We demonstrate a continuous-wave diamond Brillouin laser (DBL) in a ring cavity, operating near 532 nm with a 167 GHz Stokes shift. The DBL is pumped by a narrow-line (<1 MHz), frequency-doubled ytterbium fiber laser with the intracavity power resonantly enhanced via Hänsch-Couillaud locking. The measured threshold enabled the Brillouin gain coefficient in diamond to be determined for the first time, yielding a value of 60 cm/GW for pump and Brillouin polarizations aligned parallel to the 〈111〉 crystallographic direction in diamond (determined by the cut of our diamond in this case). Analysis of diamond’s photoelastic tensor shows that for polarization aligned to 〈110〉 for maximum gain, a coefficient of 115 cm/GW can be deduced, the highest bulk Brillouin gain coefficient reported for any material. The high Brillouin gain coefficient in combination with outstanding optical and thermal properties, indicates great potential for realizing diamond lasers and stimulated Brillouin scattering-enabled devices of performance far exceeding other materials.
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