Design and Analysis of Rib Waveguide Bragg Grating for Multiplexed Biosensing Application

Over the past decade, waveguide Bragg grating (WBG) sensors have assumed significance in biosensing applications, due to the rapid development in fabrication technology of silicon photonic devices. In this paper, we propose and theoretically analyze a multiplexed biosensor based on surface corrugated Bragg gratings on a Rib waveguide structure using Transfer Matrix method. The Rib waveguide was designed with single mode operating condition at the wavelength of 1550 nm. The effective index is calculated numerically using the Effective Index method and has been verified using Mode Analysis in COMSOL Multiphysics. Highest sensitivity of 44 nm/RIU has been recorded for the design with the smallest dimensions. This design has been further used in the multiplexed biosensing structure by utilizing a cascaded configuration of gratings with two different grating pitches to achieve two distinct Bragg reflection peaks. The sensitivity for the two gratings is calculated to be 44 nm/RIU and 48 nm/RIU. The proposed sensor provides a good sensitivity along with multiplexed sensing and is a viable option when fabrication of smaller dimension sensors is not feasible.