Third-harmonic and fourth-harmonic generations of CO2 laser radiation in a GaSe crystal

Tunable third-harmonic and fourth-harmonic generations of pulsed CO2 laser radiation in a GaSe crystal were demonstrated. The optical properties of GaSe and phase-matching conditions in harmonic generations were investigated. The output peak powers for 3.2 μm and 2.4 μm were measured to be 1500 W and 320 W, with corresponding conversion efficiency from 9.6 μm of 0.1% and 0.02%, respectively.