Investigation of a Subwavelength Grating Bimodal Interferometric Sensor Built on Silicon Nitride Platform

We design a bimodal interference sensor on a 400-nm-thick silicon nitride (SiN) platform, using a subwavelength grating (SWG) waveguide structure. By optimizing the structure parameters, the sensor exhibits a bulk sensitivity of ~2100 nm/RIU and the surface sensitivity of ~0.72 nm/nm. Compared with its counterparts in silicon, our device has similar performance, but can already be fabricated with accessed commercial foundry.