arXiv subjects

A. A. Chabanov

Publications and source records attributed to A. A. Chabanov.

At least 19 recordsLinked to original sources

arXiv2023

Optical Limiter Based on PT-Symmetry Breaking of Reflectionless Modes

The application of parity-time (PT) symmetry in optics, especially PT-symmetry breaking, has attracted considerable attention as a novel approach to controlling light propagation. Here, we report optical limiting by two coupled optical cavities with a PT-symmetric spectrum of reflectionless modes. The optical limiting is related to broken PT symmetry due to light-induced changes in one of the cavities. Our experimental implementation is a three-mirror resonator of alternating layers of ZnS and cryolite with a PT-symmetric spectral degeneracy of two reflectionless modes. The optical limiting is demonstrated by measurements of single 532-nm 6-ns laser pulses. At fluences below 10 mJ/cm2, the multilayer exhibits a flat-top passband at 532 nm. At higher fluences, laser heating combined with the thermo-optic effect in ZnS leads to cavity detuning and PT-symmetry breaking of the reflectionless modes. As a result, the entire multilayer structure quickly becomes highly reflective, protecting itself from laser-induced damage. The cavity detuning mechanism can differ at much higher limiting thresholds and include nonlinearity.

physics.optics↗

arXiv2019

Free-Space Wide-Aperture Sheet-Isolator Based on a Multilayered Resonant Cavity

We introduce the first conceptual design of a free-space thin-sheet isolator with unlimited aperture and the possibility of a broadband omnidirectional rejection of the backward propagating light. The proposed design involves a multilayered resonant cavity incorporating subwavelength magnetic layers, dichroic nanolayers, and an optional metallic nanolayer. The cavity resonance enhances the Faraday rotation produced by the subwavelength magnetic layers, while providing nearly total absorption of the backward-propagating light by the dichroic nanolayers. The latter is a necessary and the most challenging condition for a thin-sheet isolator with unlimited aperture to function. The (optional) metallic nanolayer provides rejection of the obliquely incident light, which otherwise would be partially transmitted in either direction. Our numerical simulations and quasi-optical measurements at millimeter-wave frequencies illustrate how the key elements of the layered-sheet isolator work. Our approach can be scaled down to long- and mid-infrared wavelengths.

physics.app-ph↗

arXiv2019

Light-induced optical switching in an asymmetric metal-dielectric microcavity with phase-change material

We propose an infrared power switch based on an asymmetric high-Q microcavity incorporating a metallic nanolayer in close proximity to a layer made of a phase-change material (PCM). The microcavity is designed so that when the PCM layer is in the low-temperature phase, the metallic nanolayer coincides with a nodal plane of the resonant electric field component, to allow a high resonant transmittance. As the light intensity exceeds a certain threshold, light-induced heating of the PCM layer triggers the phase transition accompanied by an abrupt change in its refractive index in the vicinity of the transition temperature. The latter results in a shift of the nodal plane away from the metallic nanolayer, rendering the entire microcavity highly reflective over a broad frequency range. The nearly binary nature of the PCM refractive index allows for the low-intensity resonant transmission over a broad range of ambient temperatures below the transition point.

physics.optics↗

arXiv2014

The Single-Channel Regime of Transport through Random Media

The propagation of light through samples with random inhomogeneities can be described by way of transmission eigenchannels, which connect incoming and outgoing external propagating modes. Although the detailed structure of a disordered sample can generally not be fully specified, these transmission eigenchannels can nonetheless be successfully controlled and utilized for focusing and imaging light through random media. Here we demonstrate that in deeply localized quasi-1D systems, the single dominant transmission eigenchannel is formed by an individual Anderson localized mode or by a "necklace state". In this single-channel regime, the disordered sample can be treated as an effective 1D system with a renormalized localization length, coupled through all the external modes to its surroundings. Using statistical criteria of the single-channel regime and pulsed excitations of the disordered samples allows us to identify long-lived localized modes and short-lived necklace states at long and short time delays, respectively.

cond-mat.dis-nn↗

arXiv2011

Dynamics of Fluctuations of Localized Waves

We follow the temporal evolution of mesoscopic intensity fluctuations and correlation in strongly localized samples. We find an initial burst in relative transmission fluctuations in random one dimensional (1D) samples due to fluctuations in the arrival time of ballistic transmission. Relative fluctuations subsequently rise, then drop to a minimum at a time t_m, after which they increase rapidly in 1D simulations and quasi-1D (Q1D) measurements. For t > 3t_m, results in 1D and Q1D samples converge towards predictions of a dynamic single parameter scaling model. These results reflect the changing number of modes participating appreciably in transmission as the impact of longer lived modes grows with time delay.

cond-mat.dis-nn↗

arXiv2009

Nonuniversal dynamic conductance fluctuations in disordered systems

Sample-to-sample fluctuations of the time-dependent conductance of a system with static disorder have been studied by means of diagrammatic theory and microwave pulsed transmission measurements. The fluctuations of time-dependent conductance are not universal, i.e., depend on sample parameters, in contrast to the universal conductance fluctuations in the steady-state regime. The variance of normalized conductance, determined by the infinite-range intensity correlation C_3(t), is found to increase as a third power of delay time from an exciting pulse, t. C_3(t) grows larger than the long-range intensity correlation C_2(t) after a time t_q ~ ^{1/2} t_D (t_D being the diffusion time, being the average dimensionless conductance).

cond-mat.mes-hall↗

arXiv2009

Intensity Statistics of Random Signals in Gaussian Noise

The intensity statistics of signals in the presence of Gaussian noise is obtained by studying the model of a random signal plus a random phasor sum. The additive Gaussian noise is shown to result in a Bessel transform of the probability density of the signal intensity. The transformation of the intensity statistics can generally be applied to a mixture of independent random signals, one of which being a complex-valued Gaussian random process. It is used to retrieve intensity statistics of microwave pulsed transmission from Gaussian noise at long time delays.

cond-mat.dis-nn↗

arXiv2008

Dynamics of Localized Waves

We have measured pulsed microwave transmission through quasi-1D samples with lengths up to three localization lengths. For times approaching four times the diffusion time τ_D, transmission is diffusive in accord with the self-consistent theory of localization for the renormalized diffusion coefficient in space and frequency, D(z,Ω). For longer times, the transmission decay rate first agrees with and later falls increasingly below the self-consistent theory. Beyond the Heisenberg time, the decay rate approaches the predictions of a dynamic single parameter scaling model which reflects the decay of long-lived localized modes and converges to the results of 1D simulations.

cond-mat.dis-nn↗

arXiv2007

Strongly Resonant Transmission of Electromagnetic Radiation in Periodic Anisotropic Layered Media

The electromagnetic dispersion in periodic layered media can be tailored and their resonant properties can be considerably improved by utilizing anisotropic materials. Periodic structures with a photonic band edge split into two parts, or so-called split band edge, exhibit superior resonant properties including exceptionally high Q-values of transmission resonances and nearly perfect impedance matching at the boundaries, even when the number of unit cells N is not large. A microwave transmission resonance with Q~220 is demonstrated in a periodic stack of form-birefringent layers with N=12 realized in a waveguide geometry.

physics.optics↗

arXiv2006

Random lasing in weakly scattering systems

We present detailed experimental and numerical studies of random lasing in weakly scattering systems. The interference of scattered light, which is weak in the passive systems, is greatly enhanced in the presence of high gain, providing coherent and resonant feedback for lasing. The lasing modes are confined in the vicinity of the pumped volume due to absorption of emitted light outside it. In the ballistic regime where the size of gain volume is less than the scattering mean free path, lasing oscillation occurs along the direction in which the gain volume is most extended, producing directional laser output. The feedback for lasing originates mainly from backscattering of particles near the boundaries of pumped region. It results in nearly constant frequency spacing of lasing modes, which scales inversely with the maximum dimension of the gain volume.

physics.optics↗

arXiv2005

Signatures of photon localization

Signatures of photon localization are observed in a constellation of transport phenomena which reflect the transition from diffusive to localized waves. The dimensionless conductance, g, and the ratio of the typical spectral width and spacing of quasimodes, δ, are key indicators of electronic and classical wave localization when inelastic processes are absent. However, these can no longer serve as localization parameters in absorbing samples since the affect of absorption depends upon the length of the trajectories of partial waves traversing the sample, which are superposed to create the scattered field. A robust determination of localization in the presence of absorption is found, however, in steady-state measurements of the statistics of radiation transmitted through random samples. This is captured in a single parameter, the variance of the total transmission normalized to its ensemble average value, which is equal to the degree of intensity correlation of the transmitted wave, κ. The intertwined effects of localization and absorption can also be disentangled in the time domain since all waves emerging from the sample at a fixed time delay from an exciting pulse, t, are suppressed equally by absorption. As a result, the relative weights of partial waves emerging from the sample, and hence the statistics of intensity fluctuations and correlation, and the suppression of propagation by weak localization are not changed by absorption, and manifest the growing impact of weak localization with t.

cond-mat.dis-nn↗

arXiv2005

Statistics of the Mesoscopic Field

We find in measurements of microwave transmission through quasi-1D dielectric samples for both diffusive and localized waves that the field normalized by the square root of the spatially averaged flux in a given sample configuration is a Gaussian random process with position, polarization, frequency, and time. As a result, the probability distribution of the field in the random ensemble is a mixture of Gaussian functions weighted by the distribution of total transmission, while its correlation function is a product of correlators of the Gaussian field and the square root of the total transmission.

cond-mat.dis-nn↗

arXiv2004

Dynamic Correlation in Wave Propagation in Random Media

We report time-resolved measurements of the statistics of pulsed transmission through quasi-one-dimensional dielectric media with static disorder. The normalized intensity correlation function with displacement and polarization rotation for an incident pulse of linewidth $σ$ at delay time t is a function only of the field correlation function, which is identical to that found for steady-state excitation, and of $κ_σ(t)$, the residual degree of intensity correlation at points at which the field correlation function vanishes. The dynamic probability distribution of normalized intensity depends only upon $κ_σ(t)$. Steady-state statistics are recovered in the limit $σ$->0, in which $κ_{σ=0}$ is the steady-state degree of correlation.

cond-mat.dis-nn↗

arXiv2003

Elimination of cracks in self-assembled photonic band gap crystals

Thin colloidal crystals (or synthetic opals) composed of Stober silica spheres typically develop cracks when they are utilized to obtain photonic band gap crystals (or inverted opals). We find that by sintering the silica spheres prior to assembly of the opal these cracks can be avoided. We report the effects of temperature and duration of the heat treatment on 850 nm silica spheres using electron microscopy, thermogravimetry, and light scattering. We also find a large dependence of the refractive index of the silica on the temperature of the heat treatment. This may allow tuning of the refractive index of silica spheres.

cond-mat.mtrl-sci↗

arXiv2003

Impact of weak localization in the time domain

We find a renormalized "time-dependent diffusion coefficient", D(t), for pulsed excitation of a nominally diffusive sample by solving the Bethe-Salpeter equation with recurrent scattering. We observe a crossover in dynamics in the transformation from a quasi-1D to a slab geometry implemented by varying the ratio of the radius, R, of the cylindrical sample with reflecting walls and the sample length, L. Immediately after the peak of the transmitted pulse, D(t) falls linearly with a nonuniversal slope that approaches an asymptotic value for R/L >> 1. The value of D(t) extrapolated to t = 0 depends only upon the dimensionless conductance, g, for R/L << l 1 and only upon kl for R/L >> 1, where k is the wave vector and l is the bare mean free path.

cond-mat.dis-nn↗

arXiv2003

Mesoscopic Correlation with Polarization of Electromagnetic Waves

Mesoscopic correlations are observed in the polarization of microwave radiation transmitted through a random waveguide. These measurements, supported by diagrammatic theory, permit the unambiguous identification of short, long, and infinite range components in the intensity correlation function, as well as an additional frequency-independent component.

cond-mat.dis-nn↗

arXiv2003

Breakdown of Diffusion in Dynamics of Extended Waves in Mesoscopic Media

We report the observation of nonexponential decay of pulsed microwave transmission through quasi-one-dimensional random dielectric media that signals the breakdown of the diffusion model of transport for temporally coherent extended waves. The decay rate of transmission falls nearly linearly in time due to a nearly gaussian distribution of the coupling strengths of quasi-normal electromagnetic modes to free space at the sample surfaces. The peak and width of this distribution scale as L^{-2.05} and L^{-1.81}, respectively.

cond-mat.dis-nn↗

arXiv2001

Statistics of Dynamics of Localized Waves

The measured distribution of the single-channel delay time of localized microwave radiation and its correlation with intensity differ sharply from the behavior of diffusive waves. The delay time is found to increase with intensity, while its variance is inversely proportional to the fourth root of the intensity. The distribution of the delay time weighted by the intensity is found to be a double-sided stretched exponential to the 1/3 power centered at zero. The correlation between dwell time and intensity provides a dynamical test of photon localization.

cond-mat.dis-nn↗