A nonperturbative quantum theory for phonon-assisted photon absorption of conduction band electron in intense laser was developed. By carrying out the calculation in fused silica at wavelengths from ultraviolet to infrared in terawatt intensity laser, we show that the nonperturbation approach can make a uniform description of energy absorption rate at both short wavelengths and long wavelengths on terawatt per centimeter square intensity laser.

A theory of photon-assisted impact ionization in solids is presented. Our theory makes a quantum description of the new impact ionization-cold avalanche ionization recently reported by P. P. Rajeev, M. Gertsvolf, P. B. Corkum, and D. M. Rayner [Phys. Rev. Lett. 102, 083001 (2009)]. The present theory agrees with the experiments and can be reduced to the traditional impact ionization expression in the absence of a laser.

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