Scattering of low coherence radiation and applications

In an effort to understand complex scattering phenomena, characteristics of optical waves such as polarization, angular spectrum, and temporal coherence have been extensively studied. In this article we will review several applications where the coherence properties of broad-band radiation offer unique sensing and diagnostic capabilities

Near-field characterization of effective optical interfaces

The properties of many heterogeneous media depend on both the surface roughness and the local variations of the optical properties. An effective optical interface is usually invoked to describe the characteristics of such media. Using approaches specific to near-field optics, the two influences can be decoupled and a quantitative assessment of their contributions can be performed. It is also shown that a discrete random-walk model can be used to determine the magnitude of the dielectric constant fluctuations at subwavelength scales which, in turn, describe the morphology of optically inhomogeneous media

Stochastic sensing of relative anisotropic polarizabilities

We describe the concept of stochastic scattering polarimetry. This method allows determination of the anisotropic polarizability of a scattering object using a statistical analysis of the polarimetrically measured intensity distributions in the wave zone (far field). We show that this anisotropic polarizability may be determined even in situations where the state of polarization of the incident field is not known. The efficiency of the recovering procedure is demonstrated by several examples of light scattering in both far- and near-field geometries

Coupled dipole method for modeling optical properties of large-scale random media

We present an extension of the coupled dipole approximation technique to model optical properties of large-scale slabs of homogeneous and inhomogeneous materials. This method is based on a modification of the Green\u27s function to take into account the interaction between dipoles located at arbitrary distances within the slab. This method allows modeling of various aspects of the structural morphology of composite materials, including component size and spatial distribution as well as surface roughness effects. Our procedure provides an adequate description of far-field optical properties such as the specular and diffuse reflection of light

Generation of complete coherence in Young's interference experiment with random mutually uncorrelated electromagnetic beams

The recently developed theory that unifies the treatments of polarization and coherence of random electro-magnetic beams is applied to study field correlations in Young's interference experiment. It is found that at certain pairs of points the transmitted field is spatially fully coherent, irrespective of the state of coherence and polarization of the field that is incident on the two pinholes. © 2005 Optical Society of America

Poynting vector, energy density and energy velocity in anomalous dispersion medium

The Poynting vector, energy density and energy velocity of light pulses propagating in anomalous dispersion medium (used in WKD-like experiments) are calculated. Results show that a negative energy density in the medium propagates along opposite of incident direction with such a velocity similar to the negative group velocity while the direction of the Poynting vector is positive. In other words, one might say that a positive energy density in the medium would propagate along the positive direction with a speed having approximately the absolute valueof the group velocity. We further point out that neither energy velocity nor group velocity is a good concept to describe the propagation process of light pulse inside the medium in WKD experiment owing to the strong accumulation and dissipation effects.Comment: 6 page

Signal velocity, causality, and quantum noise in superluminal light pulse propagation

We consider pulse propagation in a linear anomalously dispersive medium where the group velocity exceeds the speed of light in vacuum (c) or even becomes negative. A signal velocity is defined operationally based on the optical signal-to-noise ratio, and is computed for cases appropriate to the recent experiment where such a negative group velocity was observed. It is found that quantum fluctuations limit the signal velocity to values less than c.Comment: 4 Journal pages, 3 figure

Self-healing properties of optical Airy beams

We investigate both theoretically and experimentally the self-healing properties of accelerating Airy beams. We show that this class of waves tends to reform during propagation in spite of the severity of the imposed perturbations. In all occasions the reconstruction of these beams is interpreted through their internal transverse power flow. The robustness of these optical beams in scattering and turbulent environments is also studied experimentally. Our observations are in excellent agreement with numerical simulations

Complex degree of mutual polarization in randomly scattered fields

Random electromagnetic fields resulting from light-matter interaction have strong intensity fluctuations and are characterized by various statistical parameters. The local polarization of these fields can also vary randomly leading to different degrees of global depolarization. Here we demonstrate that the spatial variability of the vectorial properties contains information about the origins of randomly scattered fields. In particular, we show that the complex degree of mutual polarization provides the high-order polarization correlations necessary to identify the sources of different random fields. Scattered fields with similar global properties but different origins can be efficiently discriminated from one single realization of the light-matter interaction

Pulsed light beams in vacuum with superluminal and negative group velocities

Gouy's phase of transversally limited pulses can create a strong anomalous dispersion in vacuum leading to highly superluminal and negative group velocities. As a consequence, a focusing pulse can diverge beyond the focus before converging into it. A simple experiment is proposed.Comment: 4 pages, 5 figure