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Turbulence Impacted Wavefront Corrections Using Beam Modulation Technique

Shouvik Sadhukhan, C. S. Narayanamurthy

TL;DR

The paper investigates mitigating turbulence-induced distortions on propagating beams by post-turbulence beam modulation. Using a lab-based Kolmogorov-type turbulence simulated with a rotating PRPP, a VPP converts Gaussian beams to Laguerre-Gaussian modes after turbulence, with five measurement planes analyzed via scintillation and beam wandering metrics. The main finding is that shaping turbulence-impacted beams into LG modes (charges 1–4) after the turbulence reduces scintillation compared to propagation through turbulence alone, though beam wandering shows charge-dependent behavior. This beam-modulation approach offers a potential alternative to adaptive optics for robust free-space optical communication under dynamic atmospheric conditions, validated by quantitative SI and centroid analyses across multiple planes.

Abstract

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.

Turbulence Impacted Wavefront Corrections Using Beam Modulation Technique

TL;DR

The paper investigates mitigating turbulence-induced distortions on propagating beams by post-turbulence beam modulation. Using a lab-based Kolmogorov-type turbulence simulated with a rotating PRPP, a VPP converts Gaussian beams to Laguerre-Gaussian modes after turbulence, with five measurement planes analyzed via scintillation and beam wandering metrics. The main finding is that shaping turbulence-impacted beams into LG modes (charges 1–4) after the turbulence reduces scintillation compared to propagation through turbulence alone, though beam wandering shows charge-dependent behavior. This beam-modulation approach offers a potential alternative to adaptive optics for robust free-space optical communication under dynamic atmospheric conditions, validated by quantitative SI and centroid analyses across multiple planes.

Abstract

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.
Paper Structure (14 sections, 23 equations, 23 figures)

This paper contains 14 sections, 23 equations, 23 figures.

Table of Contents

  1. Introduction
  2. Theoretical Procedures and Mathematical Methodology
  3. Laguerre Gaussian Beam and its Topological Charges
  4. Conversion from Symmetric Gaussian Wavefront to Vortex Gaussian Wavefront
  5. Pseudo Random Phase Plate: Mathematics of Beam Patches
  6. Polarized light Propagation through PRPP Turbulence
  7. Complex Wavefront Propagation through PRPP Turbulence
  8. Kolmogorov Statistics for Turbulence
  9. Scintillation Index and Relative Noise Mapping
  10. Experimental Procedures and Results
  11. Description of Experimental Setup
  12. Results and Discussion
  13. Beam Wandering effect on Turbulence impacted beam shaping
  14. Conclusion

Figures (23)

  • Figure 1: Pictorial representations Pseudo Random Phase Plate
  • Figure 2: Pictorial representations Vortex Phase Plate
  • Figure 3: Phase distribution imprinted onto the transverse plane of an incident beam
  • Figure 4: Experimental diagram of turbulence impacted beam shaping
  • Figure 5: SI Comparison for different Beams; Blue: LG beams propagated without Turbulence; Red: LG beams shaped after Turbulence; Green: LG beams propagated through Turbulence for Plane 1
  • ...and 18 more figures