Criteria of efficiency of SHG of powerful femtosecond laser pulse (Q2769623)

A frequency transformation, particularly the second-harmonic generation (SHG) of femtosecond laser pulses, is the fundamental problem of femtosecond nonlinear optics. It is known that in the last 5 years numerous attempts to create a frequency convertor for femtosecond impulses with an efficiency near to 100 accompanying SHG femtosecond impulses have been made. A systematical analysis of the nonlinear effects is possible only on a base of computer modelling. In this connection, in order to construct conservative difference schemes, it is necessary to write down the invariants (conservation laws) of light waves interactions. An unknown invariant of the problem is found in the article. On the bases of the invariant, a particular solution of the problem is found and a criterion of efficiency of SHG of powerful femtosecond laser pulses is written down.