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Proceedings Paper

High-efficiency Fresnel lens design and fabrication in a two-stage photopolymer
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Paper Abstract

Diffractive optical elements (DOEs) assimilate optical functionality within thin (≤100 μm), lightweight films. With the recent advent of high dynamic range two-stage photopolymers, gradient-index volume DOEs can now achieve diffraction efficiencies competitive with conventional surface-relief DOEs, while also offering the advantages of contact-free, selfprocessing optical recording into a flat film that can be laminated between protective sheets. Here we design and fabricate Fresnel lenses with what we believe to be the highest reported diffraction efficiencies achieved to date using this gradientindex DOE approach. Our analysis demonstrates that these high diffraction efficiencies are crucially enabled by the high index modulation of the photopolymer, Δn < 0.01. Another factor enabling high diffraction efficiency is the pixel count of the recording exposure. Thus, we use a photolithographic chrome mask with 9000 × 9000 pixels of 2.5 μm diameter, significantly exceeding the pixel count available from spatial light modulators. The mask is imaged onto photopolymer films of 50 μm thickness, and Fresnel patterns of up to 23 mm diameter are recorded in one-shot exposures. The resulting lenses range from f/44 – f/79 with diffraction efficiencies up to 83%. The performance of various lens designs is validated by an analysis showing that, for a given Δn, there is a fundamental trade-off between low f/# and high diffraction efficiency. This high performance represents an important step toward practical applications, ranging through solar energy concentrators, customized vision optics, integrated photonics, heads-up displays, and hybrid lenses.

Paper Details

Date Published: 23 April 2019
PDF: 9 pages
Proc. SPIE 11030, Holography: Advances and Modern Trends VI, 110300P (23 April 2019); doi: 10.1117/12.2521004
Show Author Affiliations
John E. Hergert, Univ. of Colorado Boulder (United States)
David J. Glugla, Univ. of Colorado Boulder (United States)
Amy C. Sullivan, Univ. of Colorado Boulder (United States)
Marvin D. Alim, Univ. of Colorado Boulder (United States)
Robert R. McLeod, Univ. of Colorado Boulder (United States)

Published in SPIE Proceedings Vol. 11030:
Holography: Advances and Modern Trends VI
Antonio Fimia; Miroslav Hrabovský; John T. Sheridan, Editor(s)

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