4 March 2016 Evidence of Anderson localization effects in random Raman lasing
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Anderson localization, also known as strong localization, is the absence of diffusion in turbid media resulting from wave interference. The effect was originally predicted for electron motion, and is widely known to exist in systems of less than 3 dimensions. However, Anderson localization of optical photons in 3 dimensional systems remains an elusive and controversial topic. Random Raman lasing offers the unique combination of large gain and virtually zero absorption. The lack of absorption makes long path length, localized modes preferred. The presence of gain offsets what little absorption is present, and preferentially amplifies localized modes due to their large Q factors compared with typical low Q modes present in complex media. Random Raman lasers exhibit several experimentally measured properties that diverge from classical, particle-like, diffusion. First, the temporal width of the emission being 1 to a few nanoseconds in duration when it is pumped with a 50 ps laser is a full order of magnitude longer than is predicted by Monte Carlo simulations. Second, the random Raman laser emission is highly multi-mode, consisting of hundreds of simultaneous lasing modes. This is in contrast to early theoretical results and back of the envelope arguments that both suggest that only a few modes should be present. We will present the evidence that suggests a divergence from classical diffusion theory. One likely explanation, that is consistent with all of these anomalies, is the presence of high-Q localized modes consistent with Anderson localization.
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Brett H. Hokr, Alexander Cerjan, Jonathan V. Thompson, Luqi Yuan, Seng Fatt Liew, Joel N. Bixler, Gary D. Noojin, Robert J. Thomas, Hui Cao, A. Douglas Stone, Benjamin A. Rockwell, Marlan O. Scully, and Vladislav V. Yakovlev "Evidence of Anderson localization effects in random Raman lasing", Proc. SPIE 9731, Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications XV, 973110 (4 March 2016); doi: 10.1117/12.2212911; https://doi.org/10.1117/12.2212911

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