Nonlinear absorption and refraction in CuCl at 532 nm

We report two-photon absorption in CuCl and its polarization dependence to give all three χ(3) tensor elements at 532 nm. We also report bound electronic n2 and free-carrier refraction in CuCl. The values obtained are each approximately one half the corresponding values for ZnSe. Previously, with ZnSe, the large two-photon absorption (2PA) and negative bound-electronic nonlinear refraction were combined with defocusing from 2PA-generated free carriers to provide effective optical limiting for visible picosecond input pulses. For nanosecond pulses thermal refraction is a problem because it leads to self focusing, and thus damage in ZnSe and most other semiconductors studied. However, the thermal refraction in CuCl is reported to be self-defocusing. Thus one might expect the self-protection properties of CuCl to be better than those of ZnSe for optical-limiting applications for nanosecond input pulses.