Bhaskar Kanseri

Experimental determination of electric cross-spectral density matrix and generalized Stokes parameters for a laser beam

We report an experimental method to determine the elements of the electric cross-spectral density matrix for laser light. For this purpose an additional setup consisting of mirrors and reflecting prisms is utilized with the conventional Youngs interferometer to overcome existing experimental limitations. The generalized Stokes parameters, which are the characteristics of two spatial points of the electromagnetic field, are also obtained for a pair of points. The knowledge of these two quantities might be useful in determining the change in polarization properties of light in propagation and their effects in optical measurements.

Direct determination of the generalized Stokes parameters from the usual Stokes parameters

We report an experimental method to determine the generalized Stokes parameters for a pair of points in the cross section of an electromagnetic beam, e.g., an expanded laser beam, with the help of a Youngs interferometer and a set of polarizers and quarter-wave plates. The method is investigated theoretically using the electromagnetic spectral interference law. The generalized Stokes parameters, owing to their two-point nature, determine the behavior of the single-point polarization properties of the electromagnetic beam at a field point. The present method offers a unique means to determine the two-point parameters (correlation functions) by measuring the usual Stokes parameters (intensities) and the contrast parameters (visibilities) of the beam. The method might be applicable to determine the polarization dependent changes in various optical measurements.

Observation of the Fresnel and Arago laws using the Mach-Zehnder interferometer

An experimental study is conducted to determine the effect of polarization on the interference of light waves. By using the temporal coherence property of light in a Mach-Zehnder interferometer, we verified the four important Fresnel and Arago laws for linearly polarized and circularly polarized light. This experiment provides a simple method for undergraduates to study the phenomena of interference and polarization.

Three-dimensional quantum polarization tomography of macroscopic Bell states

The polarization properties of macroscopic Bell states are characterized using three-dimensional quantum polarization tomography. This method utilizes three-dimensional (3D) inverse Radon transform to reconstruct the polarization quasiprobability distribution function of a state from the probability distributions measured for various Stokes observables. The reconstructed 3D distributions obtained for the macroscopic Bell states are compared with those obtained for a coherent state with the same mean photon number. The results demonstrate squeezing in one or more Stokes observables.

Determination of the Beam Coherence-Polarization Matrix of a Random Electromagnetic Beam

The beam coherence-polarization (BCP) matrix contains its elements in the form of mutual coherence functions. These are complex quantities governing the space-time correlations between the x and the y components of electric field at pair of points in the cross-section of the random electromagnetic beam. In this paper, we present mathematical expressions to determine the amplitude and the phase of the four elements of the BCP matrix which are a function of two spatial points in the optical field. We also determine experimentally the BCP matrix for an expanded laser beam introducing polarizers and rotators in widely separated beam paths of a modified version of the Youngs interferometer. The real and imaginary parts of the BCP matrix elements might show the change in the polarization properties of a random electromagnetic beam during its propagation. These results might be useful for astronomical measurements also.

Multiphoton nonclassical correlations in entangled squeezed vacuum states

Photon-number correlation measurements are performed on bright squeezed vacuum states using a standard Bell-test setup, and quantum correlations are observed for conjugate polarization-frequency modes. We further test the entanglement witnesses for these states and demonstrate the violation of the separability criteria, which infers that all the macroscopic Bell states, containing typically

Experimental observation of invariance of spectral degree of coherence with change in bandwidth of light

10^6

Experimental study of the relation between the degrees of coherence in space-time and space-frequency domain

photons per pulse, are polarization entangled. The study also reveals the symmetry of macroscopic Bell states with respect to local polarization transformations.

Polarization tomography of bright states of light

An experimental study is conducted to show the effect of the change in bandwidth of light on the spectral degree of coherence at a pair of points in the cross section of a beam. For this purpose a polychromatic source and a monochromator with variable entrance and exit slits were used to produce a variable bandwidth source. The classic Youngs interferometer was used to produce an interference pattern. The spectral measurements of the visibility of the interference fringes show that the spectral degree of coherence remains unaffected by the change in the frequency passband of the light.

Optical Cavity in Pulse Regime for Hybrid Variable Quantum Optics Applications

We present an experimental study showing the effect of the change in the bandwidth of light on the magnitude of both the complex degree of coherence and the spectral degree of coherence at a pair of points in the cross-section of a beam. A variable bandwidth source with a Youngs interferometer is utilized to produce the interference fringes. We also report for the first time that if the field is quasi-monochromatic or sufficiently narrowband, the elements of both the beam coherence polarization matrix and the cross-spectral density matrix, normalized to intensities (spectral densities) at the two points possess identical values.