arXiv subjects

Rajneesh Joshi

Publications and source records attributed to Rajneesh Joshi.

6 recordsLinked to original sources

arXiv2026

Modulation in degree of cross-polarization at Young's interferometer illuminated by non-uniformly polarized electromagnetic fields

The degree of cross-polarization (DoCP) and the electromagnetic degree of coherence (EM DoC) of an electromagnetic beam are investigated at the observation points for incoherent and non-uniformly polarized, i.e., different degree of polarization with respect to space at the two pinholes in Young's interference experiment. We note that DoCP at the observation plane can be expressed as the average value of the degree of polarization at the pinholes of Young's interference experiment. The present study also verifies that the DoCP is a two-point generalization of the DoP. Additionally, EM DoC at observation points can be controlled by DoP at pinholes. The findings may be useful for classical ghost imaging, lensless imaging, and the study of Stokes correlations.

physics.optics↗

arXiv2026

Electro-optically controlled photon group velocity, temporal walk-off and two-photon entanglement via nematic liquid crystal

The propagation of the quantum states of light in dispersive and anisotropic media is a fundamental problem in quantum optics. We present a unified theoretical framework for the propagation of the quantum states of light in voltage-controlled nematic liquid crystals, incorporating both material dispersion and electrically tunable birefringence. By treating photons as finite-bandwidth wave packets, we derive analytical expressions for group velocoity, temporal walk-off, and phase evolution of orthogonally polarized modes. The results demonstrate that nematic liquid crystals can serve as electrically tunable quantum photonic devices capable of manipulating photon arrival times, polarization correlations, and temporal indistinguishability of entangled photon pairs. These results show the direct relevance to quantum communication and photonic quantum information processing.

physics.optics↗

arXiv2026

Real-time polarization tuning in Mach-Zehnder interferometer using electro-optically modulated twist angles of nematic liquid crystal Note: This paper has been accepted for publication in "Journal of Theoretical and Applied Physics"

We propose a theoretical framework to dynamically control the degree of polarization of light by using the superposition of incoherent orthogonally polarized beams in a Mach-Zehnder interferometer incorporating a twisted nematic liquid crystal cell in one of its arms. The liquid crystal acts as an elecro-optically controlled polarization rotator, where the applied electric field changes the twist of molecules inside the nematic liquid crystal, thereby altering the plane of polarization. This controllable voltage dependent polarization rotation causes manipulation of the output degree of polarization. The resulting system allows real-time, tunable control over the degree of polarization, offering advantages over traditional static or reflection-based approaches, which often suffer from intensity losses or manual errors. We also observe that in the interference of fully coherent orthogonally polarized beams through a similar configuration, the degree of polarization is always equal to 1, whereas the orientation of linear state of polarization is changed with voltage.

physics.optics↗

arXiv2025

Cross-spectral purity: a generalization of spatiotemporal separability

We study the connection between cross-spectral purity and spatiotemporal separability of nonstationary (pulsed) scalar fields. It is found that in the case of complete coherence, there is a two-way relation between global cross-spectral purity and spatiotemporal separability of the field. Moreover, we show that cross-spectral purity generalizes the notion of spatiotemporal separability to partially coherent fields, due to the separability of the correlation functions. We also briefly discuss simple self-referencing linear measurement methods that can reveal cross-spectral purity.

physics.optics↗

arXiv2023

Cross-spectral purity of nonstationary vector optical fields: A similarity with stationary fields

This study establishes a reduction formula for nonstationary cross-spectrally pure vector light fields with any spectral bandwidth. The formation of a reduction formula, analogous to that for stationary fields, does not apply to the normalized two-time Stokes parameters of a nonstationary field that is cross-spectrally pure. The current formula incorporates time-integrated coherence parameters to ensure cross-spectral purity. The reduction formula derived for nonstationary vector light fields with arbitrary spectral bandwidth shares a similar mathematical structure to that of reduction formulas used for stationary vector fields. Additionally, we examine the requirement of strict cross-spectral purity for using a time-integrated coherence function, which exhibits a mathematical expression similar to that of strict cross-spectral purity in stationary vector fields. This investigation sheds light on the cross-spectral purity of pulse-type fields, which holds potential applications in the field of statistical optics.

physics.optics↗

arXiv2020

Degree of polarization of a spectral electromagnetic Gaussian Schell-model beam passing through 2-f and 4-f lens systems

Spectral electromagnetic Gaussian Schell-model (SEGSM) beam is a generalization of Gaussian Schell model beam having parameters with spectral dependence, which offers a basic classical model for random electromagnetic wide-sense statistically stationary beam-like fields. We study degree of polarization (DOP) of a SEGSM beam passing through 2-f and 4-f lens systems. It is observed that for a 2-f lens system, the spectral DOP at the back focal plane of the lens changes with respect to the transverse position from the optic axis, and the spectral parameters of the beam. For a 4-f lens system, the spectral DOP at the back focal plane is independent of the transverse position of the beam, whereas it depends on the beam parameters such as mean value of rms beam-width, rms width of correlation function, and size of aperture placed at the Fourier plane of the lens system.

physics.optics↗