Towards all-glass monolithic realization of arbitrary whispering gallery mode resonators

Whispering gallery mode resonators can support high-quality resonances, which are commonly accessed through evanescent coupling using a tapered fibre that is aligned using external translation stages. To reduce complexity, we first introduce a compact system that consists of a tapered fibre passively aligned to the resonator. The resonator and the mechanical structure that holds it are both fabricated monolithically in a single substrate using fs-laser induced modifications and chemical etching, while the resonator itself is achieved through CO2-laser reflow. We optimise the coupling to the resonator by actuating the holder in another fs-laser exposure step, which allows for precise alignment on the nm-scale. Pushing the system integration further, we explore a significantly simplified and robust system that is obtained through the monolithic fabrication of both the waveguide and the resonator in a single substrate. Our approach is promising for applications that require both miniaturisation and high precision alignment.