Light Modulation with Vanadium Dioxide-Based Optical Devices

Citation

Kim, Yonghwi (2022) Light Modulation with Vanadium Dioxide-Based Optical Devices. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/pkxj-9584. https://resolver.caltech.edu/CaltechTHESIS:06232021-050358035

Abstract

This thesis focuses on active material-based tunable optical devices. In particular, I have been working on tunable optical devices based on vanadium dioxide (VO₂), which can produce tunable optical responses, such as amplitude, phase, thermal emission, and quantum emission. The modulations of light are achieved by coupling the phase-transition material with the precisely designed resonant structures or by placing it close to quantum emitters. This thesis presents three research streams, which aim at experimentally demonstrating the dynamically tunable optical responses using VO₂. First, we propose and experimentally demonstrate an electrically tunable VO₂-based reflectarray metasurface that exhibits largely tunable optical responses in the near-infrared region. We incorporate VO₂ directly into the plasmonic resonator, which undergoes a phase transition triggered by Joule heating. The induced plasmonic resonance modulation is accompanied by a large and continuous modulation in optical responses, such as amplitude, resonance wavelength, and phase. Second, we propose and demonstrate an active tuning of thermal emission from VO₂-based metasurfaces. We introduce a thin VO₂ film as an absorbing layer on top of a metal reflector. This layer is coupled with a dielectric resonator, with a dielectric spacer placed between them. Upon undergoing a phase transition triggered by heating, the induced absorption tuning of the VO₂ layer is accompanied by modulation in the absorption spectra of the coupled structure. We experimentally show narrowband absorption spectra, which can be tuned by controlling the VO₂ temperature. Finally, we experimentally demonstrate the axial position of quantum emitters in a multilayered hexagonal boron nitride (hBN) flake with nanoscale accuracy, which is enabled through the modification of a photonic density of states by introducing VO₂. Furthermore, we observe a sharp distance-dependent photoluminescence response by modulating the optical environment of an emitter placed close to the hBN/VO₂ interface.

Thesis Files