Efficient generation of the second harmonic of CO2 laser radiation in a GaSe crystal

Efficient generation of the second harmonic of CO₂ laser pulses was achieved in GaSe single crystals at repetition frequencies up to 100 Hz. The phase-matching angles were measured for GaSe at pump wavelengths of 9.3, 9.6, 10.3, and 10.6 μm. The threshold power densities for surface optical damage and for the formation of a plasma jet on the surface of GaSe were determined. The efficiency of second harmonic generation in a GaSe crystal 0.65 cm thick was up to 9%. A comparison was made of GaSe and ZnGeP₂ crystals as materials suitable for the generation of the second harmonic of CO₂ laser radiation.