Efficient frequency conversion of pulsed microchip and fiber laser radiation in PPSLT

Extensive studies on frequency doubling with ppSLT crystals are presented. This includes a detailed discussion on design aspects and theoretical modeling predictions as well as experimental studies comparing the performance of ppSLT crystals from different providers with and without MgO doping. Experimental analyses of their acceptance parameters and crystal homogeneity are conducted with a pulsed microchip laser with low peak (6 kW) and low average power (50 mW) resulting in a maximum conversion efficiency of up to 80 % for high quality MgO doped crystals. Based on these results a compact converter module with fiber coupling is designed and tested with the radiation from the microchip laser and a fiber laser source in comparison. The fiber laser provides an average power of about 1 W. Even at this - still very moderate - power level a significant efficiency drop can be observed. Despite the advantage of higher pulse peak (25 kW) power from the fiber laser source, careful design adaptations of the converter are required even to preserve a conversion efficiency beyond 50%.