Theory for the electron excitation in dielectrics under an intense circularly polarized laser field

We report a Keldysh-like model for the electron transition rate in dielectrics under an intense circularly polarized laser. We assume a parabolic two-band system and the Houston function as the time-dependent wave function of the valence and conduction bands. Our formula reproduces the experimental result for the ratio of the excitation rate between linear and circular polarizations for $\alpha$-quartz. This formula can be easily introduced into simulations of nanofabrication using an intense circularly polarized laser.