Optical detection in GaSe

Optical detection in gallium selenide was investigated for the first time. The nonlinear susceptibility coefficients of optical detection were determined for the emission frequencies of CO₂, neodymium, and ruby lasers and for the second harmonic of the neodymium laser. These coefficients were compared with the values calculated employing a model of a bound charge and those found experimentally in the case of second harmonic generation. Allowances were made for the contribution of interband transitions. The main contribution to optical detection came from the lattice.