Response of Si and InSb to ultrafast laser pulses

We present simulations of the response of Si and InSb to femtosecond-scale laser pulses of various intensities. In agreement with the experiments by various groups on various materials, there is a non-thermal phase transition for each of these semiconductors above a threshold intensity. Our simulations employ semiclassical electron-radiation-ion dynamics (SERID), a technique which is briefly described in the text. We also introduce a new addition to the technique, which provides a simple treatment of the correction due to motion of the atomic-orbital basis functions. We find that this correction is small in the present context, but it may be substantial in situations with more rapid atomic motion. Our expression for this correction is remarkably simple to employ because it amounts to nothing more than a generalized Peierls substitution.