High-order mid-IR multiphoton absorption and nonlinear refraction in GaP, ZnSe, GaSe, and ZGP crystals

Using Z-scan and femtosecond 2.35-µm pulses, we study high-order nonlinear effects in monocrystals. We find the multiphoton absorption order N varies from N=6 (GaP, ZnSe) to N=4 (GaSe, ZGP), in accordance with the crystals’ bandgaps.