For light fields, the coherence in longitudinal direction is governed by both the frequency spectra and angular spectra they possess. In this work, we develop and report a theoretical formulation to demonstrate the effect of the angular spectra of electromagnetic light fields in quantifying their longitudinal spatial coherence. The experimental results obtained by measuring the electromagnetic longitudinal spatial coherence and degree of cross-polarization of uniformly polarized light fields for different angular spectra validate the theoretical findings.

No abstract

We establish a generalized interference law characterizing longitudinal electromagnetic spatio-temporal coherence to determine the intensity and polarization modulations of light fields in the longitudinal direction. It is observed that under specific conditions, other interference laws can be deduced from the generalized interference law. Furthermore, the impact of different polarization and amplitude attributes of the source plane on the intensity and polarization modulations in the field has been quantified using two examples. In the case of orthogonal polarization features at the source points, we investigate the dependence of the degree of polarization (DOP) at the observation plane on the longitudinal shift and the angular spectra of the source for the time difference less than the coherence time. The weightage of the constituent orthogonal components plays a decisive role in governing DOP modulations. We obtain a constant DOP at the field point for identical polarization properties at the source points, independent of the coherence time. We have experimentally determined the DOP for both the polarizations, validating our theoretical findings.

We experimentally investigated the effect of polarization on Stokes scintillation for a generalized electromagnetic Gaussian-Schell model beam. The study remarkably provides a way to control the Stokes scintillations by varying the polarization properties of the source.

In this article, we report the experimental determination of Stokes fluctuations and Stokes scintillations for a generalized electromagnetic Gaussian-Schell model (EMGSM) beam. We have used an experimental scheme comprising three different interferometers which are aimed to tailor the correlation between orthogonal field components, synthesis of the generalized EMGSM beam, and observation of the spatial features of the light beam in the far zone. Stokes fluctuations matrix elements are measured for a partially polarized and unpolarized light beam. The weight value of the matrix elements is found to be dependent on the correlation strength parameter (|B_{xy}|) of the source. Experimental results for Stokes scintillations are also determined which depend drastically on the modulus value of B_{xy}. For asymmetrical coherence widths, variation in the Stokes scintillations is discerned across the beam diameter. The obtained results show a reasonable match with the theoretically expected values. The study reveals the source properties which can find applications in the areas of optical imaging, optical communication, etc.