Parametric amplification of ultrashort 10-μm pulses by two-photon absorption of pump radiation

A numerical investigation was made of the generation of picosecond radiation pulses in the 10-μm wavelength range by parametric amplification of injected 10-μm radiation in the field of high-power ultrashort neodymium laser pulses in a nonlinear proustite (Ag₃AsS₃) crystal. Calculations were carried out in the approximation of plane interacting waves and they allowed for two-photon absorption of the pump pulses and phase modulation of the interacting pulses by an electron density wave. These effects lower the efficiency of parametric amplification by two orders of magnitude (when the pump pulse intensity is 1.2 GW/cm²) and they also result in "pushing" of the signal pulse to the front of the pump pulse and cause its shortening without a significant widening of the spectrum.