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.