Study of structured light propagation in atmospheric turbulence and dielectric media

Abstract

This thesis is inspired by the substantial advancements in structured light and ultrafast phenomena. The thesis numerically explores the propagation of structured light in atmospheric turbulence and dielectric media. We first investigate the dynamics of Abruptly autofocusing (AAF) beams in turbulent atmosphere of different strengths. Initially, we model the propagation of ring Pearcey vortex beam (RPVB) in turbulent atmosphere, and it is found that upon increasing the value of topological charge 𝑙, aperture averaged scintillation index (SI) increases in both moderate and strong turbulences. Integration of the negative spatial chirp in RPVB at the input, significant improvement in aperture averaged SI has been observed. On comparing the aperture averaged SI of RPVB with another AAF beam namely ring Airy vortex beam (RAVB), it is found that RPVB outperforms RAVB at larger propagation distances in strong atmospheric turbulence. Additionally, RPVB exhibits superior beam wander performance as compared to RAVB in both moderate and strong turbulences. Further, examination of the channel efficiency and orbital angular momentum (OAM) spectra of these AAF beams in weak and moderate atmospheric turbulences reveals that RAVB outperforms RPVB in these terms as well. Furthermore, the propagation of RAGV beam in harmonic parity time (PT)-symmetric potential has been studied and it is reported that by manipulating the beam's input parameters and the loss/gain coefficients of the potential one can control the beam evolution dynamics to a significant extent. The thesis systematically explores the behaviour of ultrashort optical vortices in both space-time separable and non-separable cases in dispersive and nonlinear media employing nonlinear envelope equation. In space-time separable pulse case, at bright caustic of the ultrashort Laguerre-Gauss vortex, pulse focuses in temporal domain in weaker nonlinearity. However, in stronger nonlinearity asymmetric temporal splitting is observed at the bright caustic. In spatial domain also at 𝑡=0 in pulse frame, focusing and splitting are observed that depends upon strength of nonlinearity. In spectral domain, self-phase modulation and self-steeping induced spectrum is observed at bright caustic. For space-time non-separable ultrashort LG vortex with power exponential spectrum, we find that upon moving radially outwards from the bright caustics or towards the phase singularity redshift and blueshift in spectrum is observed respectively. Additionally, it is reported that temporal and frequency chirp profiles of the pulse vary uniquely in different spatial regions in the transverse profile of the pulse. Furthermore, the effects of the incorporation of frequency chirp on the pulse dynamics are studied.