Efficient second harmonic generation of a high-power picosecond CO_2 laser

A comparative analysis of AgGaSe_2, GaSe, CdGeAs_2, and Te for second harmonic generation (SHG) of a picosecond CO_2 laser at intensities up to 50 GW/cm^2 is presented. We demonstrate external energy conversion efficiency of >20% in AgGaSe_2. Conversion efficiency >5% is measured in GaSe and CdGeAs_2. Self-focusing and multifilamentation are found to severely limit the SHG process in CdGeAs_2 and Te at such high fields. Demonstration of ≥150 MW SH pulses for a 10 μm picosecond pump, in combination with femtosecond CO_2 laser development, will open new strong-field applications in the 4.5–5.5 μm range.