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Coherently amplifying random medium: Statistics of super-reflection

Kumar, Narendra and Pradhan, Prabhakar and Jayannavar, AM (1998) Coherently amplifying random medium: Statistics of super-reflection. In: Superlattices and Microstructures, 23 (3-4). pp. 853-857.

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Light-wave propagation in a randomly scattering but uniformly and coherently amplifying optical medium is analysed for the statistics of the coefficient of reflection r(l) that may now exceed unity, hence super-reflection. Uniform coherent amplification is introduced phenomenologically through a constant negative imaginary part added to the otherwise real dielectric constant of the medium, assumed random. The probability density p (r, I) for the reflection coefficient, calculated in a random phase approximation, tends to an asymptotic form p(r, infinity) having a long tail with divergent mean (r) in the limit of weak disorder but with the sample length I (measured in units of the localization length in the absence of gain) much greater than 1. This super-reflection is attributed to a synergetic effect of localization and coherent amplification, as distinct from the classically diffusive path-length prolongation. Our treatment is based on the invariant-imbedding method for the one-channel (single-mode) case, and is in the spirit of the scattering approach to wave transport as pioneered by Landauer. Generalization to the multichannel case is pointed out. Relevance to random lasers, and some recent results for a sub-meanfree path sample are also briefly discussed.

Item Type: Journal Article
Publication: Superlattices and Microstructures
Publisher: Academic Press
Additional Information: Copyright of this article belongs to Academic Press.
Keywords: random laser;localization;amplification;fluctuations.
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 13 Mar 2009 10:17
Last Modified: 19 Sep 2010 05:00
URI: http://eprints.iisc.ac.in/id/eprint/18261

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