Dynamical Casimir effect in microwave cavities containing nonlinear crystals

I consider a possibility of parametric amplification of the microwave vacuum field in a reentrant cavity enclosing a nonlinear crystal whose refractive index is modulated by periodic high-intensity short laser pulses. The main result is that the total number of created 'Casimir quanta' depends neither on the laser beam shape, nor on the duration or power of individual pulses, but it depends on the total energy of all the pulses, provided the duration of each pulse is much shorter than the period of field oscillations in the selected resonant mode. The scheme can be feasible if reliable materials with high nonlinear coefficients can be found.