Miniature wavelength-selectable Raman laser: new insights for optimizing performance

We report a miniature, wavelength-selectable crystalline Raman laser operating either in the yellow (588 nm) or lime (559 nm) selected simply by changing the temperature of an intracavity LBO crystal. Continuous-wave (CW) output powers are 320 mW and 660 mW respectively, corresponding to record diode-visible optical conversion efficiencies of 8.4% and 17% for such miniature devices. The complex laser behavior arising from interplay between nonlinear processes is studied experimentally and theoretically. We show that the interplay can lead to complete suppression of the first-Stokes field and that the phase matching conditions for maximum visible powers differ markedly for different length LBO crystals. By using threshold measurements, we calculate the round-trip resonator losses and show that crystal bulk losses dominate over other losses. As a consequence, Raman lasers utilizing shorter LBO crystals for intracavity frequency mixing can produce higher visible output power. These are new considerations for the optimum design of CW intracavity Raman lasers with visible output.