Sum frequency generation under conversion of Q-switched cryogenic slab RF discharge CO laser radiation in ZnGeP₂

Abstract

For the first time broadband sum frequency generation in ZnGeP 2 crystal has been accomplished with a compact cryogenic slab RF discharge CO laser. The spectrum of the CO laser operating in a repetitively pulsed multiline Q-switching mode consisted of ~90 emission lines in the wavelength range of 4.95-6.60 µm. Internal sum frequency generation efficiency was reached up to 8.2%. The resulted spectrum contained ~200 spectral lines in the wavelength range of 2.5-3.2 µm.

Quasiparticle effects on the linear and nonlinear susceptibility of ZnGeP2

“…Zinc germanium diphosphide (ZnGeP 2 ) is one of the most extensively used nonlinear optical material for mid-infrared frequency conversion [1][2][3][4][5] due to its large nonlinear coefficient (d 36 ¼ 75 pm V À1 ), high thermal conductivity (35 W mK À1 ), high damage threshold (1-2 J cm À2 ) as well as its low absorption coefficient (0.1 cm À1 ) in the spectral range of 2.5-8.3 mm. 5,6 The as-grown ZnGeP 2 presents the residual optical absorptions near the pump or generation wavelength, which reduce the opticalto-optical efficiency and raises the crystal elevated temperature.…”