Two-photon absorption in GaSe and CdGeAs2

We measured two-photon absorption (TPA) coefficients, at room temperature, for two noteworthy mid-infrared nonlinear-optical crystals, namely GaSe and CdGeAs2 in the wavelength range corresponding to E-g/2 < (h) over bar omega < E-g. We used the nonlinear transmittance technique, employing different types of nano- and picosecond lasers with wavelengths ranging from 0.68 to 2.8 mu m, and the dynamic range of laser intensities spanning 6 orders of magnitude. TPA coefficients were found to be beta = (6 +/- 1.2) x 10(-9) cm/W for GaSe (at lambda approximate to 700 nm) and beta = (2.5 +/- 0.5) x 10(-7) cm/W for CdGeAs2 (at lambda approximate to 2.8 mu m). (C) 1998 Elsevier Science B.V. All rights reserved.