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Proceedings ArticleDOI

Effect of phase front curvature on transverse localization of a light beam

TL;DR: In this article, the significance of the plane phase front in light localization in a disordered medium from application point of view is studied and the results show the advantage of plane phasefront irrespective of the input beam profile.
Abstract: The significance of beam's phase front in light localization in a disordered medium from application point of view is studied. The results show the advantage of plane phase front irrespective of the input beam profile.
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Journal ArticleDOI
01 Mar 2007-Nature
TL;DR: The experimental observation of Anderson localization in a perturbed periodic potential is reported: the transverse localization of light caused by random fluctuations on a two-dimensional photonic lattice, demonstrating how ballistic transport becomes diffusive in the presence of disorder, and that crossover to Anderson localization occurs at a higher level of disorder.
Abstract: One of the most interesting phenomena in solid-state physics is Anderson localization, which predicts that an electron may become immobile when placed in a disordered lattice. The origin of localization is interference between multiple scatterings of the electron by random defects in the potential, altering the eigenmodes from being extended (Bloch waves) to exponentially localized. As a result, the material is transformed from a conductor to an insulator. Anderson's work dates back to 1958, yet strong localization has never been observed in atomic crystals, because localization occurs only if the potential (the periodic lattice and the fluctuations superimposed on it) is time-independent. However, in atomic crystals important deviations from the Anderson model always occur, because of thermally excited phonons and electron-electron interactions. Realizing that Anderson localization is a wave phenomenon relying on interference, these concepts were extended to optics. Indeed, both weak and strong localization effects were experimentally demonstrated, traditionally by studying the transmission properties of randomly distributed optical scatterers (typically suspensions or powders of dielectric materials). However, in these studies the potential was fully random, rather than being 'frozen' fluctuations on a periodic potential, as the Anderson model assumes. Here we report the experimental observation of Anderson localization in a perturbed periodic potential: the transverse localization of light caused by random fluctuations on a two-dimensional photonic lattice. We demonstrate how ballistic transport becomes diffusive in the presence of disorder, and that crossover to Anderson localization occurs at a higher level of disorder. Finally, we study how nonlinearities affect Anderson localization. As Anderson localization is a universal phenomenon, the ideas presented here could also be implemented in other systems (for example, matter waves), thereby making it feasible to explore experimentally long-sought fundamental concepts, and bringing up a variety of intriguing questions related to the interplay between disorder and nonlinearity.

1,368 citations


"Effect of phase front curvature on ..." refers background or methods in this paper

  • ...The light wave propagation in disordered media is governed by the Schrödinger like equation as given in [4]....

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  • ...Introduction Localization of light has already been reported in disordered optical media [1-4]....

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  • ...In one of the recent papers, Schwartz et al [4] have experimentally verified the 2D light localization in a disordered lattice and discussed the interplay between certain aspects of nonlinearity and disorderness....

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Journal ArticleDOI
TL;DR: An intermediate regime is found in which the ballistic and localized components coexist while diffusive dynamics is absent and evidence is found for a faster transition into localization under nonlinear conditions.
Abstract: We experimentally investigate the evolution of linear and nonlinear waves in a realization of the Anderson model using disordered one-dimensional waveguide lattices. Two types of localized eigenmodes, flat-phased and staggered, are directly measured. Nonlinear perturbations enhance localization in one type and induce delocalization in the other. In a complementary approach, we study the evolution on short time scales of delta-like wave packets in the presence of disorder. A transition from ballistic wave packet expansion to exponential (Anderson) localization is observed. We also find an intermediate regime in which the ballistic and localized components coexist while diffusive dynamics is absent. Evidence is found for a faster transition into localization under nonlinear conditions.

792 citations


"Effect of phase front curvature on ..." refers background in this paper

  • ...Introduction Localization of light has already been reported in disordered optical media [1-4]....

    [...]

Journal ArticleDOI
TL;DR: It is shown that a system with transverse disorder in two directions exhibits strong two-dimensional localization by demonstrating that on propagation a beam expands until the transverse localization length is reached.
Abstract: We study the propagation of light through a semi-infinite medium with transverse disorder (that is, disorder in two directions only). We show that such a system exhibits strong two-dimensional localization by demonstrating that on propagation a beam expands until the transverse localization length is reached.

262 citations


"Effect of phase front curvature on ..." refers background in this paper

  • ...We may mention that in [1], light localization was studied in terms of Hamiltonian of the optical system....

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  • ...Introduction Localization of light has already been reported in disordered optical media [1-4]....

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Journal ArticleDOI
TL;DR: In this paper, the authors show that disorder limits how much light can be slowed, and that localization leads to spatially concentrated and locally trapped light in a quasi-one-dimensional waveguide at wavelengths near the band edge.
Abstract: Slowing down light on a chip can lead to the development of optical buffers1, filters2,3 and memory elements4 useful for optical interconnects and for resonantly enhanced chip-based nonlinear optics5,6. Several approaches to slow light rely on the phenomenon of light interference in a sequence of coupled resonators1,2,3,4,7,8,9,10,11; however, light interference is also responsible, in disordered structures, for the localization of light, an effect particularly prominent in one-dimensional devices12,13. Until now, the length of the waveguides investigated has been less than the localization length. Here we report the first observation of light localization in compact silicon nanophotonic slow-light waveguides consisting of long sequences of coupled resonators. Our results show that disorder limits how much light can be slowed, and that localization leads to spatially concentrated and locally trapped light in a quasi-one-dimensional waveguide at wavelengths near the band edge.

152 citations


"Effect of phase front curvature on ..." refers background in this paper

  • ...Introduction Localization of light has already been reported in disordered optical media [1-4]....

    [...]