Analysis and optimization of fabrication of continuous-relief diffractive optical elements.

Area of Science:

• Optics and Photonics
• Materials Science and Engineering

Background:

• Direct laser beam writing is a key technique for fabricating diffractive optical elements (DOEs).
• Fabrication limitations, such as rounded profile steps, can reduce the optical performance of DOEs.

Purpose of the Study:

• To analyze the fabrication of continuous-relief DOEs using direct laser beam writing.
• To identify limitations and quantify their influence on optical performance.
• To present optimization techniques for improving diffraction efficiency.

Main Methods:

• Analysis of direct laser beam writing in photoresist for DOE fabrication.
• Quantification of the impact of fabrication tolerances on optical performance.
• Development and application of optimization techniques, including profile depth scaling and nonlinear exposure compensation.

Main Results:

• Rounded profile steps in fabricated structures were identified as a primary cause of reduced diffraction efficiency.
• Scaling the profile depth was shown to increase first-order diffraction efficiency for blazed elements.
• Nonlinear compensation for Gaussian beam convolution improved diffraction efficiency by 18% for a blazed grating, reaching 79%.

Conclusions:

• Direct laser beam writing of DOEs can be optimized to overcome fabrication limitations.
• Optimization techniques effectively enhance diffraction efficiency and suppress unwanted diffraction orders.
• The presented methods offer a pathway to improved performance in diffractive optical elements and computer-generated holograms.