification of RI for x- pol and y-pol. It is undeniable that the AS is proportionate to RI, and with the increase of RI, AS also improves. However, at analyte RI of 1.40 the CL peak curtails along with a broadening of the peak, which effectuates an intense truncation in AS. Regardless of that a max AS of 114 RIU -1 (x-pol) and 105 RIU -1 (y-pol) is achieved at an analyte RI of 1.39 .Inside those figure some sensitivity amplitude curves seem to be flat but they are not actually flat which are shown in the small inside figure. Figure 15 shows linear regression line of the resonance wavelength with the variation of RI of analyte. Through above analysis we observe a linear fitting curve with value R 2 is 0.9939 which provide a better linearity. The sensor quality depends on the linearity response of regression line. The linear regression line equation is y = 2474x 3 − 10072.7x 2 + 13670x – 6186.2 . Where, x is the refractive index and y is the resonance wavelength. Finally, a comparison table 1 has been added to compare the current work with previously published literature in reputed journal with same type of sensing applications. Comparison Table 1: Comparison among the proposed sensor and the existing sensors in terms of fundamental sensor properties such as WS, AS, and wavelength resolution. Ref RI Range Wavelength Sensitivity (nm/RIU) Amplitude Sensitivity (nm/RIU) Wavelength Resolution ((RIU − 1 ) [ 38 ] 1.33–1.35 2520 72.47 3.97 × 10 − 5 [ 39 ] 1.33–1.35 2520 44 2.27 × 10 − 4 [ 40 ] 1.33–1.34 2900 120 N/A [ 41 ] 1.32–1.34 5000 - 2×10 − 5 [ 42 ] 1.33–1.35 2000 - 5 × 10 − 5 [ 43 ] 1.333–1.461 40 - 2.5 × 10 − 4 This work 1.36–1.4 20000 114 1.15 × 10 − 9 Conclusion In this research work a new type of PCF-based plasmonic biosensor has been designed and numerically investigated. The proposed design is very flexible for fabrication because here only circular type of air holes are employed in a very organized way and the air filling factor is moderate level. The sensor has been rigorously investigated for the applied electromagnetic wave. By maintaining all boundary conditions, the proposed plasmonic biosensor offers the utmost wavelength sensitivity of 20000 nm/RIU using wavelength in interrogation method and, maximum amplitude sensitivity of 114 RIU − 1 using amplitude interrogation methods. Moreover, the sensor performance has been also observed for variations in the thickness of plasmonic material. It is worth mentioning that this newly designed sensor offers maximum resolution of 1.15×10 − 9 which makes this design as efficacious for tiny changes of analytes concentration. Based on the superb performance the proposed sensor will highly applicable in clinical and diagnostic, biomedical, applications and many more relevant areas of applications. Declarations Declaration of Competing Interest: The authors affirm that they have no known competing financial benefits or personal relationships that could have appeared to stimulate the work stated in this paper. Funding: There is no external funding for this research work. Author Contribution: Conceptualization SA, SS; methodology, SA, SS, and B. K. P.; software, MKI, B.K.P. ; validation, MAH, and B.K.P. formal analysis, SA and SS ; investigation, SS; resources, MAH, MKI and BKP.; data curation, SA and SS; writing—original draft preparation SA and BKP; writing—review and editing, MAH, MKI , SS and BKP.; visualization, MAH and MKI.; supervision BKP and MAH; References K. V. Stamatios, "Free space optical networks for ultra-broad band services," John Wiley \& Sons, 2011. J. A. Buck, "Fundamentals of Optical Fibers," John Wiley \& Sons, USA, 2nd Edition, 2004 G. P. Agrawal, "Nonlinear Fiber Optics," Academic Press, USA, 2nd Edition, 1995. G. P. 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Wilkinson and J. piehler, "Determination of simazine in water samples by waveguide surface. Plasmon resonance," Analytica Chimica Acta,, Vol. 338, No. 1 -- 2, pp. 109 -- 117, 1997. J. Homola, "Present and future of surface plasmon resonance biosensors," Analytical and bioanalytical chemistry, Vol. 377, No. 3, pp. 528 -- 539, 2003. R. Otupiri, E. Akowuah, S. Haxha, H. Ademgil, F. AbdelMalek and A. Aggoun, "A novel birefrigent photonic crystal fibre surface plasmon resonance biosensor," IEEE Photonics Journal, Vol. 6, No. 4, pp. 1 -- 11, 2014. J. G. Ortega-Mendoza, A. Padilla-Vivanco, C. Toxqui-Quitl, P. Zaca-Morán, D. Villegas-Hernà and F. Chávez, "Optical fiber sensor based on localized surface plasmon resonance using silver nanoparticles photodeposited on the optical fiber end," Sensors, Vol. 14, No. 10, pp. 18701 -- 18710, 2014. E. K. Akowuah, T. Gorman , H. Ademgil, S. Haxha, G.K. Robinson and J.V. Oliver, "Numerical analysis of a photonic crystal fiber for biosensing applications," IEEE Journal of Quantum Electronics, Vol. 48, No. 11, pp. 1403 -- 1410, 2012. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted 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. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-3998814","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":275824195,"identity":"da574f13-46dd-49b2-bc52-83bf12f2abe5","order_by":0,"name":"Sadia Afrin","email":"","orcid":"","institution":"Mawlana Bhashani Science and Technology University","correspondingAuthor":false,"prefix":"","firstName":"Sadia","middleName":"","lastName":"Afrin","suffix":""},{"id":275824196,"identity":"802841be-3858-4c88-96a6-dc418b1af5e9","order_by":1,"name":"Sanchita Sarker","email":"","orcid":"","institution":"Rajshahi University of Engineering and Technology","correspondingAuthor":false,"prefix":"","firstName":"Sanchita","middleName":"","lastName":"Sarker","suffix":""},{"id":275824197,"identity":"9436a2fb-c38c-4b38-bcca-6ccb5743f580","order_by":2,"name":"Bikash Kumar Paul","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAyklEQVRIiWNgGAWjYBACA2Y2BgbGBhsGA7gIQwJRWtKAKpmJ1cIA1nKYBC3m7GyJH3/uOB9tzn/+mARDjR1QhIAWy2a2w9K8Z27n7pyRzCbBcCyZwbLnAQGHHWZvkGZsu5274QYzUAvbAQaDG4T8cpi9+efPtnO5G84fBmr5R5QWtmMSvG0HcjccADqMsY0ILUC/pFnztiWD/GJskdiXzEPQL+b8x4xv/myzy93Of/DhjQ/f7OQIhhgqACrmIUX9KBgFo2AUjAIcAAB31kLSqf9YBAAAAABJRU5ErkJggg==","orcid":"","institution":"Mawlana Bhashani Science and Technology University","correspondingAuthor":true,"prefix":"","firstName":"Bikash","middleName":"Kumar","lastName":"Paul","suffix":""},{"id":275824198,"identity":"40ad90de-5c42-4251-9bf0-fcc29d58b9e4","order_by":3,"name":"Md Abir Hossain","email":"","orcid":"","institution":"Mawlana Bhashani Science and Technology University","correspondingAuthor":false,"prefix":"","firstName":"Md","middleName":"Abir","lastName":"Hossain","suffix":""},{"id":275824199,"identity":"2d04199f-f81f-4a6e-8b1e-abf27a12ea55","order_by":4,"name":"Md Kabirul Islam","email":"","orcid":"","institution":"Daffodil International University Birulia","correspondingAuthor":false,"prefix":"","firstName":"Md","middleName":"Kabirul","lastName":"Islam","suffix":""}],"badges":[],"createdAt":"2024-02-29 07:02:48","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3998814/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3998814/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":52023914,"identity":"9c4b0757-9fa5-4beb-96fa-51fa1ae2450c","added_by":"auto","created_at":"2024-03-05 15:35:01","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":288489,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e1 (a): Proposed sensor two dimensional (2D) cross-sectional view where\u003c/strong\u003e\u003cem\u003e\u003cstrong\u003e d\u003c/strong\u003e\u003c/em\u003e\u003csub\u003e\u003cem\u003e\u003cstrong\u003e1\u003c/strong\u003e\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e\u003cstrong\u003e and d\u003c/strong\u003e\u003c/em\u003e\u003csub\u003e\u003cem\u003e\u003cstrong\u003ec \u003c/strong\u003e\u003c/em\u003e\u003c/sub\u003e\u003cstrong\u003eare the diameter for small and large air holes respectively, and \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003ep\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e is pitch. Here, multiple colors are inserted just for presentation.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e1 (b): Schematic experimental setup for the proposed sensor with essential equipment that helps to detect the label-free analyte.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-3998814/v1/8ba7c3f6688546628f0787f8.png"},{"id":52023915,"identity":"6a463984-7bb6-448c-b009-837e7e303d39","added_by":"auto","created_at":"2024-03-05 15:35:01","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":200217,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eElectro Magnetic field dispersal of (a) core mode (x-pol), (b) core mode (y-pol), (c) SPP mode (x-pol), (d) SPP mode (y-pol)\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-3998814/v1/2c123ec93131b1f49852bcfd.jpeg"},{"id":52024641,"identity":"caffa371-52f4-43bb-a6c0-dabda4447900","added_by":"auto","created_at":"2024-03-05 15:43:01","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":102280,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eConfinement loss curves at analyte RI of 1.36 and 1.37 for tg = 20 nm , 25 nm, 30 nm for X axis.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-3998814/v1/b4a9a968573141b6a63d4e6d.png"},{"id":52023921,"identity":"b27bb275-8bf8-4e88-a46c-eff18c3b23af","added_by":"auto","created_at":"2024-03-05 15:35:02","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":109975,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eConfinement loss curves at analyte RI of 1.36 and 1.37 for t\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003eg\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e = 20 nm , 25 nm, 30 nm for Y Axis.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-3998814/v1/9ea6da23d4beee59b9aa74ed.png"},{"id":52023925,"identity":"282a7942-26c9-4444-a20d-46274042ae5a","added_by":"auto","created_at":"2024-03-05 15:35:02","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":72133,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eAmplitude Sensitivity curves at analyte RI of 1.36 and 1.37 for t\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003eg\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e = 20 nm , 25 nm , 30 nm\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-3998814/v1/ac54dfc7f8ae444470d46a71.png"},{"id":52023923,"identity":"46183fa2-c51f-466d-bce1-74818bb8d40d","added_by":"auto","created_at":"2024-03-05 15:35:02","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":79210,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eAmplitude Sensitivity curves at analyte RI of 1.36 and 1.37 for t\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003eg\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e = 20 nm , 25 nm , 30 nm \u0026nbsp;for Y axis.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-3998814/v1/7b144c0ec3220611bac2979a.png"},{"id":52023919,"identity":"27e972ee-3cb7-4091-a0e4-6d0bb244c6fe","added_by":"auto","created_at":"2024-03-05 15:35:01","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":109645,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eConfinement loss curves at analyte RI of 1.36 and 1.37 for p = 1.9 μm, 1.95 μm , 2 μm.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-3998814/v1/97cd9b8ae1ffa14412bd6f2c.png"},{"id":52023922,"identity":"97029cb4-74b5-4e5f-8b0e-6bc5a2a06eb3","added_by":"auto","created_at":"2024-03-05 15:35:02","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":22918,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eConfinement loss curves at analyte RI of 1.36 and 1.37 for p = 1.9 μm, 1.95 μm, 2 μm .\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-3998814/v1/b70ecae632d552ee309b1b44.png"},{"id":52023926,"identity":"3135ac17-8edb-483f-b48e-0b935793ece1","added_by":"auto","created_at":"2024-03-05 15:35:03","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":75063,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eAmplitude Sensitivity curves at analyte RI of 1.36 for p = 1.9 μm, 1.95 μm , 2 μm.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage10.png","url":"https://assets-eu.researchsquare.com/files/rs-3998814/v1/fac1086d4953209c47d29cf4.png"},{"id":52023913,"identity":"2d9b9a55-9824-4571-bb83-d9eaeebcf135","added_by":"auto","created_at":"2024-03-05 15:35:00","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":48736,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eAmplitude Sensitivity curves at analyte RI of 1.36 and 1.37 for p = 1.9 μm, 1.95 μm, 2 μm.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage11.png","url":"https://assets-eu.researchsquare.com/files/rs-3998814/v1/0fe65e2a55220699b3a30e12.png"},{"id":52024643,"identity":"0dcd6af5-144f-4eff-b901-7ed15791d665","added_by":"auto","created_at":"2024-03-05 15:43:02","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":87974,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eConfinement loss curves for analyte RI from 1.36 to 1.4\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage12.png","url":"https://assets-eu.researchsquare.com/files/rs-3998814/v1/2e67c523b1421c1c801b5e24.png"},{"id":52023927,"identity":"bb970647-13bd-47a0-8b15-c1afc8c1e5e7","added_by":"auto","created_at":"2024-03-05 15:35:03","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":125971,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eConfinement loss curves versus applied wavelength for analyte RI from 1.36 to 1.4 .\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage13.png","url":"https://assets-eu.researchsquare.com/files/rs-3998814/v1/33078679581fffcfa3047ef8.png"},{"id":52023918,"identity":"8bc490ca-f87c-40ae-85ad-6a816fbf4848","added_by":"auto","created_at":"2024-03-05 15:35:01","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":84600,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eAmplitude Sensitivity curves for analyte RI from 1.36 to 1.4 .\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage14.png","url":"https://assets-eu.researchsquare.com/files/rs-3998814/v1/2164ba978fbd69804529bbed.png"},{"id":52023916,"identity":"6b75e256-0f74-44bd-b3ea-c227d615abf7","added_by":"auto","created_at":"2024-03-05 15:35:01","extension":"png","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":99119,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eAmplitude Sensitivity curves for analyte RI from 1.36 to 1.4 .\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage15.png","url":"https://assets-eu.researchsquare.com/files/rs-3998814/v1/d9b90ba5045b5f2f353570ab.png"},{"id":52023917,"identity":"72571126-43ac-48d9-814c-e6d080244c9f","added_by":"auto","created_at":"2024-03-05 15:35:01","extension":"png","order_by":15,"title":"Figure 15","display":"","copyAsset":false,"role":"figure","size":45667,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFitting curves for analyte RI from 1.32 to 1.41\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage16.png","url":"https://assets-eu.researchsquare.com/files/rs-3998814/v1/7f1bbccb225cc128a71405b2.png"},{"id":76125583,"identity":"0636f1cc-2ff1-45bf-b22b-dfb1093a80c7","added_by":"auto","created_at":"2025-02-12 14:24:46","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2549580,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3998814/v1/a0db36ef-16a9-459e-9473-e5630946190b.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Au Coated Photonic Crystal Fiber based Surface Plasmon Resonance Sensor: Design and Investigation","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe silica crystal lattice is extremely transparent and has certain distinctive visual traits. Leveraging these peculiar characteristics, an optical fiber is made. Many engineers and scientists have recently put forward their exceptionally qualified studies toward optical fiber technology and photonic crystal fiber (PCF) technology. PCF is a sort of optical fiber used in modern technology that offers greater stability than standard or traditional optical fiber. It is assembled using a synthetic array of air-filled holes running the length of the fiber.\u003c/p\u003e\n\u003cp\u003ePCF has lingering optical characteristics, including perpetually single-mode operating [\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e], an enormous effective area, ultra-flat dispersion, high nonlinearity, and exceptionally high birefringence, which have all been documented in prior literature [\u003cspan class=\"CitationRef\"\u003e2\u003c/span\u003e]. The size or form of the PCF, the hosting material, the light propagation mechanism, and the operating wavelength mentioned in [\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e] all have a significant impact on these important features; below is a report on them. The two kinds of light that propagate through the PCF are photonic band gap (PBG) and index guiding (IG). In the case of IG-PCF, light is steered through the fiber core because it has a higher refractive index than the surrounding cladding region. Total internal reflection (TIR) of light has taken place here. On the other hand, it has been stated in [\u003cspan class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e6\u003c/span\u003e] that PBG-PCF light can be propagated through the fiber core via the photonic band gap effect. PBG-PCF has a shorter transmission band than IG-PCF of these two types of fiber [\u003cspan class=\"CitationRef\"\u003e4\u003c/span\u003e]. The core of conventional optical fibers was consistently infused with high-index material after initially being manufactured from pure silica [\u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e]. Numerous substances have recently been created as the foundation for PCF. Due to their new optical features described in [\u003cspan class=\"CitationRef\"\u003e9\u003c/span\u003e], tellurite, graphene, and chalcogenide glass with polymer are extensively utilized over an expanded infrared transmission band. PCF fields of application are steadily broadening. It ushered in a new era of swift interaction in the area of telecommunication. The core of the internet is optical fiber. PCF is employed in a variety of fields besides the telecom industry, covering sensing (chemical, gas pressure, and temperature), biological diagnostics, spectroscopy, optical coherence tomography (OCT), high power technology, supercontinuum generation, optical switching, optical amplification, and more [8\u0026ndash;11]. Recently, PCF has caught an extensive amount of attention as a result of diagnostic testing that may identify proteins, germs, and glucose in test samples [\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e16\u003c/span\u003e]. By depicting the brain system, neuroscience is currently experiencing incredible advancement [\u003cspan class=\"CitationRef\"\u003e17\u003c/span\u003e]. PCF has spearheaded a pioneering and unrelenting pursuit of research globally. In the fields of connectivity, along with sensing, microscopy, metrology, astronomical spectroscopy, and numerous other areas, it is only getting started. Sensing is one of the potential applications among these many different fields. A surface plasmon resonance (SPR) sensor based on PCF has recently started vibrating. SPR is a robust, label-free measuring method used to find binding kinetics, chemical affinities, and interactions. It runs on applied light. Polarities are generated as an outcome of the mutual interaction of surface-bound light plasmons. Surface plasmon resonance (SPR), plasmon waveguide resonance (PWR), and plasmon imaging (SPR-I), as well as several other methods, are based on this phenomenon. The communication infrastructure that is included has become more reliant on optical fiber in recent times. Optical fiber is a noteworthy advancement in technology that revolutionized the paradigm of telecommunications. Because of its anonymous performance, which involves signal transmission across farther distances at higher data rates, with little data loss, it gets used in place of copper wire and satellite links [\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e]. In non-telecom sectors that might involve medical imaging, remote sensing, machining, illumination, and so on, optical fiber is also used [\u003cspan class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e]. On average, an optical fiber is a waveguide with a cylindrical shape constructed of two glasses that redirect light signals down its axis. One is a solid glass core featuring a higher refractive index that runs down towards the center of the fiber,the core's inherent light [\u003cspan class=\"CitationRef\"\u003e6\u003c/span\u003e]. The concept of \"conventional optical fiber\" alludes to this sort of optical fiber. Optical fiber has multiple widespread applications in the two distinct telecom and non-telecom sectors, but it additionally comes with several limitations. These constraints are mainly imposed by an assortment of elements, notably the traits of the glass utilized to make it [\u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e], the rigidity of silica glass, and others. A new technique called photonic crystal fiber (PCF) has been developed to get around this restriction. It is sometimes referred to as the holey optical fiber (HOF) or the microstructure optical fiber (MOF) [8]. Eli Yablonovitch and Sajeev John from Bell Communications Research and the University of Toronto both made predictions about the photonic band gap (PBG) in 1987. PBG has emerged as one of the hottest topics in optical technology in the 1990s. The idea was to construct the proper structures to prevent photons with energy levels, or wavelengths, matching PBGs, from passing freely through a fixed wavelength. By drilling holes with a diameter of 1 mm in a block of material with a refractive index of 3.6, Yablonovitch and his associates developed PBG material for the first time in 1991. This structure had a bandgap in the microwave area because the bandgap wavelength is on the order of the distance between the air holes in the photonic crystal. During the CLEO/QELS meeting in 1991, Philip Russell, who was intrigued by Yablonovitch's findings, had a huge \"crazy\" notion for \"something different\" [\u003cspan class=\"CitationRef\"\u003e9\u003c/span\u003e]. By forming a two-dimensional photonic crystal in the cladding that is a periodic wavelength-scale lattice of small air holes in the glass, Russell proposed that light might be captured inside a hollow fiber core. When constructed properly, the photonic crystal cladding that runs the length of the fiber can stop light from escaping from the hollow core. Since they rely on the peculiar characteristics of photonic crystals, these new fibers are referred to as PCFs. In this sort of micro structured optical fiber, the cladding around the cable's core must be shaped using photonic crystals. Surface plasmon resonance (SPR)--based PCF sensors have gained popularity among academics in recent years due to their distinctive characteristics and wide range of practical applications. Due to their high sensitivity, SPR sensors are frequently used in a variety of applications, including water testing [10], maintaining food quality, bio-sensing, medical diagnostics, gas detection, bio-imaging, environment monitoring, real-time monitoring, organic chemical sensing, glucose monitoring, disease detection, and more [11\u0026ndash;15]. Applications based on optical sensors [\u003cspan class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e22\u003c/span\u003e], terahertz sensors [\u003cspan class=\"CitationRef\"\u003e23\u003c/span\u003e], and SPR sensors [11\u0026ndash;15] are being updated quickly to keep up with the development of contemporary technology, Ritchie et al. made the first observation regarding SPR using a theoretical approach in the 1950s [\u003cspan class=\"CitationRef\"\u003e25\u003c/span\u003e]. Liedberg et al. first discussed SPR in 1983 based on prism coupling [\u003cspan class=\"CitationRef\"\u003e26\u003c/span\u003e]. The prism is typically used to activate surface modules. There are some drawbacks to using prism-based SPR sensing devices, such as their hefty size and assortment of optical and mechanical components. Additionally, it is inappropriate for remote sensing applications [\u003cspan class=\"CitationRef\"\u003e27\u003c/span\u003e]. The first optical fiber-based SPR sensor was proposed by R.C. Jorgenson in 1993. To expose the plasmon response, the fiber core was coated with gold film. By using optical fiber for prisms, the aforementioned restriction can be bypassed.\u003c/p\u003e\n\u003cp\u003eTo lower the technical cost and the size of sensor devices, SPR-based sensors are required.\u003c/p\u003e\n\u003cp\u003eBecause of its many appealing properties, such as controllable birefringence, high confinement, and single mode propagation, PCF is also beneficial [\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e25\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e28\u003c/span\u003e]. These features allow for simple manipulation of an evanescent field. Effective, sensitive performance is managed by the evanescent field the PCF-based sensors offer a stunning design as well. In addition, SPR sensors offer higher sensitivity than fiber-based sensors. Additionally, it has a lower peak resistance than fiber-based sensors [\u003cspan class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e30\u003c/span\u003e]. In this paper, we suggest a straightforward spiral PCF structure-based SPR sensor in this study to achieve high sensitivity and low loss properties. This study aims to investigate the performance parameters numerically. By changing a number of the sensor's structural properties, we primarily concentrate on the sensitivity analysis. The numerical analysis is carried out in the extended refractive index (RI) sensing range of 1.36 to 1.4 in both x- and y-polarized modes. Since the plasmonic material is placed on the PCF's outermost layer, it reduces the major fabrication challenges to get the best sensing performance, the impact of altering fiber design factors such as pitch, air hole diameter, and gold layer thickness is examined. An in-depth discussion is also given on potential fabrication methods for the suggested PCF and thin outer gold layer.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eThe geometry of the proposed sensor\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA sensor's construction has a significant impact on its performance. The structural design, i.e., where the air holes are located inside the core, establishes the guiding properties of the sensors and controls their performance. The external sensing-based SPR sensor in this instance uses a hexagonal lattice-based PCF structure with circular air holes and a gold coating. A perfectly matched layer (PML), which reduces undesired nonphysical radiation, is also included to assess the sensor's effectiveness. Double-layer square air holes with circles make up the suggested sensor. Using COMSOL Multiphysics technologies that are readily available on the market, the finite element method (FEM) is used to analyze numerically how well sensor\u0026rsquo;s function. Using the amplitude integration method and the wavelength integration method, respectively, the maximum gain amplitude sensitivity of this elevated structure is 114 RIU and the wavelength sensitivity is 10000 nm/RIU. Applications for the suggested sensor in biophotonics are numerous.\u003c/p\u003e\n\u003cp\u003eFigure\u0026nbsp;1 (a) delineates the 2D cross-section of our proffered sensor. The interspace between the centers of two adjacent air cavities is defined as pitch and is symbolized by p. Two different diameters (d\u003csub\u003e1\u003c/sub\u003e and d\u003csub\u003ec\u003c/sub\u003e) of air holes are utilized for their advantageous behavior. In the cladding region, two hexagonal-shaped clusters, each consisting of ten circular-shaped air holes with a bore of (d\u003csub\u003e1\u003c/sub\u003e), are put down opposite each other along the horizontal axis. Besides, two air holes with the same diameter (d\u003csub\u003e1\u003c/sub\u003e) create two v-shaped arrangements deposited along the vertical axis as mirror reflections. The prudent disposition of the air holes, having a (\u003cem\u003ed\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e) diameter, assists in forming four channels for the propagation of light from the core to the plasmonic mode. The scaled-down corner air holes with a diameter of (d\u003csub\u003e1)\u003c/sub\u003e are employed to limit the confinement loss since these air holes avert light scattering from the focal point of the sensor.\u003c/p\u003e\n\u003cp\u003eThe numerical value of these air hole diameters (\u003cem\u003ed\u003c/em\u003e\u003csub\u003e\u003cem\u003ec\u003c/em\u003e\u003c/sub\u003e = 0.4 \u0026micro;m) has also been selected by the previously mentioned works. The constituent of the fiber is determined to be fused silica (SiO\u003csub\u003e2\u003c/sub\u003e). There are several metals, such as copper (Cu), gold (Au), and silver (Ag), that are utilized as plasmonic materials. Among them, gold shows chemically stable behavior in an aqueous environment and responds with a higher resonance peak. A thin gold layer is employed to encompass the cladding section, and the film thickness is denoted as \u003cem\u003et\u003c/em\u003e\u003csub\u003e\u003cem\u003eg\u003c/em\u003e\u003c/sub\u003e. Since the analyte layer thickness (\u003cem\u003et\u003c/em\u003e\u003csub\u003e\u003cem\u003ea\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e)\u003c/em\u003e is less significant in terms of sensing performance, an arbitrary thickness of 5 \u0026micro;m is decided for this layer. Here, an artificial perfectly matched layer (PML) with a thickness of \u003cem\u003et\u003c/em\u003e\u003csub\u003e\u003cem\u003ePML\u003c/em\u003e\u003c/sub\u003e=1.5 \u0026micro;m is utilized at the outer portion of the computational area to absorb the scattered evanescent field. In a practical sensor, the PML layer is absent, as it is employed only for better simulation purposes. After optimization, regular air hole diameter, pitch, and gold layer thicknesses were found to \u003cem\u003ed\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.8 \u0026micro;m, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;2.0 \u0026micro;m, and \u003cem\u003et\u003c/em\u003e\u003csub\u003e\u003cem\u003eg\u003c/em\u003e\u003c/sub\u003e=30 nm respectively. The schematic experimental setup of the proposed plasmonic biosensor has been demonstrated in Fig.\u0026nbsp;1 (b).\u003c/p\u003e\n\u003cp\u003eThe evanescent field should be directed suitably towards the metal layer so that it may easily interface with the metal layer electrons to provide improved sensing performance. Figures\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e(a) and 2(b) show tight confinement of light, a sign of low CL. Figures\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e(c) and 3(d) make it clear that our proposed sensor exhibits outstanding guiding properties as a result of the strategic arrangement of air holes. A strong core mode-SPP mode coupling is created by the proper interaction of the evanescent field and metal layer. Note that in this context, the terms \"x-polarization\" (x-pol) and \"y-polarization\" (y-pol) refer to the sensor's response to the incidence of, respectively, x-polarized light and y-polarized light. When we positioned the wavelength at 0.8 \u0026micro;m and the concentration of the analyte at 1.36, we obtained SPP mode.\u003c/p\u003e"},{"header":"Numerical Analysis","content":"\u003cp\u003eFor theoretical investigations of different types of PCF properties, numerical analysis is a crucial component. It bases its analysis mostly on the fact that electromagnetic waves are complicated. To investigate and comprehend the propagation of the electromagnetic fields in the photonic crystals, computational methods were created using electromagnetic wave symmetries and periodicities. [\u003cspan class=\"CitationRef\"\u003e30\u003c/span\u003e] In this section, we'll go over the techniques used to calculate the refractive index, confinement loss, sensor resolution, amplitude sensitivity, and wavelength sensitivity of PCFs. Numerous numerical techniques are well known for studying optical phenomena, including finite difference time domain (FDTD), partial wave expansion (PWE), effective mode index (EMI), and full vector-finite element method (FV-FEM). Electromagnetism has been subjected to the FEM. When there is a partial differential equation (PDE) with boundary conditions, the FEM is used in both the physical and engineering sciences. It can be created using different weighted residual methods. Analytical techniques for diverse structures and issues cannot be used to solve these PDEs. These approximations are calculated using the FEM. The finite element method's basic idea is to divide the computation domain into discrete, or finite, subdomains, known as finite elements, and then use straightforward functions, such as linear and quadratic functions, to roughly approximate the unknown solution over each element. All of the PCF's properties listed here are analyzed using COMSOL Multiphysics version 5.5a. Numerical analysis is performed using the Finite Element Method (FEM) and MATLAB version 2016.\u003c/p\u003e\n\u003cp\u003eIn optics, a material's index of refraction, often known as its refractive index, is a dimensionless quantity that characterizes how light moves through that medium. Fused silica serves as the background material in this suggested sensor. It is possible to determine the refractive index of fused silica using Sellmeier's equation no (i) in ref [\u003cspan class=\"CitationRef\"\u003e33\u003c/span\u003e].\u003c/p\u003e\n\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\n\u003cdiv id=\"FileID_Equa\" class=\"mathdisplay\"\u003e$$\\text{n}\\left(\\lambda \\right)=\\sqrt{1+\\frac{{B}_{1}{\\lambda }^{2}}{{\\lambda }^{2}-{C}_{1}}+\\frac{{B}_{2}{\\lambda }^{2}}{{\\lambda }^{2}-{C}_{2}}+\\frac{{B}_{3}{\\lambda }^{2}}{{\\lambda }^{2}-{C}_{3}}} \\dots \\dots \\dots \\dots \\dots \\dots \\dots \\dots \\dots \\dots \\dots \\dots \\dots \\dots \\dots \\dots \\dots \\left(\\text{i}\\right)$$\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eWhere \u003cem\u003en\u003c/em\u003e is refractive index of fused silica that depends on wavelength and \u0026lambda; is the wavelength in \u0026micro;m. \u003cem\u003eB\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e ,\u003cem\u003eB\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e, \u003cem\u003eB\u003c/em\u003e\u003csub\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sub\u003e,\u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e, \u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e, \u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sub\u003e ara the Sellmeir Constants for the background material silica. The values of constants are respectively 0.69616300, 0.407942600, 0.897479400, 4.6791E\u003csup\u003e\u0026minus;\u0026thinsp;15\u003c/sup\u003e \u0026micro;m\u003csup\u003e2\u003c/sup\u003e, 1.3512E\u003csup\u003e\u0026minus;\u0026thinsp;14\u003c/sup\u003e \u0026micro;m\u003csup\u003e2\u003c/sup\u003e and 9.7934E\u003csup\u003e\u0026minus;\u0026thinsp;11\u003c/sup\u003e \u0026micro;m\u003csup\u003e2\u003c/sup\u003e for fused silica.\u003c/p\u003e\n\u003cp\u003eVarious types of loss could happen when light is propagating. Loss due to confinement is one of them. Confinement loss happens when a mode is forced into a tiny area, which causes the mode to partially propagate outside of the fiber (outside of the fiber's core). The following equation (ii) can be used to get the parameters of the sensor's performance evaluation of the confinement loss in ref [\u003cspan class=\"CitationRef\"\u003e35\u003c/span\u003e]:\u003c/p\u003e\n\u003cp\u003e\u0026alpha;\u0026thinsp;=\u0026thinsp;8.686 \u0026times; k0 \u0026times; Im[n\u003csub\u003eeff\u003c/sub\u003e] \u0026times; 10\u003csup\u003e4\u003c/sup\u003e dB/cm \u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;..(ii)\u003c/p\u003e\n\u003cp\u003eWhere, the number of free space is denoted by k\u003csub\u003e0\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;2\u0026pi;/\u0026lambda; operating wavelength is denoted by lambda and the imaginary part of the effective refractive index denoted by Im\u003csub\u003eneff\u003c/sub\u003e\u003c/p\u003e\n\u003cp\u003eThe effectiveness of a PCF-based SPR sensor is evaluated using sensitivity. To calculate the sensitivity, we used the formula shown in equation (iii) in ref [\u003cspan class=\"CitationRef\"\u003e36\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u0026nbsp;\u003cspan class=\"mathinline\"\u003e\\({S}_{\\lambda }\\left(\\frac{nm}{RIU}\\right)=\\frac{\\varDelta {\\lambda }_{peak}}{{\\Delta }{n}_{a}}\\)\u003c/span\u003e\u0026nbsp;\u003c/span\u003e \u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;..(iii)\u003c/p\u003e\n\u003cp\u003eWhen \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\varDelta {\\lambda }_{peak}\\)\u003c/span\u003e\u003c/span\u003e is used to indicate the distinction of wavelength peak shifts and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\Delta }{n}_{a}\\)\u003c/span\u003e\u003c/span\u003eis used to indicate the differenciation of analyte refractive index RI..\u003c/p\u003e\n\u003cp\u003eA short change of analyte RI is possible to accurately detect by using the performance of sensor resolution. Using the following equation (iv) in ref [\u003cspan class=\"CitationRef\"\u003e37\u003c/span\u003e] we obtain the resolution of the raised structure:\u003c/p\u003e\n\u003cp\u003eR(RIU)=\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\left(\\frac{{\\Delta }{n}_{a}\\times \\varDelta {\\lambda }_{min}}{\\varDelta {\\lambda }_{peak}}\\right)\\)\u003c/span\u003e\u003c/span\u003e \u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;.\u0026hellip;\u0026hellip;..(iv)\u003c/p\u003e\n\u003cp\u003eWhere \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\Delta }{n}_{a}=0.01\\)\u003c/span\u003e\u003c/span\u003e, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\varDelta {\\lambda }_{min}=0.1 nm and\\)\u003c/span\u003e\u003c/span\u003e \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\varDelta {\\lambda }_{peak}=maximum\\)\u003c/span\u003e\u003c/span\u003evalue of peak \u0026lambda; differences.\u003c/p\u003e\n\u003cp\u003eThe sensitivity is measured using either the phase detection method or the wavelength interrogation method. Although these technologies are economical, they offer a difficult process to test sensitivity. The amplitude interrogation approach, which measures the amplitude sensitivity at a set wavelength, can, however, be used to solve this issue. It is possible to determine the amplitude sensitivity using the following equation no (v) in ref [\u003cspan class=\"CitationRef\"\u003e38\u003c/span\u003e]:\u003c/p\u003e\n\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u0026nbsp;\u003cspan class=\"mathinline\"\u003e\\({S}_{A}\\left(\\lambda \\right)\\left[RI{U}^{-1}\\right]=-\\frac{1}{\\alpha (\\lambda ,{n}_{a})}\\frac{\\delta \\alpha (\\lambda ,{n}_{a})}{\\delta {n}_{a}}\\)\u003c/span\u003e\u0026nbsp;\u003c/span\u003e \u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;.\u0026hellip;..(v)\u003c/p\u003e\n\u003cp\u003eHere, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\left(\\lambda ,{n}_{a}\\right)\\)\u003c/span\u003e\u003c/span\u003eindicates the overall propagation loss at a specific refractive index RI of analyte and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\left(\\lambda ,{n}_{a}\\right)\\)\u003c/span\u003e\u003c/span\u003eindicates the difference between the two loss spectra.\u003c/p\u003e"},{"header":"Result Analysis","content":"\u003cp\u003eThe section describes the numerical analysis of propagation characteristics in fundamental mode.\u003c/p\u003e\n\u003cp\u003eIn order to procure an enhanced sensing performance, the evanescent field should be maneuvered appropriately towards the metal layer so that it can easily interface with the metal layer electrons. The EM field dispersal of our lodged sensor for both x- and y-polarization modes. Tight confinement of light, which indicates low CL, can be realized from Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e (a) and 2 (b). It is evident from Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e(c) and 2 (d) that our suggested sensor manifests excellent guiding property due to the judicious placement of air holes. Appropriate evanescent field-metal layer interaction forms a robust core mode-SPP mode linkage. Note that, here x-polarization (x-pol) and y-polarization (y-pol) mode refers to the response of the sensor due to the incidence of x-polarized light and y-polarized light, respectively.\u003c/p\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e shows the confinement loss sensor dependent on wavelength with different gold layer thickness t\u003csub\u003eg\u003c/sub\u003e are 20, 25, 30 nm and analyte \u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1.36 and \u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1.37, for the thickness variation of gold layer. The variation process has been executed in a brute force manner At 1.36, when gold thickness is 20 nm the loss becomes lower compare to thickness 30 nm.\u003c/p\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e shows the maximum amplitude sensitivity at thickness \u003cstrong\u003et\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003eg\u003c/strong\u003e\u003c/sub\u003e =20 nm compared to thickness 25 nm and 30 nm. For this reason, we use the thickness 30 nm in our proposed sensor. The amplitude sensitivities of 45, 55, and 63 RIU\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are attained for the t\u003csub\u003eg\u003c/sub\u003e of 20 nm, 25 nm, and 30nm, respectively.\u003c/p\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e represents the confinement loss of proposed sensor dependent on wavelength with different pitch of circle. It has seen from the loss curves in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e. that when the pitch of the circle increases the loss curve decreases a little. For analyte n\u0026thinsp;=\u0026thinsp;1.37 when the pitch is 1.9 \u0026micro;m the peak loss shows 230 dB/cm, for 2 \u0026micro;m the peak loss shows 331 dB/cm and for 1.95 \u0026micro;m the peak loss shows 304 dB/cm .\u003c/p\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e shows the amplitude sensitivity differences among pitches where pitch 1.9 \u0026micro;m gave more sensitivity than 1.95 \u0026micro;m and 2 \u0026micro;m gave highest sensitivity than both 1.9 and 1.95 \u0026micro;m for analyte 1.36 and 1.37. For this reason we use pitch 2 \u0026micro;m in our proposed sensor.\u003c/p\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e12\u003c/span\u003e depicts the variation in Confinement Loss and Resonance Wavelength due to the change in analyte for x- polarization and y- polarization modes. We conducted the sensors performance analysis in the RI range 1.36\u0026ndash;1.4 with an interval of 0.01. The sensor exhibited the peak WS of 114 nm/RIU and 1000 nm/RIU for x-pol and y-pol, respectively which are comparatively high compared to the most other existing SPR based sensors.\u003c/p\u003e\n\u003cp\u003eFigure. 12 and Figure 13 render information regarding the adaptation of Amplitude sensitivity to the modification of RI for x- pol and y-pol. It is undeniable that the AS is proportionate to RI, and with the increase of RI, AS also improves. However, at analyte RI of 1.40 the CL peak curtails along with a broadening of the peak, which effectuates an intense truncation in AS. Regardless of that a max AS of 114 RIU\u003csup\u003e-1\u003c/sup\u003e (x-pol) and 105 RIU\u003csup\u003e-1\u003c/sup\u003e (y-pol) is achieved at an analyte RI of 1.39 .Inside those figure some sensitivity amplitude curves seem to be flat but they are not actually flat which are shown in the\u0026nbsp; small inside figure.\u003c/p\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e15\u003c/span\u003e shows linear regression line of the resonance wavelength with the variation of RI of analyte. Through above analysis we observe a linear fitting curve with value \u003cem\u003eR\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e is 0.9939 which provide a better linearity. The sensor quality depends on the linearity response of regression line. The linear regression line equation is \u003cem\u003ey\u0026thinsp;=\u0026thinsp;2474x\u003c/em\u003e\u003csup\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sup\u003e \u003cem\u003e\u0026minus;\u0026thinsp;10072.7x\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;\u003cem\u003e+\u0026thinsp;13670x \u0026ndash; 6186.2\u003c/em\u003e. Where, \u003cem\u003ex\u003c/em\u003e is the refractive index and \u003cem\u003ey\u003c/em\u003e is the resonance wavelength.\u003c/p\u003e\n\u003cp\u003eFinally, a comparison table 1 has been added to compare the current work with previously published literature in reputed journal with same type of sensing applications.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eComparison Table\u0026nbsp;1: Comparison among the proposed sensor and the existing sensors in terms of fundamental sensor properties such as WS, AS, and wavelength resolution.\u003c/em\u003e\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tabb\" border=\"1\"\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eRef\u003c/em\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eRI Range\u003c/em\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eWavelength Sensitivity\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e(nm/RIU)\u003c/em\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eAmplitude Sensitivity\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e(nm/RIU)\u003c/em\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eWavelength Resolution\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e((RIU\u003c/em\u003e \u003csup\u003e\u003cem\u003e\u0026minus;\u0026thinsp;1\u003c/em\u003e\u003c/sup\u003e\u003cem\u003e)\u003c/em\u003e\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\u003e[\u003cspan class=\"CitationRef\"\u003e38\u003c/span\u003e]\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e1.33\u0026ndash;1.35\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e2520\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e72.47\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3.97 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e[\u003cspan class=\"CitationRef\"\u003e39\u003c/span\u003e]\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e1.33\u0026ndash;1.35\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e2520\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e44\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2.27 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e[\u003cspan class=\"CitationRef\"\u003e40\u003c/span\u003e]\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e1.33\u0026ndash;1.34\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e2900\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e120\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eN/A\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e[\u003cspan class=\"CitationRef\"\u003e41\u003c/span\u003e]\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e1.32\u0026ndash;1.34\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e5000\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e[\u003cspan class=\"CitationRef\"\u003e42\u003c/span\u003e]\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e1.33\u0026ndash;1.35\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e2000\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e5 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e[\u003cspan class=\"CitationRef\"\u003e43\u003c/span\u003e]\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e1.333\u0026ndash;1.461\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e40\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2.5 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eThis work\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e\u003cstrong\u003e1.36\u0026ndash;1.4\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e\u003cstrong\u003e20000\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003e114\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003e1.15 \u0026times; 10\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e\u0026minus;\u0026thinsp;9\u003c/strong\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn this research work a new type of PCF-based plasmonic biosensor has been designed and numerically investigated. The proposed design is very flexible for fabrication because here only circular type of air holes are employed in a very organized way and the air filling factor is moderate level. The sensor has been rigorously investigated for the applied electromagnetic wave. By maintaining all boundary conditions, the proposed plasmonic biosensor offers the utmost wavelength sensitivity of 20000 nm/RIU using wavelength in interrogation method and, maximum amplitude sensitivity of 114 RIU\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e using amplitude interrogation methods. Moreover, the sensor performance has been also observed for variations in the thickness of plasmonic material. It is worth mentioning that this newly designed sensor offers maximum resolution of 1.15\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;9\u003c/sup\u003e which makes this design as efficacious for tiny changes of analytes concentration. Based on the superb performance the proposed sensor will highly applicable in clinical and diagnostic, biomedical, applications and many more relevant areas of applications.\u003c/p\u003e"},{"header":"Declarations","content":" \u003ch2\u003eDeclaration of Competing Interest:\u003c/h2\u003e \u003cp\u003eThe authors affirm that they have no known competing financial benefits or personal relationships that could have appeared to stimulate the work stated in this paper.\u003c/p\u003e \u003ch2\u003eFunding:\u003c/h2\u003e \u003cp\u003eThere is no external funding for this research work.\u003c/p\u003e\u003ch2\u003eAuthor Contribution:\u003c/h2\u003e\u003cp\u003eConceptualization SA, SS; methodology, SA, SS, and B. K. P.; software, MKI, B.K.P. ; validation, MAH, and B.K.P. formal analysis, SA and SS ; investigation, SS; resources, MAH, MKI and BKP.; data curation, SA and SS; writing\u0026mdash;original draft preparation SA and BKP; writing\u0026mdash;review and editing, MAH, MKI , SS and BKP.; visualization, MAH and MKI.; supervision BKP and MAH;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eK. V. Stamatios, \u0026quot;Free space optical networks for ultra-broad band services,\u0026quot; John Wiley \\\u0026amp; Sons, 2011.\u003c/li\u003e\n\u003cli\u003eJ. A. Buck, \u0026quot;Fundamentals of Optical Fibers,\u0026quot; John Wiley \\\u0026amp; Sons, USA, 2nd Edition, 2004\u003c/li\u003e\n\u003cli\u003eG. P. Agrawal, \u0026quot;Nonlinear Fiber Optics,\u0026quot; Academic Press, USA, 2nd Edition, 1995.\u003c/li\u003e\n\u003cli\u003eG. P. 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Felbacq,\u0026ldquo;Foundations of Photonic Crystal Fibers\u0026rdquo;, Imperial Collage Press, London, 2005.\u003c/li\u003e\n\u003cli\u003eY.L. Hoo, W. Jin, J. Ju, H.L. Ho, \u0026ldquo;Numerical investigation of a depressed-index cor crystal fiber for gas sensing\u0026rdquo;, Sens. Actuat. B, vol. 139, pp. 460\u0026ndash;465, 2009.\u003c/li\u003e\n\u003cli\u003eT.M. Monro, D.J. Richardson, P.J. Bennett, \u0026ldquo;Developing holey fiber for evanescent field devices\u0026rdquo;, Electron. Lett., vol. 35, pp. 1188\u0026ndash;1189, 1999.\u003c/li\u003e\n\u003cli\u003eP. Russell, \u0026quot;Photonic Crystal Fibers,\u0026quot; Science, Vol. 299, No. 5605, pp. 358 -- 362, 2003.\u003c/li\u003e\n\u003cli\u003eC. Mouvet, R. Harris, C. Maciag, B. Luff, J. Wilkinson and J. piehler, \u0026quot;Determination of simazine in water samples by waveguide surface. Plasmon resonance,\u0026quot; Analytica Chimica Acta,, Vol. 338, No. 1 -- 2, pp. 109 -- 117, 1997.\u003c/li\u003e\n\u003cli\u003eJ. Homola, \u0026quot;Present and future of surface plasmon resonance biosensors,\u0026quot; Analytical and bioanalytical chemistry, Vol. 377, No. 3, pp. 528 -- 539, 2003.\u003c/li\u003e\n\u003cli\u003eR. Otupiri, E. Akowuah, S. Haxha, H. Ademgil, F. AbdelMalek and A. Aggoun, \u0026quot;A novel birefrigent photonic crystal fibre surface plasmon resonance biosensor,\u0026quot; IEEE Photonics Journal, Vol. 6, No. 4, pp. 1 -- 11, 2014.\u003c/li\u003e\n\u003cli\u003eJ. G. Ortega-Mendoza, A. Padilla-Vivanco, C. Toxqui-Quitl, P. Zaca-Mor\u0026aacute;n, D. Villegas-Hern\u0026Atilde; and F. Ch\u0026aacute;vez, \u0026quot;Optical fiber sensor based on localized surface plasmon resonance using silver nanoparticles photodeposited on the optical fiber end,\u0026quot; Sensors, Vol. 14, No. 10, pp. 18701 -- 18710, 2014.\u003c/li\u003e\n\u003cli\u003eE. K. Akowuah, T. Gorman , H. Ademgil, S. Haxha, G.K. Robinson and J.V. Oliver, \u0026quot;Numerical analysis of a photonic crystal fiber for biosensing applications,\u0026quot; IEEE Journal of Quantum Electronics, Vol. 48, No. 11, pp. 1403 -- 1410, 2012.\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":"Surface Plasmon Resonance, Plasmonic Biosensor, Sensitivity, Photonic crystal fiber","lastPublishedDoi":"10.21203/rs.3.rs-3998814/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3998814/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eWe propose in this research an idiosyncratic, shallow to erect, and highly perceiving Plasmonic material-coated photonic crystal fiber (PCF) based micro-structured biosensor. Our precedence has a cardinal pattern of circular air holes inside the fiber, which leads to a superior sensing performance. The evaluation of all the sensor characteristics has been expelled by sustaining the finite element method (FEM) of COMSOL Multiphysics. The gold (Au) layer just around the fiber acts as the plasmonic material. Gold is picked out due to its high stable rate and maximum resonance peak value in the sensing environment. After the swelling of all the fiber parameters, we derived a maximum amplitude sensitivity (AS) and wavelength sensitivity (WS) of 114 RIU\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 20000 nm/RIU, respectively, with a maximum sensor resolution of 1.15\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;9\u003c/sup\u003e for wavelength. The overall analyte sensing range is from refractive indices 1.36 to 1.4. With its enhanced performance in terms of sensitivity, we believe that this Plasmonic material-coated PCF biosensor can potentially contribute to the detection of unknown analytes.\u003c/p\u003e","manuscriptTitle":"Au Coated Photonic Crystal Fiber based Surface Plasmon Resonance Sensor: Design and Investigation","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-03-05 15:34:54","doi":"10.21203/rs.3.rs-3998814/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":"05c130f4-c14b-480b-afbd-c2b806163bcc","owner":[],"postedDate":"March 5th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-02-12T14:24:10+00:00","versionOfRecord":[],"versionCreatedAt":"2024-03-05 15:34:54","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3998814","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3998814","identity":"rs-3998814","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}