Mid-IR high-order multiphoton absorption and nonlinear refraction in GaP, ZnSe, GaSe, and ZGP crystals

Abstract

Using Z-scan and femtosecond 2.35-µm pulses, we study high-order nonlinear effects – multiphoton absorption (MPA) and nonlinear refraction (n2) in several notable mid-IR nonlinear monocrystals. We find that the multiphoton absorption orders N vary from N=4 (GaSe, ZGP) to N=6 (GaP, ZnSe) and correspond to the crystals’ bandgaps.