Optimization of an optical waveguide biosensor based on hybrid coupler with short-range surface plasmon polariton

The presented study is an analysis of an integrated sensor based on a dielectric waveguide structure with Gold nanolayer. It consists of a short-range surface Plasmon polariton (SRSPP) generating hybrid coupler and a SiNx dielectric waveguide. The output transmission spectra of the sensor is observed to change significantly with the refractive index of the detection liquid, and the sensing region can be adjusted by varying the length and thickness of it. For ultra-thin layer bimolecular detection, the application of the wavelength interrogation method has been shown here. It is also shown that varying the thickness of layers can give rise to spectral changes. A brief analytical formulation of the SPP excitation and the comparison of this with the simulated results, which are accomplished using the finite element method via the COMSOL Multiphysics software have been presented. The scope of the study includes the spectral responses of the sensor configuration in energy domains, with varying analytes and thickness of layers along with the advantages and disadvantages of the different combinations these attributes. This sensor is expected to have significantly high effective sensitivity for detecting a hundred-nanometer-thick layer owing to the highly bounded field of the SRSP mode.