arXiv subjects

C. S. Narayanamurthy

Publications and source records attributed to C. S. Narayanamurthy.

8 recordsLinked to original sources

arXiv2026

Geometric Manifold Statistics of Turbulence-Impacted Beam Propagation and Compensation in Optical Communication

The present study extends the analysis of turbulence-affected beam statistics through a manifold-based statistical framework that unifies probabilistic modeling with geometric interpretation. The spatial intensity distributions, distorted by dynamic turbulence, are represented using Gaussian Mixture Models (GMMs), whose probability landscapes are refined via Kernel Density Estimation (KDE) applied to pixel-level intensity data across temporal frames. The temporal evolution of turbulence is quantified by monitoring the variation of the unnormalized volumetric integrals under the GMM surfaces, providing a continuous measure of power redistribution within the optical field. Experimental investigations were carried out under four propagation conditions: turbulence-free reference, turbulence only, turbulence with a single PMMA compensator, and turbulence with dual PMMA compensators. To assess statistical dissimilarity, Affine-Invariant Riemannian Metric (AIRM) distances were computed between the covariance representations of successive frames, capturing the geometric evolution of beam topology in the space of Symmetric Positive Definite (SPD) matrices. Complementary topological distance analyses, performed with respect to the initial frame of each set, revealed distinct signatures of turbulence-induced aberrations and their progressive mitigation through dielectric compensation. The observed reduction in inter-frame distance metrics confirms the ability of coupled dipole interactions within PMMA slabs to partially restore statistical coherence in turbulence-distorted optical beams.

physics.optics↗

arXiv2026

Classical field statistical phase-space analysis of passive turbulence mitigation using PMMA dielectric media

This study examines the influence of optical turbulence on field statistics using a nonlinear reconstruction and quantum phase-space formalism. Turbulence-distorted intensity sequences were processed through a nonlinear P3-type partial differential equation to retrieve the embedded phase, thereby reconstructing the complete complex optical field. The recovered fields were subsequently projected onto a Gaussian local oscillator to generate quadrature ensembles, enabling Wigner function tomography via Radon inversion. Photon-number distributions were obtained from the overlap of the reconstructed Wigner functions with Fock-state kernels, allowing direct evaluation of statistical moments and the Fano factor. Comparative analysis across four experimental configurations, Set 1: uncorrected turbulence, Set 2: turbulence with a single PMMA slab, Set 3: turbulence with dual PMMA slabs, and Set 4: free-space reference revealed the modification of phase noise and photon statistics due to partial compensation. Notably, the evolution of the Fano factor traced the transition among Poissonian, super-Poissonian, and near-sub-Poissonian regimes, quantitatively capturing the degree of turbulence mitigation achieved by the PMMA elements. This framework establishes a quantitative link between turbulence-induced phase distortions and quantum statistical behavior of reconstructed optical fields.

physics.optics↗

arXiv2026

Spatio-Temporal Scintillation Mitigation via Polarizations Coupled Higher-Order Correlation

We present a unified theoretical framework linking second and fourth order statistical correlations of stochastic electromagnetic beams to the scintillation index observed after propagation through Kolmogorov atmospheric turbulence. We derive the beam coherence polarization matrix and its propagation law in a random medium. An algebraic connection is established between the second order polarization matrix J, its fourth order Gram counterpart obtained from the square of J, the classical degree of polarization P, the fourth order degree of polarization, and the scintillation index of the beam intensity. A key result is a closed form purity relation connecting the trace of the squared polarization matrix to the square of its trace, which shows that unpolarized natural beams exhibit a large scintillation index. The analysis demonstrates that scintillation can be reduced by polarizing the beam using suitable polarizer sets. This reduction occurs independently of the atmospheric turbulence strength parameter. Experimental results further show that simultaneous control of coherence and polarization, achievable using a pseudo random phase plate, provides a practical approach for minimizing scintillation in free space optical communication links.

physics.optics↗

arXiv2026

Spatiotemporal Stabilization of Turbulence-Distorted Gaussian Beams via Waveguide Spatial Filtering

Optical beams propagating through atmospheric turbulence undergo spatiotemporal intensity fluctuations that deviate significantly from an ideal Gaussian profile. In this work, we present a unified theoretical and experimental framework for quantifying and mitigating these turbulence-induced distortions by coupling a higher-order statistical characterization technique with optical waveguide spatial filtering. The statistical characterization employs a Cholesky-whitened Gram--Charlier expansion that decomposes the two-dimensional beam intensity distribution into a Gaussian core augmented by third- and fourth-order cumulant corrections, thereby isolating skewness and excess kurtosis as quantitative non-Gaussianity indicators. Concurrently, the propagation of the distorted beam through a dielectric waveguide is analyzed to demonstrate that higher-order spatial modes, which carry the dominant share of turbulence-induced structural distortions, encounter a cutoff condition governed by the normalized frequency parameter and subsequently undergo exponential attenuation along the propagation direction. The waveguide thus acts as a passive spatial mode filter that selectively transmits the fundamental guided mode while suppressing radiative higher-order modes. The fitted beam volume, derived from the Gram--Charlier intensity model, serves as a unified scalar diagnostic that tracks the frame-by-frame evolution of turbulence-induced structural changes. Experimental measurements validate the theoretical predictions, demonstrating a substantial reduction in intensity fluctuations and a recovery of Gaussian beam statistics after waveguide propagation.

physics.optics↗

arXiv2025

Conventional Scintillation Statistics with Turbulence Impacted Coupled Dipole Oscillation

We investigate the propagation of optical fields through polymethyl methacrylate (PMMA) rods under atmospheric turbulence conditions, employing a generalized Lorentz dipole oscillator model with nonlinear restoring forces and dipole-dipole coupling. The theoretical framework incorporates second- and third-order anharmonic terms ($β_i|r_i|r_i$ and $α_i|r_i|^2r_i$) alongside dyadic Green's function-mediated coupling between localized dipoles. Gradient forces arising from spatially non-uniform field distributions and Lorentz force perturbations are incorporated through d'Alembert's principle, revealing an effective inertia mechanism that opposes rapid field redistribution. Modal diagonalization demonstrates that synchronized dipole oscillations can compensate turbulence-induced wavefront distortions, with the perturbation force $δF_{\text{Pert}}(t) = F'_{\text{Inertia}} - F_{\text{Inertia}}$ governing the compensation efficacy. Experimental verification employs a pseudo-random phase plate (PRPP) generating Kolmogorov-spectrum turbulence, with 200 frames recorded across four configurations: baseline, turbulence-only, and turbulence with one or two PMMA rods. Statistical analysis quantifies scintillation index variations. Results indicate that dipole-dipole coupling energy transitions enable partial turbulence compensation when stronger suppression observed for longer propagation paths through increased synchronization.

physics.optics↗

arXiv2025

Turbulence Impacted Wavefront Corrections Using Beam Modulation Technique

New experimental technique have been proposed to discuss the turbulence impact reduction using beam shaping technique. In first phase of experiments, turbulence Impacted Vortex beam shaping technique has been introduced for a propagating beam which is effected by Kolmogorov type lab based turbulence simulator using Pseudo Random Phase Plate (PRPP). The new technique is executed with a spatially filtered collimated Gaussian beam that is propagated through computer controlled rotating PRPP to introduce the lab based turbulence on the beam profile. The turbulence impacted beam is then propagated through Vortex Phase Plate (VPP) to shape that beam into different topological charged Laguerre Gaussian modes and further collimated using two lens based configuration. We have measured the scintillation index of the spatial intensity profile collected from CCD. Comparative studies have been done by placing the image plane in five different positions on the propagation path of the beam so that we can detect Collimated, diverging and converging outputs. Four topological charges of LG beams and Gaussian beam have been used to envisage results.

physics.optics↗

arXiv2025

Turbulence Impacted Beam Statistics and Image Topology with Lorentz Dipole Oscillation

This work presents a rigorous statistical and geometric framework for analyzing turbulence-impacted beam propagation and image topology with results obtained using a PMMA slab. The approach models beam intensity distributions as n-dimensional data set represented through Gaussian Mixture Models (GMMs), embedding them into the manifold of Symmetric Positive Definite (SPD) matrices. By employing information geometric tools, geodesic distances, and affine-invariant Riemannian metrics, we establish a principled methodology for quantifying similarity and dissimilarity among beam images. Experimental results demonstrate topological distance trends, distance statistics, and correlation measures for different turbulence scenarios, including polarized and unpolarized cases. Histograms of distance statistics reveal stable statistical features, with correlation coefficients highlighting the turbulence-induced variability in PMMA-based beam propagation. The framework not only provides a systematic foundation for analyzing optical beam statistics under turbulence but also opens avenues for advanced applications such as deep learning-based feature reduction, image compression, and secure free-space optical (FSO) communication. Future directions include refining the GMM-EM based distance measures, comparative scatter analysis, and developing robust statistical tools for turbulence imaging. Overall, this study bridges theoretical modeling, experimental validation, and potential technological applications in adaptive and applied optics.

physics.optics↗

arXiv2025

Coupled Dipole Oscillation Enabled Scintillation Compensation in Turbulence-Impacted Laser Beam

The present work develops a rigorous framework for collective dipole oscillations in dense dielectric media by extending the Lorentz oscillator model to include both quadratic (second order) and cubic (third order) nonlinear restoring forces. Dipole-dipole interactions are incorporated via the dyadic Greens function, leading to a nonlocal description of the medium. Starting from the generalised oscillator equation, the system is expressed in matrix form with an effective stiffness matrix. Using a harmonic steady state ansatz, nonlinear terms are approximated in the frequency domain. Diagonalisation provides collective normal modes, which serve as a basis for perturbative expansion zeroth order captures the linear response, while higher orders describe nonlinear corrections. The polarisation is expressed through corrected mode amplitudes, yielding an effective nonlinear nonlocal susceptibility kernel. Finally, the scalar Greens function formalism is applied to derive the structured output field. These approaches bridge microscopic dipole dynamics with macroscopic optical propagation, offering key insights into nonlinear light matter interaction and turbulence influenced field evolution.

physics.optics↗