Molecular dynamics computer simulation of non-linear optical effects; electric polarisation due to optical rectification in a circularly polarised laser

Abstract

The technique of field applied molecular dynamics computer simulation is used to investigate the picosecond molecular dynamics of static and dynamic electric polarisation due to a laser field. A pulse of intense, circularly polarised, electromagnetic radiation is applied to a sample of chiral molecules and the molecular dynamics analysed statistically with time correlation functions computed in the presence of the laser. The effect of the laser on the molecular dynamics was animated and analysed visually. These dynamics measure the interaction between the imaginary part of the dynamic electronic polarisability and the conjugate product Π A of the laser. When the laser frequency is tuned to the THz region (corresponding to picosecond time scales of the natural molecular dynamics) the computer simulation shows the presence of frequency dependent magnetisation, measured by the t→∞ level of the component of the angular momentum correlation function in the axis of propagation of the laser. In general, the details of the molecular dynamic response are very sensitive to the frequency and intensity of the laser.