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Title: Broadband Polarization Gratings for Efficient Liquid Crystal Display, Beam Steering, Spectropolarimetry, and Fresnel Zone Plate.
Authors: Oh, Chulwoo
Advisors: Philip J. Bos, Committee Member
Jan Genzer, Committee Member
David E. Aspnes, Committee Member
David Schurig, Committee Member
Michael J. Escuti, Committee Chair
Keywords: Beam Steering
Liquid Crystal
Beam Shaping
Issue Date: 30-Nov-2009
Degree: PhD
Discipline: Electrical Engineering
Abstract: We introduce achromatic polarization gratings (PGs) as broadband polarizing beam splitters, which exhibit practically ~100% efficient diffraction over a wide range of spectrum. We have experimentally demonstrated high-quality achromatic PGs fabricated using holographic photoalignment techniques for liquid crystal (LC) materials. Non-ideal diffraction behaviors of the PGs have been investigated beyond the paraxial limitations (i.e., small grating periods, oblique incidence, and finite gratings) via extensive numerical analysis based on the finite-difference time-domain method. Design and fabrication of small-period PGs are also discussed to show how to achieve high diffraction efficiency and large diffraction angles at the same time. Three key innovative technologies utilizing the unique diffraction properties of the PGs have been introduced and experimentally demonstrated. The first application for light-efficient LC displays is the polymer-PG display. We have developed a prototype projector based on the polymer-PG display as a viable solution for ultra-bright pico-projector applications. Second, two novel beam steering concepts based on the PG diffraction have been proposed: a non-mechanical, wide-angle beam steering system using stacked PGs and LC waveplates and the Risley grating as a thin-plate version of the Risley prism. The third PG application is in advanced imaging and non-imaging spectropolarimetry. In the last part of this Dissertation, we introduce a polarization-type Fresnel zone plates (P-FZPs), comprising of spatial-variant linear birefringence or concentric PG (CPG) patterns. We have experimentally demonstrated high-quality P-FZPs, which exhibit ideal Fresnel-type lens effects, formed as both LC polymer films and electro-optical LC devices. In summary, we have explored the fundamental diffraction behavior of the polarization gratings and their applications in various optics and photonics technologies. We conclude this Dissertation with our suggestions of a number of potential innovations and advances in technologies that can be enabled by polarization gratings and related technologies.
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