Nonlinear pulse compression in inhomogeneous photonic crystals upon backward second harmonic generation

Frequency doubling of phase-modulated laser pulses, which is caused by a quasi-synchronous interaction of counterpropagating waves, is studied theoretically in crystals with an aperiodic domain structure. The simultaneous influence of the change in the domain period and the phase-modulation depth of fundamental radiation on the formation of a second-harmonic pulse is analysed in the nonstationary regime. It is shown that there exists an optimal relation between chirps in an aperiodic crystal and the phase modulation of fundamental radiation at which the maximum nonlinear compression of the second-harmonic pulse duration is possible.