Plasmonic Metasurface for Visible Hologram and Electrically Tunable Devices
Date Issued
2015
Date
2015
Author(s)
Huang, Yao-Wei
Abstract
Nowadays, vision technologies in various color applications are primarily targeting the three primary colors and their mixing in conjunction with control of light polarization. The scalar diffractive pattern of liquid crystal displays (LCD) or digital micro-mirror devices (DMD) employed in hologram renders polarization unswitchable. The metamaterials or metasurfaces employed surface electromagnetic wave are capable of shaping both amplitude phase and polarization of light over subwavelength length scales. They have been previously applied to broadband and broad-angle phase hologram with polarization-dependent images but failed to yield color multiplexing in the visible spectrum. In contrast, light information can be manipulated either in amplitude, phase, polarization, or frequency, and combination thereof. Chip based hybrid-plasmonic modulators made of incorporating nanoscale plasmonics and classic photonic elements has the fasted modulation speed and lowest energy-per-signal are proposed to overcome a limited propagation length and higher loss of a surface plasmon-polariton (SPP) mode. Metasurfaces composed of sub-wavelength artificial structures show promise for extraordinary light-manipulation and development of ultrathin optical components over a broad range of the electromagnetic spectrum. However structures developed to date do not allow for post-fabrication control of antenna properties. Metasurfaces incorporating dynamically tunable methods offer the unprecedented opportunities in reconfigurable flat optical devices. In this dissertation, a phase modulated multi-color meta-hologram (MCMH) and an electrically gate-tunable metasurface were design and investigated. The MCMH made of sandwich structure of Al-nanorod/SiO2/Al-mirror arranged in a two-dimensional array of pixels is polarization-dependent and capable of producing images in three primary colors. With proper design of the structure, we obtain resonances of narrow bandwidths to allow for implementation of the multi-color scheme. Experimental reflected spectrum for each kind of nanorods array are investigated, which is in agreement with the simulation results and certainly lead to full color applications using color mixing. We have investigated the integration of the transparent conductor indium tin oxide (ITO) active elements to realize gate-tunable phased arrays of subwavelength antenna in a reflectarray metasurface configuration to enable gate-tunable permittivity. The magnetic dipole resonance of each antenna interacts with the carrier density-dependent permittivity resonance of the ITO to enable phase and amplitude tunability. A multiphysics method incorporated semiconductor physics and electromagnetic waves are considered in the design and resonance analysis. A simple 2-level dynamic phase grating is investigated using the gate-tunable metasurface. With different applied biases, the controllable diffraction patterns have been investigated by dynamic phase grating system. This work provides a general design principle applicable to dynamic metasurface devices based on gate-tunable field effect.
Subjects
Metamaterials
metasurfaces
plasmonics
meta-hologram
holography
nanoantennas
transparent conducting oxide
electrically tunable
field-effect modulation
Type
thesis
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