Tuning the resonances of high Q-factor whispering gallery mode resonators for optoelectronic applications

Abstract

Optical resonators allow highly efficient light-matter interaction; therefore, they are promising tools for optoelectronics and photonics. Especially optical resonators with high Q-factors such as toroidal resonators can be instrumentalized to develop efficient light sources, modulators, converters, and sensitive detectors. They are already being used for photonics research; however, some significant obstacles hinder their mass utilization in the industry. One of those obstacles is the current limitations of the fabrication method used to produce toroidal resonators. Due to the method used to achieve surface tension-induced microresonators (STIM), their fabrication is time-consuming. A new approach was presented to mass-produce STIMs. Instead of a fixed position laser, a raster scan laser was used to reflow the microresonators with different geometry types to overcome the mass-fabrication limitations. As a result, high-Q-factor (10^6) toroidal resonators were fabricated. Reflowing of elliptical and racetrack resonators were also demonstrated. Another problem that hinders the utilization of toroidal resonators is their high susceptibility to any errors originating from the fabrication process. Any deviation from the designed parameters leads to resonators with different resonant modes. A method for post-production tuning resonant mode of chalcogenide coated resonator was demonstrated. By using a thin Ge2Sb2Te5 layer coated silica toroidal resonator, 0.01 nm and 0.02 nm permanent mode shifts were achieved from 5 nm thick coated and 10 nm thick coated resonators, respectively.