Etch-free additive lithographic fabrication methods for reflective and transmissive micro-optics.

Area of Science:

• Optics and Photonics
• Microfabrication Technologies
• Materials Science

Background:

• Diffractive optical elements (DOEs) are crucial for micro-optics applications.
• Traditional photolithography and reactive-ion etching (RIE) methods for DOEs suffer from etching artifacts, limiting optical accuracy and surface quality.
• There is a need for versatile, high-quality fabrication methods for multi-level DOEs.

Purpose of the Study:

• To propose and demonstrate an alternative additive fabrication method for multi-level DOEs.
• To overcome the limitations of traditional etching techniques in DOE fabrication.
• To achieve high accuracy in depth, surface roughness, uniformity, and smoothness for DOEs.

Main Methods:

• Additive fabrication of multi-level microstructures by deposition and lift-off, avoiding reactive-ion etching (RIE).
• Precise control over deposition parameters to achieve desired feature depths and uniformity.
• Utilizing the fabricated structures as reflective DOEs or as master stamps for nanoimprinting refractive DOEs.

Main Results:

• Demonstrated a novel additive method for fabricating multi-level DOEs with high accuracy.
• Achieved excellent control over depth accuracy, surface roughness, uniformity, and smoothness.
• Successfully fabricated both reflective and transmissive DOEs for imaging and display applications.
• Uniform depths were realized for features at both micrometer and millimeter scales simultaneously.

Conclusions:

• The proposed additive fabrication method provides a versatile and high-quality alternative to traditional etching for DOE production.
• This technique enables precise control over microstructural features, enhancing DOE performance.
• The method is effective for creating DOEs suitable for diverse imaging and display applications.