Raman process under condition of radiation trapping in a disordered atomic medium

Abstract

We consider the Raman process developing in a disordered medium of alkali-metal atoms when the scattered modes are trapped on a closed transition. Our theoretical analysis, based on numerical simulations of the Bethe-Salpeter equation for the light correlation function, which includes all Zeeman states and light polarization, lets us track the stimulated amplification as well as the losses associated with the inverse anti-Stokes scattering channel. We discuss possible conditions when this process could approach the instability point and enter the regime of random lasing.

Random lasing in an inhomogeneous and disordered system of cold atoms

“…Then the portion of light, originally created in the spontaneous Raman process and then propagating via multiple scattering through the disordered atomic ensemble can stimulate additional Raman emission. If we imbalanced the trapping conditions in such way that the amplification of the transported light overcome its losses, then we could arrive at the situation of a random lasing mechanism as discussed in [29]. We briefly summarize that result below.…”

“…where we introduced the scattering cross section σ sc (ω) with the scattering tensor, which for the scattering on a dressed atom is specified in [29].…”

Mesoscopic coherence in light scattering from cold, optically dense and disordered atomic systems

“…If we unbalance the trapping conditions in such way that the amplification of the transporting light overcomes its losses, then we would arrive at the situation of a random lasing mechanism as discussed in the previous section. This mechanism has been recently considered in [68].…”

“…We only have to take into account the complete structure of the retarded type polarization operator given by the sum of diagrams (4.1). The details of the calculations are presented in [68] and we only discuss here the final results.…”

“…As was commented on in [68] the problem with the extra losses, related to the control mode nonlinearity, can be solved for in a spatially inhomogeneous configuration. The crucial requirement is to separate the amplification and trapping areas.…”