R. Frank | Searcharxiv

arXiv2011

Scalar Wave Propagation in Random, Amplifying Media: Influence of Localization Effects on Length and Time Scales and Threshold Behavior

We present a detailed discussion of scalar wave propagation and light intensity transport in three dimensional random dielectric media with optical gain. The intrinsic length and time scales of such amplifying systems are studied and comprehensively discussed as well as the threshold characteristics of single- and two-particle propagators. Our semi-analytical theory is based on a self-consistent Cooperon resummation, representing the repeated self-interference, and incorporates as well optical gain and absorption, modeled in a semi-analytical way by a finite imaginary part of the dielectric function. Energy conservation in terms of a generalized Ward identity is taken into account.

cond-mat.dis-nn↗

arXiv2010

Light Transport and Localization in Diffusive Random Lasers

We develop an analytical theory for diffusive random lasers by coupling the transport theory of the disordered medium to the semiclassical laser rate equations, accounting for (coherent) stimulated and (incoherent) spontaneous emission. From the causality of wave propagation in an amplifying, diffusive medium we derive a novel length scale which we identify with the average mode radius of the lasing quasi-modes. We show further that loss at the surface of the laser-active medium is crucial in order to stabilize a stationary lasing state. The solution of the transport theory of random lasers for a layer geometry with appropriate surface boundary conditions yields the spatial profile of the light intensity and of the population inversion. The dependence of the intensity correlation length on the pump rate is in qualitative agreement with experimental and numerical findings.

cond-mat.dis-nn↗