Silicon nitride (SiNx), has been widely regarded as a CMOS photonics enabling material, facilitating the development of low-cost CMOS compatible waveguides and related photonic components. We have previously developed an NH3-free SiN PECVD platform in which its optical properties can be tailored. Here, we report on a new type of surface-emitting nitrogen-rich silicon nitride waveguide with antenna lengths of L > 5 mm. This is achieved by using a technique called small spot direct ultraviolet writing, capable of creating periodic refractive index changes ranging from -0.01 to -0.04. With this arrangement, a weak antenna radiation strength can be achieved, resulting in far-field beam widths < 0.015 0 , while maintaining a minimum feature size equal to 300 nm, which is compatible with DUV scanner lithography.

Silicon nitride films with different compositions are exposed to ultraviolet light using both an LED and a laser as light sources (with a wavelength of 244 nm and 265 nm, respectively). Collected data suggests a decrease in refractive index following the exposure, and this can be used for permanently tuning the response of passive photonic devices. The effects of ultraviolet illumination on the material are studied combining observations of the change in the response of the photonic devices and analysis of exposed films.