scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Ultrafast laser inscribed waveguide lattice in glass for direct observation of transverse localization of light

05 Mar 2012-Applied Physics Letters (American Institute of Physics)-Vol. 100, Iss: 10, pp 101102
TL;DR: In this paper, the signature of localized light in an ultrafast laser-inscribed (ULI) disordered lattice that contains an array of evanescently coupled, one-dimensional optical waveguides in glass was observed.
Abstract: We present initial results of the direct observation of the signature of localized light in an ultrafast laser-inscribed (ULI) disordered lattice that contains an array of evanescently coupled, one-dimensional optical waveguides in glass in which certain amount of disorder in refractive index was introduced. Numerical simulations were carried out to test the feasibility of the initial experimental design. Such configurable ULI disordered waveguide lattices should open up a platform for investigating the phenomenon of transverse localization of light and its statistical nature.

Content maybe subject to copyright    Report

Citations
More filters
Journal ArticleDOI
TL;DR: In this paper, the authors give an overview of the transverse Anderson localization of light in one and two transverse dimensions, where many aspects of localization are illustrated by means of a few simple models.
Abstract: This tutorial gives an overview of the transverse Anderson localization of light in one and two transverse dimensions. A pedagogical approach is followed throughout the presentation, where many aspects of localization are illustrated by means of a few simple models. The tutorial starts with some basic aspects of random matrix theory and light propagation through and reflection from a random stack of dielectric slabs. Transverse Anderson localization of light in one- and two-dimensional coupled waveguide arrays is subsequently established and discussed. Recent experimental observations of localization and image transport in disordered optical fibers are discussed. More advanced topics, such as hyper-transport in longitudinally varying disordered waveguides, the impact of nonlinearity, and propagation of partially coherent and quantum light, are also examined.

84 citations

Journal ArticleDOI
TL;DR: The impact of the design parameters of the disordered fiber on the beam radius of the propagating transverse localized beam is explored and it is shown that the optimum value of the fill-fraction of the disorder is 50% and a lower value results in a larger beam radius.
Abstract: We recently reported the observation of transverse Anderson localization as the waveguiding mechanism in optical fibers with random transverse refractive index profiles [1]. Here, we explore the impact of the design parameters of the disordered fiber on the beam radius of the propagating transverse localized beam. We show that the optimum value of the fill-fraction of the disorder is 50% and a lower value results in a larger beam radius. We also explore the impact of the average size of the individual random features on the value of the localized beam radius and show how the boundary of the fiber can impact the observed localization radius. A larger refractive index contrast between the host medium and the disorder sites results in smaller value of the beam radius.

80 citations

Journal ArticleDOI
Sunwoo Han1, Ju Hyeon Shin2, Pil Hoon Jung2, Heon Lee2, Bong Jae Lee1 
TL;DR: In this article, a tandem grating solar absorber is proposed, which can be easily fabricated on a wafer scale and is thermally stable up to 800 K, which greatly suppresses the thermal emission loss.
Abstract: In this work, a tandem grating solar absorber is proposed, which can be easily fabricated on a wafer scale and is thermally stable up to 800 K The base of the solar thermal absorber consists of a tungsten substrate, SiO2 spacer, and 2D tungsten nanohole array filled with SiO2 On top of the base structure, a 2D tungsten nanodisc array is coated with an additional SiO2 spacer, forming the tandem grating structure The outside area of the nanodisc array is also filled with SiO2; thus, the proposed solar absorber is geometrically flat In the solar spectrum from 03 to 20 μm, the total absorptance of the fabricated sample is measured to be 90% On the other hand, in the mid-infrared region from 3 to 15 μm, the total emittance is measured to be 23% at 800 K, which greatly suppresses the thermal emission loss Finite-difference time-domain simulation suggests that the magnetic resonance and Rayleigh anomaly are responsible for the enhanced absorption of solar radiation It is also shown that the spectral absorptance of the proposed solar absorber is nearly insensitive to the polarization angle as well as to the incidence angle in the spectrum of solar radiation

69 citations

Journal ArticleDOI
TL;DR: In this paper, a novel S-band multimode Brillouin-Raman random fiber laser based on distributed feedback of Rayleigh scattered light is demonstrated, which relies on a short length, 7.7 km long angle-cleaved dispersion compensating fiber in a mirrorless open cavity.
Abstract: A novel S-band multimode Brillouin–Raman random fiber laser based on distributed feedback of Rayleigh scattered light is demonstrated. It relies on a short length, 7.7 km long angle-cleaved dispersion compensating fiber in a mirror-less open cavity. Two 1425 nm laser diodes at a modest operating power amplify a Brillouin pump (BP) signal, which in turn generates a multi-wavelength laser output through the stimulated Brillouin scattering. Eleven Brillouin Stokes lines, spanning from 1515.15 to 1516.00 nm, were obtained at a Raman pump power of 361.66 mW. Out of these, five odd Brillouin Stokes lines were generated with a flat peak power of about 0 dBm.

46 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present a detailed analysis of the transverse Anderson localization of light in a one-dimensional disordered optical lattice in the language of transversely localized and longitudinally propagating eigenmodes.
Abstract: We present a detailed analysis of the transverse Anderson localization of light in a one-dimensional disordered optical lattice in the language of transversely localized and longitudinally propagating eigenmodes. The modal analysis allows us to explore localization behavior of a disordered lattice waveguide independent of the properties of the external excitation. Various localization-related phenomena, such as the periodic revival of a propagating Anderson-localized beam, are easily explained in modal language. We characterize the localization strength by the average width of the guided modes and carry out a detailed analysis of localization behavior as a function of the optical and geometrical parameters of the disordered lattice. We also show that in order to obtain a minimum average mode width, the average width of the individual random sites in the disordered lattice must be larger than the wavelength of the light by approximately a factor of two or more, and the optimum site width for the maximum localization depends on the design parameters of the disordered lattice.

43 citations

References
More filters
Journal ArticleDOI
Philip W. Anderson1
TL;DR: In this article, a simple model for spin diffusion or conduction in the "impurity band" is presented, which involves transport in a lattice which is in some sense random, and in them diffusion is expected to take place via quantum jumps between localized sites.
Abstract: This paper presents a simple model for such processes as spin diffusion or conduction in the "impurity band." These processes involve transport in a lattice which is in some sense random, and in them diffusion is expected to take place via quantum jumps between localized sites. In this simple model the essential randomness is introduced by requiring the energy to vary randomly from site to site. It is shown that at low enough densities no diffusion at all can take place, and the criteria for transport to occur are given.

9,647 citations

Journal ArticleDOI
Sajeev John1
TL;DR: A new mechanism for strong Anderson localization of photons in carefully prepared disordered dielectric superlattices with an everywhere real positive dielectrics constant is described.
Abstract: A new mechanism for strong Anderson localization of photons in carefully prepared disordered dielectric superlattices with an everywhere real positive dielectric constant is described. In three dimensions, two photon mobility edges separate high- and low-frequency extended states from an intermediate-frequency pseudogap of localized states arising from remnant geometric Bragg resonances. Experimentally observable consequences are discussed.

9,067 citations

Journal ArticleDOI
12 Jun 2008-Nature
TL;DR: This work uses a non-interacting Bose–Einstein condensate to study Anderson localization of waves in disordered media and describes the crossover, finding that the critical disorder strength scales with the tunnelling energy of the atoms in the lattice.
Abstract: Anderson localization of waves in disordered media was originally predicted fifty years ago, in the context of transport of electrons in crystals. The phenomenon is much more general and has been observed in a variety of systems, including light waves. However, Anderson localization has not been observed directly for matter waves. Owing to the high degree of control over most of the system parameters (in particular the interaction strength), ultracold atoms offer opportunities for the study of disorder-induced localization. Here we use a non-interacting Bose-Einstein condensate to study Anderson localization. The experiment is performed with a one-dimensional quasi-periodic lattice-a system that features a crossover between extended and exponentially localized states, as in the case of purely random disorder in higher dimensions. Localization is clearly demonstrated through investigations of the transport properties and spatial and momentum distributions. We characterize the crossover, finding that the critical disorder strength scales with the tunnelling energy of the atoms in the lattice. This controllable system may be used to investigate the interplay of disorder and interaction (ref. 7 and references therein), and to explore exotic quantum phases.

1,379 citations

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

Journal ArticleDOI
12 Jun 2008-Nature
TL;DR: This work directly image the atomic density profiles as a function of time, and finds that weak disorder can stop the expansion and lead to the formation of a stationary, exponentially localized wavefunction—a direct signature of Anderson localization.
Abstract: Anderson localization (AL) is a phenomenon in wave physics, occurring when interference between multiple scattering paths causes diffusion to cease. Experimentally, localization has been reported for light waves, microwaves, sound waves and electron gases, but there has been no direct observation of AL for matter waves of any type. The paper reports AL in a Bose–Einstein condensate as it expands in a one-dimensional disordered optical potential. The authors image directly the atomic density profiles as a function of time, and find that weak disorder can stop the expansion and lead to the formation of a stationary exponentially localized wave function — a direct signature of AL. The method can be extended to localization of atomic quantum gases in higher dimensions, and with controlled interactions. In 1958, Anderson predicted the localization1 of electronic wavefunctions in disordered crystals and the resulting absence of diffusion. It is now recognized that Anderson localization is ubiquitous in wave physics2 because it originates from the interference between multiple scattering paths. Experimentally, localization has been reported for light waves3,4,5,6,7, microwaves8,9, sound waves10 and electron gases11. However, there has been no direct observation of exponential spatial localization of matter waves of any type. Here we observe exponential localization of a Bose–Einstein condensate released into a one-dimensional waveguide in the presence of a controlled disorder created by laser speckle12. We operate in a regime of pure Anderson localization, that is, with weak disorder—such that localization results from many quantum reflections of low amplitude—and an atomic density low enough to render interactions negligible. We directly image the atomic density profiles as a function of time, and find that weak disorder can stop the expansion and lead to the formation of a stationary, exponentially localized wavefunction—a direct signature of Anderson localization. We extract the localization length by fitting the exponential wings of the profiles, and compare it to theoretical calculations. The power spectrum of the one-dimensional speckle potentials has a high spatial frequency cutoff, causing exponential localization to occur only when the de Broglie wavelengths of the atoms in the expanding condensate are greater than an effective mobility edge corresponding to that cutoff. In the opposite case, we find that the density profiles decay algebraically, as predicted in ref. 13. The method presented here can be extended to localization of atomic quantum gases in higher dimensions, and with controlled interactions.

1,357 citations