Control system compensates for phase mismatch in nonlinear crystal

Control system compensates for phase mismatch in nonlinear crystal

Thermally induced phase mismatch in a nonlinear optical crystal has been alleviated by a temperature-profile-compensation system, according to researchers at Osaka University (Osaka, Japan) and the Tsukuba R&D Laboratory (Tsukuba, Japan). The system was demonstrated on a CsLiB6O10 (CLBO) crystal that was generating 266-nm ultraviolet (UV) output from a solid-state laser emitting 532-nm pulses with a repetition rate of 100 Hz. The compensation system consisted of a proportion-integral-derivative (PID) controlled heater that housed the CLBO crystal while heating it to 150°C and a jet of cooling gas directed onto the surface of the crystal at the center of the exiting laser beam. The heater reportedly enhanced long-term crystal stability while providing constant UV output from room temperature to 200°C. Cooling gas flow provided the additional benefit of a uniform temperature profile across the laser beam. An output of 10.6 W for 20.3-W input was obtained in a 10-mm crystal and was more than twice the maximum power achieved in the same crystal without the cooling gas flow.