Polarization State Of Light Beam Research Articles

Determination of Mueller Matrix for Metal Substrates by Stokes Polarimetry

This article focuses on a polarization measurement method based on Mueller calculus for determining the polarization properties of metal substrates. As the Mueller matrix of a medium provides all its polarization-altering properties, the presented method enables to predict the effect of any optically absorbing media on the polarization state of light beam. For the measurement, a polarized beam of light is reflected off the substrate under study and the change in state of polarization is measured in terms of Stokes parameters. Simple formulae have been derived to deduce the values of matrix elements from the measured Stokes parameters. The presented method facilitates determination of the optical properties of any absorbing medium even though the optical constants are unidentified. It has been validated by the estimation of Mueller matrix elements of a few metal reflectors (Cu, Al and SS304) using Fresnel’s equations and comparing the theoretical values with the experimentally determined values. It has been verified further by measuring the complex refractive index of a sample (brass: Cu–Zn alloy) using the principle angle method and comparing the results with that obtained by newly developed method. For the materials under study, the average absolute error in the measurement of matrix elements is found to be <0.01 and the standard deviation is <0.02. The main advantage of the method is that the polarization properties of any optically absorbing medium can be determined using a simple optical setup at any desired wavelength.

Condition for Gaussian Schell-model beam to maintain the state of polarization on the propagation in free space

In the free space optical communication system with circle polarization shift keying (CPolSK) modulation, the changes of polarization state of light beam have significant influence on the system performance. Keeping the state of polarization (SOP) unchanged on propagation can reduce the bit error rate. Based on the unified theory of coherence and polarization, we derive the sufficient condition for Gaussian Schell-model (GSM) beam to keep the SOP unchanged. We found that when the three spectral correlation widths (delta(xx), delta(yy) and delta(xy)) equal to each other and sigma(x) = sigma(y), the GSM beam maintains the SOP on propagation. This conclusion can be helpful for the design of the transmitter in the CPolSK system.

Polarization-encoded optical logic operations in photorefractive media

We propose and demonstrate optical logic operations using polarization encoding and wave mixing in photorefractive crystals. In our approach two orthogonal polarization states of light beams are used to represent respective logic values of 1 and 0. All 16 two-input logic operations can be easily achieved by use of the recording and readout of photoinduced volume gratings in photorefractive crystals. An optical full adder is also proposed and demonstrated.