Silicon nitride waveguide platform for on-chip spectroscopy at visible and NIR wavelengths

On-chip spectroscopy in visible and near-infrared wavelength offers immense potential for various screening and diagnostic application. Silicon Nitride (SiN) is a promising material to realize on-chip spectroscopy as it is transparent over a broad wavelength spectrum; visible-to-mid-infrared. Besides, it is compatible with the CMOS process technology. Since SiN can be deposited using various deposition techniques, it is essential that an appropriate deposition process is chosen to achieve desired properties. We present a detailed study of SiN films deposited using PECVD and LPCVD process. The films were characterized for various, material and optical properties. We also performed waveguide transmission measurement on different SiN films and found a strong correlation with material properties such as stress and autofluorescence to achieve low-loss waveguide. Using the optimized material, we design, fabricate, and demonstrate single-mode SiN wire, spiral waveguides and grating fiber-chip coupler at visible (λ =520nm) and near infra-red (λ = 780nm) wavelengths used for spectroscopy.