Free-electron Auger quenching of the Fe2+ excited state in ZnSe

The influence of free electrons in Fe²⁺ : ZnSe crystals on the nonlinear transmission of high-power laser radiation with a wavelength of 2940 nm at room and low temperatures is experimentally found. Fe²⁺ : ZnSe samples additionally doped with Al are used. The transmission of an Al : Fe : ZnSe sample with electron conduction in a strong (peak intensity about 4.6 MW cm^-2) field is almost the same as in a weak field both at low and room temperatures. The absence of an increase in the transmission of this sample under the action of high-power radiation is explained by increasing absorption saturation intensity of Fe²⁺ at this wavelength due a decrease in the lifetime of the excited state of Fe²⁺. The decrease in the lifetime is related to the well-known Auger quenching of impurity luminescence in semiconductors by free electrons.