Brillouin lasing in coupled silica toroid microcavities

TL;DR

This paper reports the demonstration of Brillouin lasing in a coupled silica toroid microcavity system, utilizing mode splitting to match the Brillouin frequency shift and enabling low-power lasing without precise cavity size control.

Contribution

It introduces a novel coupled microcavity approach that simplifies Brillouin lasing by tuning mode splitting through cavity gap adjustment.

Findings

Achieved 11 GHz mode splitting matching silica's Brillouin shift

Demonstrated SBS lasing with resonant amplification

Potential for low-threshold lasing in small cavities

Abstract

We demonstrate stimulated Brillouin scattering (SBS) lasing in a strongly coupled microcavity system. By coupling two silica toroid microcavities, we achieve large mode splitting of 11 GHz, whose frequency separation matches the Brillouin frequency shift of silica. The SBS light is resonantly amplified by pumping at the higher frequency side of the supermode splitting resonance. Since the mode splitting is adjusted by changing the gap distance between the two cavities, our system does not require precise control of a mm-sized cavity diameter to match the free-spectral spacing with the Brillouin frequency shift. It also allows us to use a small cavity, hence our system has the potential to achieve the lasing threshold at a very low power.