STOCHASTIC EFFECTS OF THE SOLVENT ON THE ABSORPTIVE AND DISPERSIVE PROCESSES IN A 2-LEVEL SYSTEM UP TO FIRST-ORDER IN THE EXTERNAL-FIELD

We have considered the stochastic effect of a thermal reservoir on a t wo-level system interacting with a classical electromagnetic field. Th e collective effect of the bath is modelled in this work as a random B ohr frequency whose manifestation is the broadening of the upper level according to a prescribed random function. This assumption transforms the optical Bloch equations to a system of multiplicative stochastic differential equations whose solution is found. After obtaining analyt ical expressions for the linear absorption coefficient and linear refr action index, numerical results are presented. This is done in the for m of tridimensional plots of the optical properties as a function of t he pump-frequency detuning factor and the strength or relaxation time of the noise source.