Diffraction algorithm suitable for both near and far field with shifted destination window and oblique illumination

Area of Science:

• Optics and Photonics
• Computational Physics
• Wave Propagation

Background:

• Accurate simulation of optical diffraction is crucial for various applications.
• Existing methods face challenges with non-ideal conditions like shifted windows and oblique illumination.
• The angular spectrum theory provides a foundation for diffraction modeling.

Purpose of the Study:

• To develop a robust method for free-space diffraction simulation under conditions of a shifted destination window and large oblique illumination.
• To analyze and mitigate sampling errors in numerical diffraction simulations.
• To propose a unified algorithm for both near-field and far-field diffraction.

Main Methods:

• Derivation of a generalized transfer function (GTF) and generalized point-spread function (GSPF) based on angular spectrum theory.
• Analysis of sampling errors associated with Fast Fourier Transform (FFT) implementations of GTF and GSPF.
• Determination of a critical distance (Zc) to differentiate sampling method suitability.
• Development of a hybrid GTF-GSPF algorithm.

Main Results:

• The study identified distinct criteria for FFT-based GTF (distance ≤ Zc) and GSPF (distance ≥ Zc) sampling.
• An analytical formula for the criteria distance Zc was established.
• The proposed hybrid GTF-GSPF algorithm effectively handles both near- and far-field diffraction simulations.
• Simulation results validated the algorithm's feasibility and accuracy.

Conclusions:

• The hybrid GTF-GSPF algorithm provides a unified and accurate approach for diffraction simulation with shifted windows and oblique illumination.
• The method overcomes limitations of traditional GTF and GSPF sampling techniques.
• This work advances numerical diffraction modeling capabilities for complex optical scenarios.