Serkan Sahin

Light sources generating far fields with tunable flat profiles

Planar, scalar, optical Schell-model, and quasi-homogeneous sources with correlations that are Fourier transforms of multi-Gaussian functions are introduced. It is demonstrated that far fields produced by these families of sources carry interesting characteristics, being flatlike with adjustable steepness of the edge. Beam conditions for such sources are also derived.

Multi-Gaussian Schell-model beams

In a recent publication [Opt. Lett.37, 2970 (2012)10.1364/OL.37.002970], a novel class of planar stochastic sources, generating far fields with flat intensity profiles, was introduced. In this paper we examine the behavior of the spectral density and the state of coherence of beamlike fields generated by such sources on propagation in free space and linear isotropic random media. In particular, we find that at sufficiently large distances from the source, the medium destroys the flat intensity profile, even if it remains such for intermediate distances from the source.

Effect of the pair-structure factor of a particulate medium on scalar wave scattering in the first Born approximation.

Using scattering matrices and the angular spectrum representation of waves, we develop the analytical theory of scattering of random scalar waves from random collections of particles, valid under the first Born approximation. We demonstrate that in the calculation of far-field statistics, such as the spectral density and the spectral degree of coherence, the knowledge of the pair-structure factor of the collection is crucial. We illustrate our analytical approach by considering a numerical example involving scattering of two partially correlated plane waves from a random distribution of spheres.

Scattering of light from particles with semisoft boundaries

A three-dimensional multi-Gaussian function, being a finite sum of Gaussian functions, is adopted for modeling of a spherically symmetric scatterer with a semisoft boundary, i.e. such that has continuous and adjustable drop in the index of refraction. A Gaussian sphere and a hard sphere are the two limiting cases when the number of terms in multi-Gaussian distribution is one and infinity, respectively. The effect of the boundarys softness on the intensity distribution of the scattered wave is revealed. The generalization of the model to random scatterers with semisoft boundaries is also outlined.

Free-space propagation of the spectral degree of cross-polarization of stochastic electromagnetic beams

Based on the unified theory of coherence and polarization and the extended Huygens–Fresnel integral the free-space evolution of the recently introduced spectral degree of cross-polarization of a stochastic electromagnetic beam is studied. Unlike the spectral degree of coherence, the degree of cross-polarization is unbounded and exhibits non-monotonic changes with growing propagation distance and growing radial distance from the center of the beam, at fixed transverse cross-sections. Our numerical results pertain to the electromagnetic Gaussian Schell-model beams. We derive expressions for the cross-spectral density matrix of the EGSM beam for arbitrary transverse and longitudinal positions. The results show that the behavior of the degree of cross-polarization on propagation is determined by all of the parameters of the source radiating the beam. At sufficiently large distances from the source, the degree of cross-polarization stabilizes for all points within the beam independently of their radial positions.

Light scattering by three-dimensional objects with semi-hard boundaries.

We introduce analytical models for scattering potentials of particles that have ellipsoid-, cylinder-, and parallelepiped-like shapes and adjustable edge sharpness with the help of the three-dimensional versions of the multi-Gaussian functions. The far fields produced upon scattering from such potentials are examined in detail and are shown to qualitatively and quantitatively depend on the scatterers symmetry type as well as its orientation and edge sharpness.

Crystalline human eye lens’ response to stochastic light

We present the first account (to our knowledge) of interaction between stochastic light and the crystalline human eye lens. In particular, the spectral density and the spectral degree of polarization of light focused by the crystalline lens onto the eyes back wall are examined. We find that the correlation properties of the incident light play the important role in the process of image formation by the eye and in its perception of polarization features of the incoming radiation.

Fluctuations in the instantaneous Stokes parameters of stochastic electromagnetic beams propagating in the turbulent atmosphere

Fluctuations in Stokes parameters of stochastic electromagnetic beams on propagation in turbulent atmosphere are studied. The expressions are derived for the scintillation indexes (contrasts) of the Stokes parameters and their versions normalized by the instantaneous intensity in the case when the beam is generated by the electromagnetic Gaussian Schell-model source with uniform polarization. We illustrate our analytical results by numerical examples.

Generalized Stokes parameters in phase space

The generalized Stokes parameters (GSP) are studied under the theory of phase space. It is noted that phase-space Stokes parameters can be a useful tool for Wigner distribution function measurements. Electromagnetic Wigner functions are introduced by use of the two-point statistics of GSP. The advantage in the GSP is that they can be measured in terms of the electric correlation matrix (which is a measurable quantity) or they can be measured independently. Hence, the GSP help in finding the polarization and coherence properties of electromagnetic beams. Within this framework, by using the GSP in phase space, the intensity feature of electromagnetic beams in phase space is given, as well.

Light Scattering from Deterministic and Random Media with Semi-Soft Boundaries

A three-dimensional multi-Gaussian function is adopted for modeling of a spherically-symmetric scatterer with semi-soft boundary, i.e. such that has continuous and adjustable drop in the index of refraction.