On-Chip Ultra-High-Q Silicon Oxynitride Optical Resonators

Ultra-high-quality-factor (UHQ) optical resonators have enabled numerous fundamental scientific studies and advanced integrated photonic device technology. While free-standing devices can be fabricated from many different materials, only silica (SiO 2 ) devices have been successfully integrated onto silicon wafers in large arrays. However, the UHQs ( Q > 10 8 ) are transient, gradually decaying over time due to the presence of hydroxyl groups on the silica surface that attract water. Here, we overcome this challenge by using silicon oxynitride (SiO x N y ) instead of silica. Unlike SiO 2, SiO x N y presents a mixture of −OH and −F groups to the environment, thus inhibiting the formation of a high optical loss water layer. As a result, quality factors in excess of 100 million are able to be maintained for longer than 14 days with no environmental controls on device storage. Over the same time frame, quality factors for SiO 2 devices stored in the same manner degraded by approximately an order of magnitude.