Abstract

Backward stimulated Brillouin scattering (SBS) is known to feature a narrow gain bandwidth, for instance, a few tens of MHz in fluoride crystals. Here, we reveal an approach to broaden the Brillouin gain using crystalline whispering gallery mode resonators (WGMRs). The crystalline orientation can result in a large variation of the acoustic phase velocity along the periphery. It helps in forming an over 2.5 GHz wide Brillouin gain in a z-cut magnesium fluoride cavity, which is verified both theoretically and experimentally.

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