Non-Perturbative Modeling of Ultrafast Photoionization of Transparent Solids: From the Keldysh Formula to a Model for Few-Cycle Laser Pulses

Based on the Keldysh concept of laser-driven electron oscillations, we overview recent progress in development of non-perturbative approaches to simulation of the photoionization of non-metal crystals by few-cycle ultrashort laser pulses with non-zero spectral bandwidth.