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Proceedings Paper

Fabrication of liquid crystal binary polarization gratings (bin-PGs)
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Paper Abstract

Planar, anisotropic liquid crystal (LC) optics, along with metasurfaces, have shown to be the predominant meth- ods of producing a geometric (or Pancharatnam-Berry) phase hologram (GPH). One of the simplest GPHs, the traditional continuous polarization grating (PG), implements a continuous linear phase ramp. This PG has received significant attention due to its polarization-selective nature and 100% diffraction efficiency. However, when this linear phase is sampled with a 0-π alternating phase profile, theoretical reasoning predicts polarization- independent qualities. In order to distinguish this grating from continuous PGs, we call this a binary polarization grating (bin-PG). Traditional PGs, with a continuously varying nematic director profile, are simple to manufacture with many holographic methods. However, no bin-PG fabricated with patterned LCs have yet been reported. In this work, we experimentally study bin-PGs formed using a photo-aligned LC polymer network. Particular attention is brought to the problematic rotational ambiguity of LC at the phase step. To prevent disclination lines, a rotation biasing pixel of varying size is implemented at the phase transition boundary. We measure the diffraction efficiencies, the input polarization response, and the impact of the non-zero transition region. At the smallest transition pixel size (0.625μm) an average +1-order efficiency of 36% was measured with an input-polarization sensitivity of only ±1.7%.

Paper Details

Date Published: 29 August 2019
PDF: 6 pages
Proc. SPIE 11092, Liquid Crystals XXIII, 110920Q (29 August 2019); doi: 10.1117/12.2530131
Show Author Affiliations
N. Zane Warriner, North Carolina State Univ. (United States)
Michael J. Escuti, North Carolina State Univ. (United States)

Published in SPIE Proceedings Vol. 11092:
Liquid Crystals XXIII
Iam Choon Khoo, Editor(s)

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