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Controlling the Flow of Light Using High-Contrast Metastructures


Horie, Yu (2018) Controlling the Flow of Light Using High-Contrast Metastructures. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z94X5604.


A new class of planar optical components and devices has emerged using subwavelength metastructures with a strong contrast in refractive indices. High-contrast metastructures have shown promises to manipulate optical fields in an extraordinary way and to replace conventional bulky optical elements by their low-profile analogs, typically with subwavelength-scale features. We elucidate the underlying principle, how these seemingly low-profile geometries render unique optical responses, using the coupled-mode analysis in a multimode waveguide. Moreover, strong field localization in high-index structures allows us to interpret each single element in the metastructures as a low-quality-factor resonator (or a localized scatterer), permitting us to realize designer surface that shapes phase, amplitude, and polarization of light in free space, also known as an optical metasurface. The remainder of the thesis is devoted to explore novel applications in optics using high-contrast metastructures. One of the particularly interesting applications is to use them in an optical resonator. Specifically, we demonstrate to incorporate high-contrast subwavelength grating reflectors and dielectric metasufaces in a vertical Fabry–Perot cavity, and show that we can flexibly tune the resonance frequency by the subwavelength patterning. With this technique, we envision the realization of compact, on-chip spectrometers when integrating them on a photodetector array. Secondly, we investigate the use of high-contrast subwavelength gratings in visible wavelengths. We perform the optimization of their geometries and demonstrate a set of RGB color filters, down to near a micrometer in the pixel size. This platform exhibits unique performances such as high efficiency, angular insensitivity, and color tunability by the design. A novel device concept is also explored, where a high-contrast subwavelength grating reflector is integrated on a silicon platform to constitute an active resonant antenna, enabling high-speed, phase-dominant modulation by means of thermo-optic effect of silicon. We demonstrate an array of such active antennas, yielding a beam deflection capability. This justifies the robustness of our device design, enabling a large-scale integration of high-speed, phase-dominant spatial light modulators. Finally, we introduce a disorder-engineered metasurface in the context of wavefront shaping. Recently, wavefront shaping with disordered media has demonstrated optical manipulation capabilities beyond those of conventional optics, but translating this class of technology into a practical use has remained challenging due to enormous amounts of information needed to be characterized as the input-output responses. As a paradigm shift, we propose the use of disorder-engineered metasurface in wavefront shaping, where the disorder is programmatically designed and makes the system characterization-free prior to use. With this approach, we demonstrate high numerical aperture focusing in an extended volume as well as wide-field fluorescence imaging with unprecedented performances.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Optics, Photonics, Nanophotonics
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Electrical Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Faraon, Andrei
Group:Kavli Nanoscience Institute
Thesis Committee:
  • Faraon, Andrei (chair)
  • Emami, Azita
  • Hajimiri, Ali
  • Vahala, Kerry J.
  • Yang, Changhuei
Defense Date:17 August 2017
Non-Caltech Author Email:horie.u (AT)
Funding AgencyGrant Number
Defense Advanced Research Projects Agency (DARPA)UNSPECIFIED
National Science Foundation1512266
U.S. Department of Energy, Office of Science, Office of Basic Energy SciencesDE-SC0001293
Record Number:CaltechTHESIS:09202017-124555409
Persistent URL:
Related URLs:
URLURL TypeDescription for part of Chapter 1. for part of Chapter 2. for part of Chapter 2. for Chapter 3. for Chapter 5.
Horie, Yu0000-0001-7083-1270
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:10442
Deposited By: Yu Horie
Deposited On:25 Sep 2017 22:57
Last Modified:04 Oct 2019 00:17

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