On the Theoretical Analysis of Parametric Amplification of Femtosecond Laser Pulses in Crystals with a Regular Domain Structure

The parametric amplification of ultrashort (femtosecond) laser pulses in crystals with a regular domain structure (RDS) of the 5%Mg : PPLN type has been investigated theoretically. The focus was on the formation of a signal pulse in dependence of the dispersion of the medium and cubic nonlinearity. It is shown that a small deviation of the size of domains from their exact value, determined by the coherent length of nonlinear interaction of optical waves, may increase to a great extent the efficiency of signal-wave generation. The reason is that the phase shifts due to the third-order nonlinearity and dispersion of the medium (as a rule, they affect only the generalized phases of nonlinear wave interaction) may be partially compensated by the influence of the "excess" wave number of nonlinear lattice. The optimal domain sizes, at which the efficiency of signal-wave generation under conditions of self-action and nonstationarity becomes maximum, have been analyzed based on the results obtained.