Silica microtoroid resonator sensor with monolithically integrated waveguides.

Due to their wide operating range, silica toroidal whispering gallery mode microresonators have enabled numerous applications from fundamental physics to lasing and sensing. However, the integration of a waveguide with these microresonators has not been achieved which limits their integration with additional on-chip components. Here, we demonstrate a novel approach for monolithically integrating a silica microtoroid with an on-chip waveguide to form a fully integrated microtoroid-waveguide system with quality factors in excess of 4 million. Similar to the conventional toroidal cavities, power-independent operation is demonstrated. UV and temperature sensing experiments are also performed using the monolithically integrated microtoroid-waveguide system.