Some characteristics of nonlinear interaction of wave packets in media with quadratic nonlinearity

Numerical solutions are used in an investigation of some features of the nonlinear interaction of wave packets (pulses or beams) in quadratic media. Three types of interaction are considered: the interaction of escaping waves with a pump wave, the interaction of concurrent and escaping waves, and the interaction of spatially confined waves. It is shown that a near-100 % conversion of the pump pulse energy into the energy of low-frequency fields can be achieved for all three types of interaction. A study is made of the possibility of generation of ultrashort pulses in the three-frequency interaction. It is shown that, in particular, when confined fields with a low initial amplitude are amplified in the field of a long pump pulse, this pump pulse becomes shortened and its maximum intensity increases considerably.