Silicon Carbide Phonon Polaritonic metasurfaces for an active control of mid-infrared light

Date

2022-08

Journal Title

Journal ISSN

Volume Title

Publisher

Abstract

The objective of this dissertation is to understand the near-field polaritonic interaction between mid-infrared surface waves and surface polarized ion oscillations confined in subwavelength-scale metasurfaces and to the further development of tunable and reconfigurable surface polaritonic metasurfaces for dynamic control of mid-infrared surface waves. Optical metasurfaces have been used to demonstrate a wavefront control of light in free space and optical waveguides by imposing spatially varying optical responses to the light. However, controlling light localized and propagating on the surface has been challenging because the surface waves scatter intensively to the metallic metasurfaces causing optical power loss. In this thesis work, we chose silicon carbide (SiC), one of the standard polar dielectrics in mid-infrared, as an emerging metasurface platform showing low optical power loss and high coupling efficiency to the light. Here, we propose and experimentally demonstrate passive and active resonant nanocavities that enhance the absorption spectrum and dynamically control the resonance frequency. The passive device is designed with the subwavelength-scale (≈ λ0/150) resonant nanocavity arrays enhance the device's absorption spectrum in the mid-infrared (10 – 12 microns) via excitation of coupled surface plasmon-phonon polaritons. The proposed metal-insulator-polar dielectric (gold-silicon-silicon carbide) structure supports a guided mode of the coupled surface polaritons in the lateral direction while vertically confining the mid-infrared wave within the 80 nm thick dielectric spacer. In particular, 0/10 scale metal-insulator gratings are imposed to form Fabry-Pérot cavity arrays displaying angle-insensitive and frequency-tunable absorption of up to 80% of the optical power in the mid-infrared. We have fabricated resonant optical nanocavity with gold-silicon multilayer grating structures on 6H-Silicon for different cavity widths. We measured the strong and well-defined absorption spectrum via excitation of coupled surface plasmon-phonon polaritons. Experimental results agreed with the analytical and numerical study results. Our work should benefit diverse mid-infrared applications and novel designs of polariton-based spectral devices in the future. Reconfigurable nanostructures are rarely achievable due to the lack of proper active materials suitable for polar dielectrics. Using a subwavelength nanostructure based metal-insulator phase transition material, vanadium dioxide (VO2), we designed and experimentally demonstrated the active and reconfigurable device. We fabricated metal (gold) grating structures on phase transition material (vanadium dioxide) layer on polar dielectric (silicon carbide). We experimentally studied dynamic control cavity modes of propagating SPhP resonances with respect to the temperature, which is agreed with the numerical simulations. Propagating SPhP resonance frequencies rely on optical index of nanocavity which can be tuned by the metal-insulator phase transition of VO2. We observed reflection spectrum under the normal incidence of polarized light in the Reststrahlen band of SiC (10-12 microns wavelength) and temperature dependent resonance shift by heating up the device. Increase in the temperature increase the complex index of the VO2 results the SPhP resonance weak and shifts over a range of 30 wavenumber. At the insulator-metal transition temperature VO2 become more lossy metal which destroy the SPhP resonances. Reconfigurable and active resonant cavity will benefit long-wave infrared control of fundamental optical processes including absorption, rewritable data storage, spatial control of the light using tunable optical antennas, phase change switches, and active metasurfaces.


Embargo status: Restricted to TTU community only. To view, login with your eRaider (top right). Others may request the author grant access exception by clicking on the PDF link to the left.

Description

Keywords

Metasurfaces, Phonon Polaritonic Metasrufaces, Silicon Carbide, Active Control of Mid-Infrared Light, Reconfigurable Nanostructures, Vanadium Dioxide, SPP-SPhP Coupled Mode, Phase Transition Material, Fabry-Perot Nanocavity, SPhP Resonance, Active Control of SPhP Resonances, Active Metasurface

Citation