Mode Sensitivity Analysis of Subwavelength Grating Slot Waveguides

In this paper, we investigate the mode sensitivity ( $S_{mode}$ ) of subwavelength grating slot (SWGS) waveguides. $S_{mode}$ is an important parameter in various waveguide-based photonic circuits such as sensors, modulators, and thermally-controlled devices. It is a measure of the sensitivity of the waveguide effective index towards the refractive index perturbations in the cladding medium. The SWGS waveguide exhibits high mode sensitivity, as it combines sensitivity enhancement features of both slot and subwavelength grating waveguides. Finite-difference time-domain simulations are performed for the analysis, design, and optimization of the hybrid structure. The SWGS waveguide is incorporated into a Mach-Zehnder interferometer and fabricated on a silicon-on-insulator platform for the experimental estimation of $S_{mode}$ . The measured $S_{mode}$ value of 79% is consistent with the theoretical prediction of 83%.