  The dynamics of photonic wavepacket in the effective oscillator potential is
studied. The oscillator potential is constructed on a 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 a nonlinear response of the system. Numerical estimations for
porous-silicon based structures are presented for femtosecond Ti:Sapphire laser
pump.
