全息术
材料科学
偏斜
极化(电化学)
光学
偏振器
衍射效率
液晶
光电子学
衍射
物理
栅栏
双折射
化学
物理化学
作者
Nathaniel Z. Warriner,Michael J. Escuti
摘要
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%.
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