Optical echo in photonic crystals

The dynamics of a photonic wavepacket in the effective oscillator potential is studied. The oscillator potential is constructed on the base of one-dimensional photonic crystal with a period of unit cell adiabatically varied in space. The structure has a locally equidistant discrete spectrum. This leads to an echo effect, i.e., the periodical reconstruction of the packet shape. The effect can be observed in the nonlinear response of the system. Numerical estimations for porous-silicon based structures are presented for a femtosecond Ti:sapphire laser pump.