In-situ tuning of whispering gallery modes of levitated silica microspheres

TL;DR

This paper demonstrates in-situ tuning of whispering gallery modes in levitated silica microspheres by annealing, with a focus on understanding the thermal processes involved and achieving significant spectral shifts.

Contribution

It introduces a method for in-situ WGM tuning during optical levitation using annealing, analyzing the thermal balance and cooling mechanisms involved.

Findings

Achieved up to 1% blue shift in WGMs.

Identified air conduction as the dominant cooling process.

Demonstrated in-situ tuning during optical levitation.

Abstract

We demonstrated the tuning of whispering gallery modes (WGMs) of a silica microsphere during optical levitation through the annealing process. We determined the annealing temperature from the power balance between the CO2 laser light heating and several cooling processes. Cooling caused by heat conduction through the surrounding air molecules is the dominant process. We achieved a blue shift of the WGMs as large as 1 \%, which was observed in the white-light scattering spectrum from the levitated microsphere.