Iterative scalar nonparaxial algorithm for the design of Fourier phase elements

Area of Science:

• Optics and Photonics
• Diffractive Optics
• Computational Electromagnetics

Background:

• Designing diffractive optical elements (DOEs) with subwavelength features is challenging.
• Traditional scalar paraxial approximations limit the design of high-performance DOEs for large diffraction angles.
• Need for efficient algorithms to design DOEs with nanoscale features.

Purpose of the Study:

• To propose and validate a novel iterative algorithm for designing Fourier diffractive optical elements (DOEs).
• To enable the design of DOEs with feature sizes on the order of the illumination wavelength.
• To improve DOE performance compared to existing scalar paraxial methods.

Main Methods:

• Developed an iterative algorithm utilizing a scalar nonparaxial propagator.
• Employed iterative Fourier transform and iterative projection techniques.
• Validated simulation results with experimental data.

Main Results:

• The proposed algorithm yields higher-performance DOEs than purely scalar paraxial designs.
• Achieved comparable calculation times to existing methods.
• Experimental verification confirmed the method's validity for feature sizes down to half the wavelength and diffraction angles up to 37°.

Conclusions:

• The scalar nonparaxial propagator-based iterative algorithm is effective for designing advanced Fourier DOEs.
• The method successfully designs DOEs with subwavelength features and large diffraction angles.
• This approach offers a valid and efficient design strategy for next-generation optical elements.