Broadband CO Laser with Intracavity Frequency Conversion for Plasma Diagnostics

In this work, we experimentally study intracavity frequency conversion of CO laser radiation in a nonlinear ZnGeP2 crystal under noncritical phase matching. Various configurations of a laser cavity are considered, in one of which the nonlinear crystal itself was an output mirror. The spectrum of the converted radiation was shifted into the short-wavelength region owing to the temperature tuning of the phase matching in the nonlinear crystal. The maximum average lasing power was obtained at room temperature of the crystal and an output mirror with a transmission T similar to 10% for the fundamental band and reached similar to 7.0 mW. The power ratio of sum frequency generation and the CO laser radiation was similar to 16%, which turned out to be higher than the value obtained earlier with the BaGa2GeSe6 crystal (11.5%) at the same laser facility.