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Observation of Anderson localization in disordered nanophotonic structures

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Science  02 Jun 2017:
Vol. 356, Issue 6341, pp. 953-956
DOI: 10.1126/science.aah6822

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Localizing light at the nanometer scale

Waves will propagate through a medium until scattering processes result in the excitation gradually dying away. Introducing disorder can affect that propagation by increasing the scattering, potentially reaching a point where transport is stopped. Typically, the length scale of the disorder is larger than the propagating waves. Herzig Sheinfux et al. now show that a stack of several-nanometer-thick layers of alternating high- and low-refractive- index material can result in the localization of light. Such deep-subwavelength structures could provide a route to manipulating light on the nanometer scale.

Science, this issue p. 953

Abstract

Anderson localization is an interference effect crucial to the understanding of waves in disordered media. However, localization is expected to become negligible when the features of the disordered structure are much smaller than the wavelength. Here we experimentally demonstrate the localization of light in a disordered dielectric multilayer with an average layer thickness of 15 nanometers, deep into the subwavelength regime. We observe strong disorder-induced reflections that show that the interplay of localization and evanescence can lead to a substantial decrease in transmission, or the opposite feature of enhanced transmission. This deep-subwavelength Anderson localization exhibits extreme sensitivity: Varying the thickness of a single layer by 2 nanometers changes the reflection appreciably. This sensitivity, approaching the atomic scale, holds the promise of extreme subwavelength sensing.

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