Power scaling of efficient diamond Raman lasers with 1240 nm and 1485 nm output

This paper reports on an external-cavity diamond Raman laser of output power 14.5 W and quantum conversion efficiency 65%. The laser was pumped by a 30 W Q-switched Nd:YVO₄ laser delivering 20 ns pulses at 36.5 kHz pulse repetition frequency. The laser threshold was 6.9 W. Up to 3 W was generated at 1240 nm and 13 W was generated at 1485 nm in the eye-safe spectral region. The overall power conversion efficiency was 48.5%. This device represents a substantial improvement in efficiency when compared to other high power crystalline Raman lasers. It also demonstrates that the external-cavity Raman laser efficiencies routinely seen at the 1-2 W output power level are sustainable at powers up to 15 W. Thermal lensing was also investigated in the external cavity diamond Raman laser, and made comparison to a Raman laser with similar pumping and resonator conditions that used KGW as the Raman medium. This comparison between KGW and diamond in similar resonators gives insight to thermal design issues when scaling to higher Raman output powers and estimates possible power limitations.