Cascaded Brillouin lasing in monolithic barium fluoride whispering gallery mode resonators

TL;DR

This paper demonstrates cascaded Brillouin lasing at 1550 nm in high-Q monolithic barium fluoride whispering gallery mode resonators, showcasing potential for high-coherence lasers and microwave photonics.

Contribution

It reports the first observation of cascaded Brillouin lasing in BaF2 WGM resonators with ultra-high Q factors, enabling multiple Stokes lines at various frequency shifts.

Findings

Achieved Brillouin lasing at 1550 nm in BaF2 resonators.

Generated multiple Stokes lines with frequency shifts from 8.2 GHz to 49 GHz.

Demonstrated cascaded Brillouin lasing in monolithic resonators.

Abstract

We report the observation of stimulated Brillouin scattering and lasing at 1550~nm in barium fluoride (BaF$_2$) crystal. Brillouin lasing was achieved with ultra-high quality ($Q$) factor monolithic whispering gallery mode (WGM) mm-size disk resonators. Overmoded resonators were specifically used to provide cavity resonances for both the pump and all Brillouin Stokes waves. Single and multiple Brillouin Stokes radiations with frequency shift ranging from $8.2$ GHz up to $49$ GHz have been generated through cascaded Brillouin lasing. BaF$_2$ resonator-based Brillouin lasing can find potential applications for high-coherence lasers and microwave photonics.