Development of a SiON-based integrated platform for the blue/nearUV wavelength range

Driven by the rich variety of molecular and atomic spectral features to probe in the NUV (near ultraviolet), photonic devices operating in this spectral range, like coherent sources and optical functions, may address multiple applications such as biosensing, environment, and security issues. Leveraging from mature semiconductor manufacturing industry, silicon photonics and in particular Silicon On Insulator (SOI) has emerged, over the past two decades, as the preferred technology for photonic integration. However, due to its low energy bandgap, Silicon strongly absorbs at wavelengths shorter than 1100 nm, prohibiting the use of SOI platform at near-UV wavelengths. To circumvent the Si absorption issue at short wavelengths, different materials, including Si3N4, Al2O3 or polymers, have been proposed to achieve low propagation loss in the blue and violet spectrum range. This paper presents the use of silicon oxynitride (SiOxNy) to develop a platform enabling the development of near-UV integrated photonics. The optical design of integrated ridge waveguides for single-mode propagation at near-UV wavelengths is presented. Physical characterizations (refractive index, rugosity) of Plasma Enhanced Physical Vapor Deposition (PECVD) deposited SiOxNy on silica and fabrication process of integrated ridge waveguides using i-lines photolithography and RIE dry etching techniques are then described. To characterize these integrated waveguides, a microlensed fiber is developed in the NUV to improve the coupling efficiency between the fiber and the input of the integrated waveguide based on SiOxNy. Single-mode propagation of near-UV light (405 nm) is also observed in ridge structures by optical near field imaging.