Sensitivity Enhanced SPR Biosensor Based On Dual-Core Photonic Crystal Fiber

Surface Plasmon Resonance(SPR)based Photonic crystal fiber(PCF)Biosensors have gained much research attention these days.These biosensors are used to detect pathogens,toxins,antibodies and proteins etc.and support wide range of applications such as Health diagnostics,Biomedicine,biochemical analysis and Environmental field monitoring.The wider design spaces in PCF SPR Biosensors offer the greater index contrast between the core and the cladding of the Fiber as compared to the conventional Fibers using SPR biosensors based on the Kretschmann configuration with bulky prisms.The existing PCF refractive index sensors usually use weak fiber evanescent field to excite plasma resonance effect,resulting in poor SPR sensitivity.In addition,traditional fiber-optic biosensors use microfluidic devices outside the fiber to perform sensing experiments,so they are larger in size and more complex in structure.This thesis presents a dual-core PCF SPR biosensor(SPR DC-PCF).The simulation design uses two techniques:Finite-Element method(circularly applied)and Perfectively Matched layer(for boundary condition)to illustrate the sensing characteristics of Biosensor in COMSOL.To meet the practical fabrication standards,a thin circular layer(20 nm)of Silver(Ag)material is deposited inside the Fiber as an oxidation-free and cheap metal.The proposed design introduces the analyte layer(sensing)in the center of the Fiber to achieve the smaller sensor size and easy handling of guided modes in the electromagnetic field for the better sensitivity as compared to the previous designs.The designed biosensor shows the Wavelength sensitivity of 80,000 nm/RIU and resolution of 1 × 10-4 RIU under the wavelength interrogation method for 1.340 to 1.346 refractive indices(RIs).Under Amplitude interrogation method,Biosensor shows 997 RIU-1 of sensitivity value and 1 × 10-4 RIU of Resolution for the same refractive indices.This improved biosensor design has linear behavior of resonant wavelengths against the change in the structural properties and reasonable Figure of Merit(FOM).Simulation results shows that the sensitivity of traditional PCF is 10,000nm/RIU.Compared with it,the maximum sensitivity of the DC-PCF proposed in thesis is 80,000nm/RIU.The improvement in the maximum sensitivity can enhance the ability of the biosensor to detect the smallest change in the refractive index of the analyte.By comparing the various indicators of each biosensor,such as structure,sensing method and refractive index range,this thesis effectively validates that the designed dual-core photonic crystal fiber biosensor has good performance.This optical fiber sensor is expected to play a role in biochemical detection,biomedicine,and environmental detection.