Coherent effects in wave propagation through complex media
"Diffusion is a powerful and versatile description of a typical wave propagation in a random scattering medium that disregards phase and, thus, a possibility of interference. Speckle, transmission fluctuations, wave localization, non-local correlations, and transmission eigenchannels are examples of persistent interference effects, which arise in the course of deterministic propagation. Such wave phenomena contain a wealth of information about the medium and the source of waves, enabling sensing and coherent control of the propagation. The nonlocal correlations and speckle statistics of the partially coherent light are used to uncover an object hidden by a diffusive cloak inside a strong scattering medium. It is shown that it is possible to detect the size and position, including the depth, of the object unknown apriori. In addition, a theoretical model is developed to predict the geometry dependence of the transmission eigenchannels and intensity correlations. It is demonstrated that deformation of the geometry of the system offers a predictable approach to coherent control of wave propagation in random media that is complementary to wavefront shaping. Lastly, a class of critical states embedded in the continuum is uncovered in a one-dimensional optical waveguide array with one non-Hermitian defect. These states are on the verge of being fractal and have real propagation constants, exhibiting a phase transition from delocalization to localization as the imaginary part of the refractive index in the defect waveguide approaches a critical value"--Abstract, page iv.
Missouri University of Science and Technology
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