S. E. Skipetrov

Localization of ultrasound in a three-dimensional elastic network

A systematic study of the propagation of ultrasound through a random network of aluminium beads provides the first demonstration of the Anderson localization of classical waves in a 3D system.

Wave scattering in complex media : from theory to applications

Light Transport in Complex Photonic Systems.- Propagation of Light in Strongly Disordered Photonic Materials and Random Lasers.- Weak Localisation of Light by Atoms with Quantum Internal Structure.- Light Propagation in Chiral and Magnetochiral Random Media.- Diffuse Waves in Nonlinear Disordered Media.- Coherent Effects in the Multiple Scattering of Light in Random Media.- Mesoscopic Dynamics.- Diffusing Acoustic Wave Spectroscopy: Field Fluctuation Spectroscopy with Multiply Scattered Ultrasonic Waves.- Intensity Correlations and Fluctuations of Waves Transmitted through Random Media.- Spectral Coherence of Wave Fields in Random Media.- Photon Localization in Resonant Media.- Anderson Localization of Electromagnetic Waves in Confined Disordered Dielectric Media.- Laser Action in the Regime of Strong Localization.- Statistics of Reflected Speckle Intensities Arising from Localized States Inside the Gap of Disordered Photonic Crystals.- Auto-Focalisation, Communication and Sonoluminescence with Acoustic Time Reversal.- 3D Phononic Crystals.- Left-Handed Materials.- Negative Index Complex Metamaterials.- Local Field Statistics and Plasmon Localization in Random Metal-Dielectric Films.- Radiative Transfer Theory: From Maxwells Equations to Practical Applications.- Transfer of Trapped Electromagnetic Radiation in an Ensemble of Resonant Mesoscopic Scatterers.- Boundary Conditions in Radiative Transfer.- Radiation Transfer in Nematic Liquid Crystals.- Dynamic Light Scattering in Confined Liquid Crystals.- Optical Properties and Fluctuations in Liquid Crystals with One-Dimensional Large-Scale Periodicity.- Light Scattering in a Disperse Layer with Partially Ordered Soft Particles.- Optical Microrheology of Soft Complex Materials.- Coherent Opposition Effect for Discrete Random Media.- Scattering of SH waves in Media with Cracks and Elastic Inclusions.- Digital Communication with Time-Reversal in a Multiple Scattering Medium.- Wireless Propagation of Optical Coded Pulse Streams through Turbid Media.- Elastic Light Scattering by Dielectric Microspheres for C-Band Applications.

Imaging of dynamic heterogeneities in multiple-scattering media

A new method of visualizing objects with distinct internal dynamics of the constituent scattering particles embedded in a liquid multiple-scattering medium is presented. We report dynamic multiple-light-scattering experiments and a theoretical model, based on diffusing photon-density waves for concentrated colloidal suspensions in Brownian motion, as a background medium into which is inserted a capillary containing (i) the same suspension under flow, or (ii) suspensions of different particle sizes in Brownian motion. These model objects, with purely dynamic but no static scattering contrast, can be visualized by space-resolved measurements of the time autocorrelation function g2(t) of the scattered light intensity at the sample surface. Maximum contrast occurs at a parameter-dependent finite correlation time t. The physical origin of this effect is outlined. Our data are in excellent quantitative agreement with the model, with no adjustable parameter.

Nonlinear optics: Disorder is the new order

Pure, perfectly regular crystals were believed to be essential for the efficient operation of nonlinear optical devices. Surprisingly, it now seems that disordered materials might actually perform better.

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.

Dynamics of anderson localization in open 3D media

We develop a self-consistent theoretical approach to the dynamics of Anderson localization in open three-dimensional (3D) disordered media. The approach allows us to study time-dependent transmission and reflection, and the distribution of decay rates of quasimodes of 3D disordered slabs near the Anderson mobility edge.

Attojoule Calorimetry of Mesoscopic Superconducting Loops

We report the first experimental evidence of nontrivial thermal behavior of the simplest mesoscopic system--a superconducting loop. By measuring the specific heat C of an array of 450,000 noninteracting aluminum loops with very high accuracy of approximately 20 fJ/K, we show that the loops go through a periodic sequence of phase transitions (with a period of an integer number of magnetic flux quanta) as the magnetic flux threading each loop is increased. The transitions are well described by the Ginzburg-Landau theory and are accompanied by discontinuities of C of only several thousands of Boltzmann constants kB.

Observation of Spatial Fluctuations of the Local Density of States in Random Photonic Media

We experimentally study spatial fluctuations of the local density of states (LDOS) inside three-dimensional random photonic media. The LDOS is probed at many positions inside random photonic media by measuring emission rates of a large number of individual fluorescent nanospheres. The emission rates are observed to fluctuate spatially, and the variance of the fluctuations increases with the scattering strength. The measured variance of the emission rates agrees well with a model that takes into account the effect of the nearest scatterer only.

Noise in laser speckle correlation and imaging techniques

We study the noise of the intensity variance and of the intensity correlation and structure functions measured in light scattering from a random medium in the case when these quantities are obtained by averaging over a finite number N of pixels of a digital camera. We show that the noise scales as 1/N in all cases and that it is sensitive to correlations of signals corresponding to adjacent pixels as well as to the effective time averaging (due to the finite integration time) and spatial averaging (due to the finite pixel size). Our results provide a guide to estimation of noise levels in such applications as multi-speckle dynamic light scattering, time-resolved correlation spectroscopy, speckle visibility spectroscopy, laser speckle imaging etc.

Diffusing-wave spectroscopy from head-like tissue phantoms: influence of a non-scattering layer

We investigate the influence of a non-scattering layer on the temporal field autocorrelation function of multiple scattered light from a multilayer turbid medium such as the human head. Data from Monte Carlo simulations show very good agreement with the predictions of the correlation-diffusion equation with boundary conditions taking into account non-diffusive light transport within the non-scattering layer. Field autocorrelation functions measured at the surface of a multilayer phantom including a non-scattering layer agree well with theory and simulations when the source-receiver distance is significantly larger than the depth and the thickness of the non-scattering layer. Our results show that for source-receiver distances large enough to probe the dynamics in the human cortex, the cortical diffusion coefficient obtained by analyzing field autocorrelation functions neglecting the presence of the non-scattering cerebrospinal fluid layer is underestimated by about~