MODELLING OF STRUCTURED BEAM PROPAGATION THROUGH ATMOSPHERIC & OCEANIC TURBULENCES

Abstract

In this study we numerically model the optical beam propagation through random media. The propagation characteristics of various structured optical beams are studied in both atmospheric and oceanic turbulences. Utilizing the multiple-phase screen approach, we simulate the behavior of various structured optical beams. We initially propagate the fundamental Gaussian beam in free space, observing the broadening of its width due to diffraction. Subsequently, we analyze the propagation of Laguerre-Gaussian (LG) beam with different orbital angular momentum states (OAM) under moderate to high atmospheric turbulence, noting significant distortions in the irradiance pattern. Additionally, we calculate the scintillation index (SI) for Gaussian beams in moderate to high oceanic turbulence, finding a maximum SI value of 2.5 under high atmospheric turbulence conditions. We present a comprehensive numerical study of the structured beams through oceanic turbulence. The degradation in the intensity of the Gaussian beam for different turbulent parameters is presented. The irradiance pattern for LG beam and ring Airy vortex beam (RAVB) shows that the RAVB is less affected by the oceanic turbulence due to non-diffracting, selffocusing, and self-healing properties. Our analysis reveals the impact of turbulence on beam characteristics such as beam width, irradiance pattern, and SI. A comparative study of SI for Gaussian beam and RAVB is shown where the RAVB has lesser SI for low and moderate oceanic turbulence. The mean signal-to-noise ratio (SNR) of the RAVB has been calculated for low to moderate oceanic turbulent conditions. The SNR substantially decreases with increase in the propagation distance. Compared to other beams, the RAVB shows phenomenal performance while propagating through oceanic turbulence. Meanwhile, no one has studied the propagation of the RAVB through oceanic turbulence to the best of our knowledge. Therefore, the RAVB has the potential advantage of mitigating the effect of turbulence, and hence, it can be used as the carrier wave in underwater communication.