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Xiang, Xiao.

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Model-Based Design and Fabrication of Subwavelength and Nonlinear Geometric Phase Holograms.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Model-Based Design and Fabrication of Subwavelength and Nonlinear Geometric Phase Holograms./
Author:	Xiang, Xiao.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2018,
Description:	139 p.
Notes:	Source: Dissertation Abstracts International, Volume: 79-06(E), Section: A.
Contained By:	Dissertation Abstracts International79-06A(E).
Subject:	Optics. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=11017887

Model-Based Design and Fabrication of Subwavelength and Nonlinear Geometric Phase Holograms.
Xiang, Xiao.

Model-Based Design and Fabrication of Subwavelength and Nonlinear Geometric Phase Holograms. - Ann Arbor : ProQuest Dissertations & Theses, 2018 - 139 p.

Source: Dissertation Abstracts International, Volume: 79-06(E), Section: A.

Thesis (Ph.D.)--North Carolina State University, 2018.

Efficiently deflecting light into large angles is important for various applications including beam steering, spectroscopy, optical communication and the emerging wearable displays for virtual/augmented reality (VR/AR) systems. Another important demand for many optical systems is arbitrary and accurate wavefront shaping by a monolithic and low-cost element. Compared to refractive elements, diffractive optical elements (DOEs) provide compact and lightweight solutions. One of the challenges is achieving wide angular acceptance, high efficiency and large deflection angle. Traditional DOEs based on propagation phase (or dynamic phase) lead to undesirable trade-offs between the angular /spectral bandwidths and diffraction efficiency of the primary order. Geometric phase elements realized by liquid crystals (LCs) have recently been applied to provide competitive solutions. However, due to the challenges of rigorous modeling, model-based design and high-quality fabrication, subwavelength feature size and nonlinear phase profile have not been systematically studied for these elements, which limits their applications. The goal of this dissertation is to overcome those design and fabrication challenges and realize novel LC geometric phase holograms (GPHs) for conventional and emerging applications. We develop rigorous numerical models to simulate LC alignment and electromagnetic response of GPHs. Simulation methods based on elastic continuum theory (ECT), finite-difference time-domain (FDTD) and rigorous coupled-wave analysis (RCWA) are implemented. For the first time, we apply the RCWA for polarization gratings and demonstrate its great advantage in accuracy and efficiency compare to other numerical methods. We also have first ever experimentally realized subwavelength Bragg regime polarization gratings (PGs) for visible light with periods down to 335 nm. These Bragg PGs manifest nearly 100% efficiency, larger angular/spectral bandwidths compared to traditional counterparts. Moreover, we have further broadened the angular bandwidth by layering multiple single-slant Bragg PGs in a monolithic film that manifests 40 angular bandwidth and 76% average efficiency within the bandwidth. To demonstrate the potential of nonlinear GPHs for wavefront shaping, we design and realize computer-generated far-field and near-field geometric phase holograms with a direct-write patterning system. We characterize the reconstructed image of the holograms and verify excellent agreement with our analysis based on scalar diffraction theory. We further focus on the design of both film parameters and phase profiles for various GPHs. Different optical models are investigated and applied for design including wave-based, ray-based and mixed implementations. As an example, an aspheric geometric phase doublet was designed with the ray model and 60% improvement of off-axis performance was demonstrated. This dissertation research firstly predicts and experimentally demonstrates unique properties of GPHs with subwavelength scale. Secondly it applies model-based design methods for GPHs with nonlinear phase profiles and multi-twist structures. It enables highthroughput, efficient and steep light deflection and arbitrary wavefront shaping with lowcost planar optical elements. At the end, we summarize the results and provide suggestions for future research.Subjects--Topical Terms:

517925
Optics.

Model-Based Design and Fabrication of Subwavelength and Nonlinear Geometric Phase Holograms.
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035 $a AAI11017887
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100 1 $a Xiang, Xiao. $3 3430875
245 1 0 $a Model-Based Design and Fabrication of Subwavelength and Nonlinear Geometric Phase Holograms.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2018
300 $a 139 p.
500 $a Source: Dissertation Abstracts International, Volume: 79-06(E), Section: A.
500 $a Advisers: Michael Kudenov; Keith Weninger; David Aspnes; Michael Escuti.
502 $a Thesis (Ph.D.)--North Carolina State University, 2018.
520 $a Efficiently deflecting light into large angles is important for various applications including beam steering, spectroscopy, optical communication and the emerging wearable displays for virtual/augmented reality (VR/AR) systems. Another important demand for many optical systems is arbitrary and accurate wavefront shaping by a monolithic and low-cost element. Compared to refractive elements, diffractive optical elements (DOEs) provide compact and lightweight solutions. One of the challenges is achieving wide angular acceptance, high efficiency and large deflection angle. Traditional DOEs based on propagation phase (or dynamic phase) lead to undesirable trade-offs between the angular /spectral bandwidths and diffraction efficiency of the primary order. Geometric phase elements realized by liquid crystals (LCs) have recently been applied to provide competitive solutions. However, due to the challenges of rigorous modeling, model-based design and high-quality fabrication, subwavelength feature size and nonlinear phase profile have not been systematically studied for these elements, which limits their applications. The goal of this dissertation is to overcome those design and fabrication challenges and realize novel LC geometric phase holograms (GPHs) for conventional and emerging applications. We develop rigorous numerical models to simulate LC alignment and electromagnetic response of GPHs. Simulation methods based on elastic continuum theory (ECT), finite-difference time-domain (FDTD) and rigorous coupled-wave analysis (RCWA) are implemented. For the first time, we apply the RCWA for polarization gratings and demonstrate its great advantage in accuracy and efficiency compare to other numerical methods. We also have first ever experimentally realized subwavelength Bragg regime polarization gratings (PGs) for visible light with periods down to 335 nm. These Bragg PGs manifest nearly 100% efficiency, larger angular/spectral bandwidths compared to traditional counterparts. Moreover, we have further broadened the angular bandwidth by layering multiple single-slant Bragg PGs in a monolithic film that manifests 40 angular bandwidth and 76% average efficiency within the bandwidth. To demonstrate the potential of nonlinear GPHs for wavefront shaping, we design and realize computer-generated far-field and near-field geometric phase holograms with a direct-write patterning system. We characterize the reconstructed image of the holograms and verify excellent agreement with our analysis based on scalar diffraction theory. We further focus on the design of both film parameters and phase profiles for various GPHs. Different optical models are investigated and applied for design including wave-based, ray-based and mixed implementations. As an example, an aspheric geometric phase doublet was designed with the ray model and 60% improvement of off-axis performance was demonstrated. This dissertation research firstly predicts and experimentally demonstrates unique properties of GPHs with subwavelength scale. Secondly it applies model-based design methods for GPHs with nonlinear phase profiles and multi-twist structures. It enables highthroughput, efficient and steep light deflection and arbitrary wavefront shaping with lowcost planar optical elements. At the end, we summarize the results and provide suggestions for future research.
590 $a School code: 0155.
650 4 $a Optics. $3 517925
690 $a 0752
710 2 $a North Carolina State University. $3 1018772
773 0 $t Dissertation Abstracts International $g 79-06A(E).
790 $a 0155
791 $a Ph.D.
792 $a 2018
793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=11017887