SPR-based fiber optic sensor in NIR region

摘要

A surface plasmon resonance (SPR) based fiber optic sensor is simulated and analyzed in near infrared (NIR) region fornormal (N) and malignant human liver tissue (MET) detection. Proposed five layered sensor consists of samarium-dopedchalcogenide core, silver layer (Ag) deposited on the polymer clad, followed by graphene monolayer and analyte layer.Transfer matrix method for N layer model has been used for normalized reflection coefficient ® calculations for theproposed multilayer structure. Furthermore, sensor structure utilizes the selective ray launching where incident angle() is varied at fiber input end (angular interrogation) and power transmitted through sensing region of length ‘L’ ismeasured in dB. At resonance (i.e., α = αSPR), sharp power loss peak is obtained where, αSPR shifts to other angle (i.e.SPR) with a change in analyte refractive index (RI). The prime focus of the present study is to optimize the radiativedamping (i.e., optimum radiative damping (ORD)) at Ag-graphene junction to bring significant enhancement in thesensor’s performance. At resonance condition, the interference between incident light and back-scattered light knownas radiation damping is responsible for excessively large sensor’s figure of merit (FOM). Hence, the coupled role ofmetal layer thickness (dm) and wavelength (λ) with 2D material layer plays important role as extent of radiation dampingchanges significantly, which leads to massive increase in FOM. For the proposed sensor structure value of L/D is takenas 25 (D represents the fiber core diameter) achievable with various L and D combinations (e.g., L = 1 cm and D = 400m). The combination of dm = 35 nm and λ = 865 nm leads to a maximum FOM of 4910.32 RIU-1. The coupled effectof dm and λ leads to significantly higher value of FOM, enables the graphene-based fiber-optic sensor for biosensing andother applications.