Anderson Localization Of Light Research Articles

Retroreflection of light from nanoporous InP: correlation with high absorption

Pronounced retroreflection behavior is reported for a fishnet nanoporous strongly absorbing semiconductor material. Retroreflection appears along with diffusive specular reflection for all angles of incidence for light wavelength corresponding to interband optical transitions, where absorption coefficient is of the order of 105 cm−1 (green and red light). Retroreflection is apparent by the naked eye with daylight illumination and exhibits no selectivity with respect to wavelength and polarization of incident light featuring minor depolarization of retroreflected light. Retroreflection vanishes for wavelength corresponding to optical transparency range where photon energy is lower than the InP bandgap (1.064 μm). The phenomenon can be classified neither as coherent backscattering nor as Anderson localization of light. The primary model includes light scattering from strongly absorptive and refractive super-wavelength clusters existing within the porous fishnet structure. We found that retroreflection vanishes for wavelength where absorption becomes negligible.

Electronic control of optical Anderson localization modes

Anderson localization of light has been demonstrated in a few different dielectric materials and lithographically fabricated structures. However, such localization is difficult to control, and requires strong magnetic fields or nonlinear optical effects, and electronic control has not been demonstrated. Here, we show control of optical Anderson localization using charge carriers injected into more than 100 submicrometre-scale p-n diodes. The diodes are embedded into the cross-section of the optical waveguide and are fabricated with a technology compatible with the current electronics industry. Large variations in the output signal, exceeding a factor of 100, were measured with 1 V and a control current of 1 mA. The transverse footprint of our device is only 0.125 µm(2), about five orders of magnitude smaller than optical two-dimensional lattices. Whereas all-electronic localization has a narrow usable bandwidth, electronically controlled optical localization can access more than a gigahertz of bandwidth and creates new possibilities for controlling localization at radiofrequencies, which can benefit applications such as random lasers, optical limiters, imagers, quantum optics and measurement devices.

Absence of Anderson Localization of Light in a Random Ensemble of Point Scatterers

As discovered by Philip Anderson in 1958, strong disorder can block propagation of waves and lead to the localization of wavelike excitations in space. Anderson localization of light is particularly exciting in view of its possible applications for random lasing or quantum information processing. We show that, surprisingly, Anderson localization of light cannot be achieved in a random three-dimensional ensemble of point scattering centers that is the simplest and widespread model to study the multiple scattering of waves. Localization is recovered if the vector character of light is neglected. This shows that, at least for point scatterers, the polarization of light plays an important role in the Anderson localization problem.

Anderson localization of light in the presence of weak longitudinal modulation of the refractive index in 1D disordered waveguide lattices

We report an enhancement of the effect of transverse localization of light (TL) in the presence of a weak longitudinal modulation of the refractive index in disordered waveguide lattices. In our chosen lattices, tunneling inhibition along the length favors diffraction-free propagation along with the simultaneous presence of transverse disorder. Our results will be useful for tuning the threshold value of disorder to achieve localized light.

Hybrid Bloch–Anderson localization of light

We investigate the interplay of Bloch oscillations and Anderson localization in optics. Gradual washing out of Bloch oscillations and the formation of nearly stationary averaged intensity distributions, which are symmetric for narrow and strongly asymmetric for broad input excitations, are observed experimentally in laser-written waveguide arrays. At large disorder levels Bloch oscillations are completely destroyed and both narrow and wide excitations lead to symmetric stationary averaged intensity distributions with exponentially decaying tails.

Defect-controlled transverse localization of light in disordered photonic lattices

We study numerically Anderson localization of light in a disordered photonic lattice containing vacancy defects of different length. The influence of Kerr nonlinearity and disorder level on the transverse localization of light in different triangular lattice geometries is discussed. We demonstrate both suppression and enhancement of light localization in the presence of defects of different size, depending on the disorder level and the strength of the nonlinearity. We find that, in the linear regime, localization is more pronounced in the lattice with the simplest defect type—the single vacancy. In a strongly focusing nonlinear regime, the presence of all defect kinds enhances localization, as compared to the case with no defects. In the defocusing nonlinear regime, a suppression of localization in the presence of all defect types is demonstrated, as compared to the localization in the lattice without defects. In the end, the effect of input beam width on various regimes of Anderson localization is discussed.

Anderson localization of light

The Anderson localization of light within disordered media has become a topic of great interest in recent years. Here the characterization of the effect and its related phenomena are reviewed, with a discussion on the role that nonlinearity and quantum correlated photons can play.

Anomalous Localization of Light in One-Dimensional Disordered Photonic Superlattices

The Anderson localization of light in one-dimensional disordered photonic superlattices is theoretically studied. The system is considered to be made of alternating dispersive and nondispersive layers of different randomthickness. Dispersive slabs of the heterostructure are characterized by Drude-like frequency-dependent electric permittivities and magnetic permeabilities. Numerical results for the localization length are obtained via an analytical model, only valid in the case of weak disorder, and also through its general definition involving the transmissivity of the multilayered system. Anomalous λ 4 - and λ -4 -dependencies of the localization length in positive-negative disordered photonic superlattices are obtained, in certain cases, in the long and short wavelength limits, respectively. PACS: 78.67.Pt; 42.25.-p; 46.65.+g; 72.15.Rn

Anderson localization of light in PT-symmetric optical lattices

Anderson localization (AL) of light is investigated numerically in a disordered parity-time (PT)-symmetric potential, in the form of an optical lattice. The lattice is recorded in a nonlinear medium with Kerr nonlinearity. We demonstrate enhancement of light localization in a PT-symmetric lattice, as compared to the localization in the corresponding real lattice. The effect of strength of the gain-loss component in the PT lattice on various regimes of AL is also discussed. It is found that the localization exists and is further enhanced above the threshold strength of the imaginary part of the potential. The influence of nonlinearity and disorder level on the transverse localization of light in such a complex-valued potential is addressed.

Propagation properties of a wave in a disordered multilayered system containing hyperbolic metamaterials

Electromagnetic wave propagation in one-dimensional disordered structures composed of hyperbolic metamaterials is theoretically investigated. We find that the disordered system can suppress Anderson localization of light at long-wavelength limit under a finite range of incident angle. For isolated frequencies and for specific angles of incidence, it only occurs at areas of Brewster anomaly. Within the zero-n¯ gap, structural disorder has little impact on the localization length. In contrast, the localization length increases with the increase of the degree of disorder in the Bragg gap, giving rise to enhanced transmission of light. At the vicinities of Bragg gap edge, the localization is suppressed (enhanced) evidently outside (inside) the gap. We also find that the increase of disorder or incidence angle can result in an increase of strength and range of resonances. The role of absorption in our disordered system is also discussed.

Influence of a medium’s nonlinearity on Anderson localization of light in optically induced photonic lattices

We studied numerically the Anderson localization of light in the two-dimensional square photonic lattice, optically induced in both linear and nonlinear dielectric media. We investigated the combined influence of nonlinearity and disorder on Anderson localization in bulk media, as well as when there is interface between the linear and nonlinear medium. In bulk, there exist strongly nonlinear regimes in which localization is less pronounced than in the linear regime. We found that in the defocusing nonlinear regime, the localization is always less pronounced than in the linear regime. We also studied surface-localized modes near the interface between linear and nonlinear dielectric media with an optically induced photonic lattice, and observed the threshold for their existence. We demonstrate suppression of the localization at the interface for lower disorder levels, compared with both pure linear and pure nonlinear media.

Anderson localization in metamaterials and other complex media (Review Article)

This is a review of some recent (mostly ours) results on Anderson localization of light and electron waves in complex disordered systems, including: (i) left-handed metamaterials, (ii) magnetoactive optical structures, (iii) graphene superlattices, and (iv) nonlinear dielectric media. First, we demonstrate that left-handed metamaterials can significantly suppress localization of light and lead to an anomalously enhanced transmission. This suppression is essential at the long-wavelength limit in the case of normal incidence, at specific angles of oblique incidence (Brewster anomaly), and in vicinity of zero-ɛ or zero-μ frequencies for dispersive metamaterials. Remarkably, in disordered samples comprised of alternating normal and left-handed metamaterials, the reciprocal Lyapunov exponent and reciprocal transmittance increment can differ from each other. Second, we study magnetoactive multilayered structures, which exhibit nonreciprocal localization of light depending on the direction of propagation and on polarization. At resonant frequencies or realizations such nonreciprocity results in effectively unidirectional transport of light. Third, we discuss the analogy between wave propagation through multilayered samples with metamaterials and charge transport in graphene, which provides a simple physical explanation of unusual conductive properties of disordered graphene superlatices. We predict disorder-induced resonance of the transmission coefficient at oblique incidence of Dirac quasiparticles. Finally, we demonstrate that an interplay of nonlinearity and disorder in dielectric media can lead to bistability of individual localized states excited inside the medium at resonant frequencies. This results in nonreciprocity of wave transmission and unidirectional transport of light.

Object-oriented electrodynamic S-matrix code with modern applications

The S-matrix algorithm for the propagation of an electromagnetic wave through planar stratified media has been implemented in a modern object-oriented programing language. This implementation is suitable for the study of such applications as the Anderson localization of light and super-resolution (perfect lensing). For our open-source code to be as useful as possible to the scientific community, we paid particular attention to the pathological cases that arise in the limit of vanishing absorption.

Nonlinear Photonic Structures

In photonics, the investigation of structured nonlinear systems is an active and vivid research area. Their ability to control the dispersion and diffraction properties of light allows tailoring light in its spectral, temporal, and spatial features. Manipulating the spatial features, i.e., overcoming diffraction, is an actual and challenging issue that is of utmost importance for further information processing tasks. With this contribution, we highlight some of the most recent publications in this field. Among others, we discuss the progress in complex photonic lattice generation as well as the guiding and control of discrete spatial solitons-entities that no longer spread during propagation. We also emphasize the importance of photonic lattices as optical analogies to quantum mechanical systems and review current results on Anderson localization of light.

Anderson localization of light at the interface between linear and nonlinear dielectric media with an optically induced photonic lattice

In a numerical study, we observe Anderson localization of surface modes at the interface between a linear and a nonlinear dielectric medium, containing an optically induced disordered photonic lattice. We discover the threshold for the existence of such localized modes. The influence of Kerr nonlinearity and disorder levels on the transverse localization of light at such an interface is discussed. We demonstrate the suppression of localization for lower disorder levels, as compared to both completely linear and completely nonlinear medium. We also reveal Anderson localization at the linear-nonlinear interface in the presence of a phase-slip defect, and demonstrate the suppression of localization in that case as well.

Lattice Boundaries and Dimensionality Crossover in Anderson Localization of Light

We have learned how to construct ordered index-of-refraction-modulated structures that allow us to control the propagation of light. Initially, researchers were simply interested in fabrication; now they are exploring limitations in the structures.

Transverse localization of light in nonlinear photonic lattices with dimensionality crossover

In a numerical study, we demonstrate the dimensionality crossover in Anderson localization of light. We consider crossover from the two-dimensional (2D) to the one-dimensional (1D) lattice, optically induced in both linear and nonlinear dielectric media. The joint influence of nonlinearity and disorder on Anderson localization in such systems is discussed in some detail. We find that, in the linear regime, the localization is more pronounced in two dimensions than in one dimension. We also find that the localization in the intermediate cases of crossover is less pronounced than in both the pure 1D and 2D cases in the linear regime, whereas in the nonlinear regime this depends on the strength of the nonlinearity. There exist strongly nonlinear regimes in which 1D localization is more pronounced than the 2D localization, opposite to the case of the linear regime. We find that the dimensionality crossover is characterized by two different localization lengths, whose behavior is different along different transverse directions.

Disorder-induced localization of light near edges of nonlinear photonic lattices

We investigated the influence of edges and corners on the Anderson localization of light in disordered two-dimensional photonic lattices that are optically induced in nonlinear saturable photorefractive media. A systematic quantitative study of gradual transition from corner to bulk Anderson localization in truncated two-dimensional photonic lattices was carried out. We analyzed numerically the localization at several corners and edges of the square and triangular photonic lattices and compared them with the localization in bulk medium. We found that, for strong disorder, corners and edges effectively suppress Anderson localization, as compared to the bulk, but to a varying degree.

Anomalous retroreflection from strongly absorbing nanoporous semiconductors

Pronounced retroreflection behavior is reported for a fishnet nanoporous strongly absorbing semiconductor material. Retroreflection features a half-cone about 0.35 rad along with diffusive specular reflection for all angles of incidence. Retroreflection is apparent by the naked eye with daylight illumination and exhibits no selectivity with respect to wavelength and polarization of incident light featuring minor depolarization of retroreflected light. The reflectance in the backward direction measures 12% with respect to a white scattering etalon. The phenomenon can be classified neither as coherent backscattering nor as Anderson localization of light. The primary model includes light scattering from strongly absorptive and refractive superwavelength clusters existing within the porous fishnet structure. A reasonable qualitative explanation is based on the fact that strict retroreflection obeys shorter paths inside absorbing medium, whereas all alternative paths will lead to stronger absorption of light.

Self-induced transparency and the Anderson localization of light

Self-induced transparency pulses propagating in a random medium embedded in a two-level system can transfer energy to localized Anderson states. This allows the onset of two-level laserlike action.