Berlin 2008 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 27: Photonic crystals III

HL 27.6: Talk

Tuesday, February 26, 2008, 17:30–17:45, EW 203

Anderson localization and correlation length in random lasers — •Regine Frank, Andreas Lubatsch, and Johann Kroha — Physikalisches Institut, Universität Bonn, Germany

We present a systematical theory for the interplay of strong localization effects and absorbtion or gain of classical waves in 3-dimensional, disordered dielectrics, which is based on a selfconsistent resummation of self-interference (Cooperon) contributions. In the presence of absorption or gain, Anderson localized modes do not exist in a strict sense. However, in the case of linear gain (i.e. exponential intensity growth), causality in connection with the Cooperon pole structure predicts the appearance of a new finite length scale, which we interpret as the coherence length ξ of a random laser mode. A characteristic dependence of ξ on the gain intensity is found, consistent with experiments. In addition, we solve the fully time dependent problem of the laser rate equations of a 4-level laser (i.e. non-linear gain), coupled to the random gain medium, where the transport of light in the random medium is treated by the self-consistent Cooperon resummation. The results are compared with our semianalytic calculations for the case of linear gain.