Chaim Schwartz

Conservation of angular momentum of light in single scattering.

In this paper we discuss the conservation of angular momentum of light in single scattering of circularly polarized light from a spherical, non-absorbing particle. We show that the angular momentum carried by the incident wave is distributed in the scattered waves between terms related to polarization or spin and to orbital angular momentum, respectively. We also show that, in all scattering directions, a constant ratio exists between the flux density of the total angular momentum and the intensity.

Backscattered polarization patterns determined by conservation of angular momentum.

It is demonstrated that the occurence of backscattered polarization patterns relates to the conservation of angular momentum of light. Using the geometrical phase formalism in the spin space, we develop a model where the helicity-maintaining and the helicity-flipping multiple-scattering processes can be accounted for. The model explains practically all the symmetries present in the spatially resolved Mueller matrices.

Backscattered polarization patterns, optical vortices, and the angular momentum of light

We demonstrate that the polarization patterns observed in backscattering of linearly polarized light are a manifestation of the conservation of angular momentum of light. We will show that this phenomenon can be described in terms of phase vortices that are acquired by the right and left circularly polarized components. The helicity and orbital angular momentum of these components satisfy the requirement for conservation of angular momentum.

Enhanced backscattering of optical vortex fields

The effect of an incident field with a phase screw dislocation (a so-called optical vortex) on the shape of the enhanced backscattering cone was studied theoretically and demonstrated experimentally. We show that the correlation function of the incident field acts as a filter that modifies the shape of the enhanced backscattering cone. The peak value is reduced, and its width is increased as the topological charge of the phase dislocation increases.

Mode coupling approach to beam propagation in atmospheric turbulence

A mode coupling approach based on the modal theory of coherence is suggested for the study of partially coherent beams in atmospheric turbulence. An approximate expression is derived for the mode power coupling coefficients, and some specific cases are studied using numerical methods. Several general results derived from the properties of the coupling coefficients are also presented.

Probing Random Media with Singular Beams

Optical fields containing phase singularities provide additional capabilities in studying random media. Coherent backscattering of such fields will be thoroughly discussed for the case of both double-pass geometries and volume scattering random media.

Polarization patterns and symmetries as a manifestation of helicity preserving characteristics of scattering media

Polarization patterns which are observed in backscattering from random media are shown to be connected with the helicity preserving characteristics of the scattering particles. The properties of the spatially resolved Mueller matrix can be derived in a simple manner and it is shown that they are related to scattering trajectories that preserve the total angular momentum of light.

Inverse source problem for partially polarized beams in turbulent media

The propagation of a class of partially polarized beams though atmospheric turbulence is treated using the coherent-modes-decomposition approach. This approach allows specifying the properties of sources generating radiation with a narrow polarization distribution that could be employed in active polarimetric remote sensing applications.

Measuring the Diffusion Coefficient Independent of the Boundary Conditions

We present an experimental method of non-invasively measuring the optical pathlength distribution in diffusive media using dual-fiber interferometry, which allows for the evaluation of the diffusion coefficient independent of the boundary conditions.

Enhanced backscattering of vortex fields

The effect of using an illumination beam with a phase screw dislocation (a so called optical vortex beam) on filtering the path lengths contributions to enhanced backscattering from random media was studied theoretically and demonstrated experimentally.