Characterization of ZnGeP2 for parametric generation with near-infrared femtosecond pumping

Abstract

Values for the nonlinear refractive index (n(2) approximate to 5.4 X 10(.5) cm(2)/GW) are reported as well as the two-photon absorption coefficient (beta approximate to 0.25 cm/GW) in ZnGeP02 at wavelengths near half the band edge of this semiconductor nonlinear optical crystal. The Z-scan measurements were performed with a mode-locked femtosecond Cr:forsterite laser at 1.26 mum and 83 MHz, and the nonlinear transmission measurements were accomplished by a near infrared traveling wave optical parametric generator providing powerful femtosecond pulses at 1 kHz. In both cases, ZnGeP2 samples with reduced anomalous absorption were used. The parametric fluorescence in these 2-mm thin ZnGeP2 samples was studied with near infrared pumping and the optimum pump wavelength established lies between 1.9 and 2.1 mum. The femtosecond signal and idler pulses generated could be tuned between 2.5 and 12 mum at a maximum single pass internal conversion efficiency of 2.5%