Fabrication of Micro-Optics Elements with Arbitrary Surface Profiles Based on One-Step Maskless Grayscale Lithography

Area of Science:

• Microfabrication
• Optical Engineering
• Materials Science

Background:

• Maskless lithography offers advantages for micro-optics fabrication.
• Digital micro-mirror devices (DMDs) enable flexible exposure control.
• Nonlinear relationships in DMD grayscale levels and photoresist exposure depth complicate precise surface profiling.

Purpose of the Study:

• To develop a maskless lithography method for rapid, cost-effective fabrication of micro-optics with arbitrary surface profiles.
• To propose a compensation strategy for nonlinear effects in DMD-based lithography.
• To ensure accurate control of micro-optic surface topographies.

Main Methods:

• Utilized a digital micro-mirror device (DMD) to modulate exposure dose based on desired surface profiles.
• Developed a compensation method to address nonlinearities between DMD grayscale levels and exposure dose.
• Developed a compensation method to address nonlinearities between exposure dose and photoresist exposure depth.
• Fabricated and tested micro-optic elements with spherical, aspherical, and conic surfaces.

Main Results:

• Achieved precise control over arbitrary surface profiles in micro-optics fabrication.
• The proposed compensation method effectively mitigated fabrication errors.
• Demonstrated a root-mean-square (RMS) surface height error of approximately 0.1 μm.
• Successfully fabricated diverse micro-optic elements including spherical, aspherical, and conic surfaces.

Conclusions:

• The developed maskless lithography method with nonlinear effect compensation enables accurate fabrication of micro-optics.
• This approach offers a reliable and precise way to control arbitrary surface profiles.
• The technique is directly applicable to controlling DMD grayscale levels for complex micro-optic structures.