No abstract

Propagation of a coherent light through an anisotropic random medium generates randomly polarized field, known as polarization speckle. In this paper, an experimental technique is proposed and demonstrated to recover the transmittance of a polarized object from polarization speckle. Recovery of the polarized object from polarization speckle is made possible by combining the far-field intensity correlation of the object speckle with off-axis holography to determine the complex coherence function of the speckle. The desired object speckle which is uniformly polarized is filtered from the polarization speckle using a polarizer. The results are compared with the case where the complex coherence function is determined in the absence of the polarizer.

We present what we believe to be the first experimental demonstration of anomalous spectral behavior such as spectral shifts and spectral switches due to temporal correlation around the intensity minima in a white-light interferometer. Unusual behavior in the number of spectral fringes, measured within the source bandwidth, as a function of path delay between the interfering beams is also reported. Experimental observations match well with the spectra calculated by using the interference law in the spectral domain.

A pair of stable noncanonical scalar vortices of the same charge is generated experimentally across the cross section of an optical beam using a computer-generated hologram with higher-order fractional screw dislocation. The noncanonical nature of the generated vortices is identified by the gradient of the phase around each vortex and also the crossing angle between the zero contours of the real and imaginary parts of the optical field. The anisotropy of the vortices is controlled by the fractional order of the computer-generated hologram. The behavior of the rate of change of phase around each individual vortex is found to be different from that of the earlier reports on noncanonical vortices. The observed experimental results are qualitatively explained based on the effect of nonlocalized phases of the generated vortices. The generated beams with a nested pair of noncanonical vortices can be of importance in accelerated rotation of the beams and in optical micromanipulation.

Optical vortex beams with fractional topological charges (TCs) are generated by the diffraction of a Gaussian beam using computer generated holograms embedded with mixed screw-edge dislocations. When the input Gaussian beam has a finite wave-front curvature, the generated fractional vortex beams show distinct topological transformations in comparison to the integer charge optical vortices. The topological transformations at different fractional TCs are investigated through the birth and evolution of the points of phase singularity, the azimuthal momentum transformation, occurrence of critical points in the transverse momentum and the vorticity around the singular points. This study is helpful to achieve better control in optical micro-manipulation applications.