Geometry-aware phase compensation for sampling-efficient angular spectrum method

Area of Science:

• Optics and Photonics
• Computational Electromagnetics
• Optical Engineering

Background:

• Conventional angular spectrum method (ASM) has limitations in modeling thick optical systems due to dense grid requirements.
• Scalability issues arise in ASM for wide-angle and large-aperture optical configurations.
• Accurate modeling of thick refractive and diffractive elements is crucial for advanced optical design.

Purpose of the Study:

• To introduce an efficient wave optical modeling framework for thick refractive and diffractive systems.
• To overcome the computational bottlenecks of conventional ASM.
• To enable gradient-based inverse design for complex optical systems.

Main Methods:

• Developed a geometry-aware, phase-compensated angular spectrum method (GAPC-ASM).
• Unified carrier frequency shifting and global phase compensation.
• Introduced a local phase compensation mechanism for geometry-dependent path length variations.

Main Results:

• GAPC-ASM enables single-slice modeling of thickness-induced geometrical distortion.
• Significantly reduced axial sampling requirements in multi-slice ASM.
• Demonstrated efficiency, differentiability, and suitability for inverse design.

Conclusions:

• The proposed GAPC-ASM framework is a reliable and physically consistent tool for wave optical design.
• Validated through inverse design of lenses and fabrication of a freeform phase mask.
• The fabricated mask improved lensless imaging reconstruction quality, matching simulations.