High-order harmonic generation from solid surfaces in intense laser fields

Abstract

We give a Floquet analysis of high-order harmonic generation from a solid surface interacting with intense laser fields. A general theoretical algorithm, within a three-dimensional quasi-free electron model, is presented. It takes account of the effective masses of the electron both within and outside the solid and treats both reflected and refracted laser fields. The high-order harmonic spectrum is obtained from the off-diagonal photon components of the expectation value of the time-dependent current operator. We present the formation of a plateau, well known in the atomic case, in the spectrum of the high-order harmonic radiation, which arises from the evanescent part of the electron wave function at the surface.