  We consider classical and quantum electromagnetic fields in a
three-dimensional (3D) cavity and in a waveguide with oscillating boundaries of
the frequency $\Omega $. The photons created by the parametric resonance are
distributed in the wave number space around $\Omega/2 $ along the axis of the
oscillation. When classical waves propagate along the waveguide in the one
direction, we observe the amplification of the original waves and another wave
generation in the opposite direction by the oscillation of side walls. This can
be understood as the classical counterpart of the photon production. In the
case of two opposite walls oscillating with the same frequency but with a phase
difference, the interferences are shown to occur due to the phase difference in
the photon numbers and in the intensity of the generated waves.
