Wide-window angular spectrum method for diffraction propagation in far and near field.

Area of Science:

• Optics and Photonics
• Computational Physics

Background:

• Traditional angular spectrum (AS) and band-limited AS (BLAS) methods face limitations in simulating free-space diffraction propagation, particularly over long distances.
• Sampling issues in the transfer function and decreasing accuracy with propagation distance hinder the effectiveness of AS and BLAS methods.
• While wider calculation windows reduce numerical errors, they significantly increase computational burden.

Purpose of the Study:

• To propose a novel, highly accurate, and computationally efficient method for simulating free-space diffraction propagation.
• To address the limitations of existing AS and BLAS methods concerning accuracy and computational cost for varying propagation distances.

Main Methods:

• Developed a novel simulation technique that improves upon AS and BLAS methods.
• Optimized calculation window size based on the Nyquist theorem to ensure effective sampling in the frequency domain.
• Utilized linear convolution, evaluated via fast Fourier transform, to achieve computational complexity independent of window size.

Main Results:

• The proposed method demonstrates high accuracy for both near-field and far-field propagation simulations.
• Achieved computational efficiency where complexity is not dependent on the calculation window size.
• Overcame the sampling limitations and accuracy degradation issues inherent in AS and BLAS methods for long-distance propagation.

Conclusions:

• The novel method provides a significant advancement in simulating free-space diffraction propagation.
• Offers a robust solution for accurate and computationally feasible optical simulations across diverse propagation scenarios.
• Presents a valuable tool for researchers and engineers in optics and photonics.