Plasmonic refractive index sensor based on metal insulator metal waveguide

Abstract

We proposed and analyze numerically an ultra high figure of merit based refractive index sensor in Plasmonic Bragg grating. Structure is simulated by FDTD (Finite difference time domain) method under a PML (perfectly matched layer) absorbing boundary condition. Silver metal is used as metallic part in MIM (Metal insulator metal) waveguide geometry and insulating layer is taken as air. Permittivity of metal is frequency dependent and is characterized by Drude model. The Bragg grating is analyzed as a sensor by changing the parameters of defect area. Various Structures are analyzed by tailoring the block length of the defect waveguide from 0.3 µm to 0.5 µm and keeping block width constant (0.2 µm). Sensitivity is computed by detecting change in resonant wavelength for per unit change in RIU (Refractive Index Unit). Large value of sensitivity obtained is 1535 nm/ RIU. Also high value of quality factor (Q=242) and Figure of Merit (FOM=152) is reported with the optimized structural parameter. The proposed design can be a suitable choice for refractive index sensor. Thus, this device is suited to design optical sensor circuits.