The effects of laser field fluctuations on multiphoton excitation of a multilevel system

In this paper we analyze the effects of the fluctuations of laser amplitude on the multiphoton excitation of a sparse multilevel molecular system. It is found that contrary to the excitation by a laser with phase fluctuations, the stochastic contribution of the amplitude fluctuations is non-diagonal and scrambles the off-diagonal elements of the general molecular density matrix, resulting in temporal oscillations of these terms. The chaotic field model for the laser amplitude cannot force the applicability of the kinetic master equation for a general multilevel system. It is found that, for the two-level system driven by a chaotic field model laser, The stochastic interlevel rate dumps the oscillatory behaviour of the molecular populations, validating the master equation by T₁-type effects.