Efficient generation of the second harmonic of a nanosecond CO2 laser radiation pulse

Efficient (49 ± 5%) second harmonic generation was demonstrated for the first time in the infrared. The frequency of CO₂ laser radiation with a pulse duration of ~2 nsec and an intensity of up to 1GW/cm² was doubled in an unbleached ZnGeP₂ crystal. The internal energy efficiency was ~80%.