Optical biosensor based on a cladding modulated grating waveguide

We have proposed and analyzed a photonic biosensor based on a cladding modulated grating waveguide comprising of the three channels on silicon-on-insulator (SOI) platform. The optical mode is propagated in the center channel and the other two channels interacted with the lateral field. Gratings are designed in the outer channels and parameters are optimized to get a narrow stopband in the transmission spectra. The analysis of the proposed configuration is performed through the eigenmode expansion (EME) method. For a sensing, shift in a resonant band is utilized for a change in a refractive index of a biomaterial. The structure is evaluated for three-waveguide thickness (220 nm, 150 nm, and 100 nm) by considering the fabrication tolerances. The sensor structure with a 100 nm thickness has delivered a higher sensitivity of 322.96 nm/RIU with a limit of detection of the order of 1.03 × 10−4 RIU. A designed sensor is easy to fabricate using existing CMOS fabrication facility and can be used for an application of lab-on-chip devices.