Average power and brightness scaling of diamond Raman lasers

Diamond holds substantial promise as a high Raman gain laser material with outstanding power handling capability, yet despite this the highest reported output power from a diamond Raman laser prior to this project was approximately 1 W. This report describes investigations into order-of-magnitude power scaling of diamond Raman lasers. The investigations focus on 1064 nm beam conversion of 50 W lasers in the external cavity Raman cavity configuration in both pulsed and continuous wave modes of operation. For pulsed operation, output powers up to 16 W are demonstrated with 40-50% conversion efficiency from a compact acousto-optically Q-switched neodymium pump laser. The output power is similar to the highest achieved by other groups (in diamond and other Raman materials) but with much greater efficiency and using a much simpler overall system. More than 13 W is also demonstrated at the second-Stokes wavelength at 1.49 micron in the so-called eye-safe region, a result which compares well in terms of efficiency as well as power with alternative leading high pulse rate eye-safe laser technologies. The model-backed experiments suggest thermal effects are negligible at the current power levels, and much higher output powers are likely when using high power pumps. For CW operation, output powers up to 16 W are demonstrated with conversion efficiency up to 40%. Efficiencies more closely approaching the quantum limit (86%) may be enabled by future improvements in diamond quality. As far as we are aware these are the first demonstrations of CW Raman conversion in a discrete all-solid-state system at multi-watt powers. We show that the concept is applicable for output powers up to several hundred watts and holds promise as a widely applicable technology for high power CW conversion. We also report findings of a UV etching mechanism for diamond surfaces.