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Proceedings Paper

Fabrication and replication of high efficiency blazed gratings with grayscale electron beam lithography and UV nanoimprint lithography
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Paper Abstract

In a waveguide-type display for augmented reality, the image is injected in the waveguide and extracted in front of the eye appearing superimposed on the real world scene. An elegant and compact way of coupling these images in and out is by using blazed gratings, which can achieve high diffraction efficiencies, thereby reducing stray light and decreasing the required power levels. This study investigates the fabrication of blazed gratings with grayscale electron beam lithography and the subsequent replication of the realized 3D grating structures in a polymer material with ultraviolet nanoimprint lithography. As such, diffractive elements are realized on a waveguide sheet, with very good control over the dimensions and the profile of the printed features. Blazed gratings are designed for green light (λ= 543 nm) and a diffraction angle of 43°. Making use of a PMMA resist and by carefully optimizing the electron-beam parameters, electron dose distributions and development step, blazed gratings with a pitch of 508 nm and a fill factor of 0.66 are achieved. Finally, a master is realized with two blazed gratings, 3 cm apart, which are replicated using ultraviolet nanoimprint lithography onto a waveguide sheet. The in- and outcoupling of an image through these two blazed gratings is shown, appearing sharp and non-distorted in the environment, and a throughput efficiency of 17.4% is confirmed.

Paper Details

Date Published: 28 February 2020
PDF: 11 pages
Proc. SPIE 11292, Advanced Fabrication Technologies for Micro/Nano Optics and Photonics XIII, 1129204 (28 February 2020); doi: 10.1117/12.2542171
Show Author Affiliations
Marie-Aline Mattelin, Ghent Univ. (Belgium)
imec (Belgium)
Ana Radosavljevic, Ghent Univ. (Belgium)
imec (Belgium)
Jeroen Missinne, Ghent Univ. (Belgium)
imec (Belgium)
Dieter Cuypers, Ghent Univ. (Belgium)
imec (Belgium)
Sander Kommeren, Morphotonics B.V. (Netherlands)
Jos Vandael, Zweko Optics BVBA (Belgium)
Jan Matthijs ter Meulen, Morphotonics B.V. (Netherlands)
Luc Verduyckt, Zweko Optics BVBA (Belgium)
Geert Van Steenberge, Ghent Univ. (Belgium)
imec (Belgium)

Published in SPIE Proceedings Vol. 11292:
Advanced Fabrication Technologies for Micro/Nano Optics and Photonics XIII
Georg von Freymann; Eva Blasco; Debashis Chanda, Editor(s)

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