Strong field processes inside gallium arsenide

We demonstrated experimentally that the multiphoton ionization rate in gallium arsenide depends on the alignment of the laser polarization with respect to the crystal axis. We observed modulation in the ionization rate of a linearly-polarized 1900 nm laser beam directly by measuring its transmission while rotating the crystal, without Fourier analysis. We propose that the modulation in the ionization rate arises from periodic variation in the reduced carrier mass, as predicted by Keldysh theory. We show direct comparison of the experimental transmission modulation depth with Keldyshs non-resonant ionization theory for solids. This opens up a novel method for non-invasive crystallography of semiconductor materials. \ua9 2014 IOP Publishing Ltd.Peer reviewed: YesNRC publication: Ye