Encoding technique for design of zero-order (on-axis) Fraunhofer computer-generated holograms

Area of Science:

• Optics and Photonics
• Diffractive Optics
• Nanophotonics

Background:

• Diffractive optical elements (DOEs) are crucial for manipulating light.
• Generating both phase and amplitude distributions, especially on-axis, presents challenges.
• Surface relief structures offer a phase-only approach to DOE design.

Purpose of the Study:

• To describe novel diffractive optical elements capable of generating on-axis distributions with both phase and amplitude control.
• To present a method for designing these elements using computer-generated masks and etching processes.
• To address and mitigate imperfections arising from the encoding method.

Main Methods:

• Design of surface relief plates as phase-only elements.
• Utilizing computer-generated masks with fixed spatial partitioning.
• Allocation of phase-only values to subelements for encoding.
• Implementation of common etching processes for fabrication.
• Development of error reduction techniques for noise mitigation.

Main Results:

• Successful generation of on-axis distributions with controlled phase and amplitude.
• Demonstration of surface relief plates as effective phase-only DOEs.
• Identification of noise sources inherent in the encoding process.
• Validation of error reduction methods for improved reconstruction fidelity.

Conclusions:

• The proposed phase-only diffractive optical elements offer a viable route for generating complex on-axis light distributions.
• Computer-generated masks combined with etching provide a practical fabrication approach.
• Error reduction strategies are essential for achieving high-quality reconstructed amplitude and phase patterns.