Abstract
Optical polyimide (PI) membrane is a promising substrate material for diffractive lens applied in future large-aperture space based imaging system because of its light weight, environmental adaptability and deployable feature. In this letter, we put forward a facile large-area uniform photolithography technique using vacuum assisted self contact method to fabricate large-aperture membrane diffractive lens. We fabricated a φ 400 mm aperture membrane off-axis 2-levels Fresnel Zone Lens (FZL) based on the method and achieved uniformly distributed photoresist morphology as well as over 36.6% average diffraction efficiency in full aperture. The results demonstrated that vacuum assisted self contact method effectively eliminates considerable air gaps caused by unevenness of large area photomask and substrate, thus facilitates uniform light field distribution in photoresist. This work provides reference to fabrication techniques of large aperture membrane diffractive lens, and offers feasible methods for future large area flexible electronics manufacturing.
Highlights
Optical polyimide (PI) membrane is a promising substrate material for diffractive lens applied in future large-aperture space based imaging system because of its light weight, environmental adaptability and deployable feature
We put forward a vacuum assisted self contact photolithography method and fabricated a φ 400 mm aperture PI membrane off-axis Fresnel Zone Lens (FZL) as a segmented primary lens based on this method and achieved good uniformity over full aperture
Sub-nanometer air gap distance can be achieved by decreasing vacuum pressure below 0.05 Pa super high resolution is possible for photolithography
Summary
Optical polyimide (PI) membrane is a promising substrate material for diffractive lens applied in future large-aperture space based imaging system because of its light weight, environmental adaptability and deployable feature. We put forward a facile large-area uniform photolithography technique using vacuum assisted self contact method to fabricate large-aperture membrane diffractive lens. The results demonstrated that vacuum assisted self contact method effectively eliminates considerable air gaps caused by unevenness of large area photomask and substrate, facilitates uniform light field distribution in photoresist. We put forward a vacuum assisted self contact photolithography method and fabricated a φ 400 mm aperture PI membrane off-axis FZL as a segmented primary lens based on this method and achieved good uniformity over full aperture. We discussed underlying mechanism through theoretical analysis and computer simulation, and demonstrated feasibility of this method in fabricating large area uniform membrane diffractive lens
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