研究目的
To investigate the evolution of optical fields carrying orbital angular momentum under arbitrary scintillation conditions in atmospheric turbulence, comparing predictions from the infinitesimal propagation equation and single-phase screen methods with numerical simulations.
研究成果
The IPE predictions are more reliable than SPS predictions under strong scintillation conditions, as validated by numerical simulations. The deviation between IPE and SPS occurs at a scale that depends on turbulence strength, indicating the breakdown of the SPS approximation. This has implications for free-space optical communication systems using orbital angular momentum modes.
研究不足
The IPE relies on the quadratic structure function approximation, which may deviate from exact Kolmogorov statistics under strong scintillation. Numerical simulations are limited by computational resources and the accuracy of phase screen generation, including the exclusion of very low spatial frequencies without subharmonics correction.
1：Experimental Design and Method Selection:
The study uses theoretical models (SPS and IPE methods) and numerical simulations based on the Kolmogorov theory of turbulence. The IPE is an analytical approach for modeling propagation, while SPS is an approximation. Numerical simulations employ a split-step method with multiple phase screens to simulate wave propagation.
2：Sample Selection and Data Sources:
Input optical field is a Laguerre-Gauss mode with azimuthal index l=1 and radial index p=0. Turbulence conditions are varied using normalized turbulence strength K and propagation distance t.
3：Turbulence conditions are varied using normalized turbulence strength K and propagation distance t.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: No specific physical equipment is mentioned; the work is computational, involving numerical simulations and theoretical calculations.
4：Experimental Procedures and Operational Workflow:
For numerical simulations, the split-step method is used: modulate the optical field with random-phase screens (generated using Kolmogorov power spectral density and subharmonics method) and propagate through free space in steps. Multiple realizations (e.g., 1000 runs) are performed to compute average power fractions and standard errors.
5：Data Analysis Methods:
Power fractions in LG modes are computed from overlaps between input and output modes. Statistical analysis includes calculating averages and standard errors from simulation results. Theoretical predictions are derived from IPE and SPS equations.
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