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Efficient second harmonic generation of a high-power picosecond CO2 laser.

A comparative analysis of AgGaSe2, GaSe, CdGeAs2, and Te for second harmonic generation (SHG) of a picosecond CO2 laser at intensities up to 50 GW/cm2 is presented. We demonstrate external energy conversion efficiency of >20% in AgGaSe2. Conversion efficiency >5% is measured in GaSe and CdGeAs2. Self-focusing and multifilamentation are found to severely limit the SHG process in CdGeAs2 and Te at such high fields. Demonstration of ≥150 MW SH pulses for a 10 μm picosecond pump, in combination with femtosecond CO2 laser development, will open new strong-field applications in the 4.5-5.5 μm range.