ORCID

https://orcid.org/0000-0001-7061-0099

Date of Award

5-8-2025

Author's School

Graduate School of Arts and Sciences

Author's Department

Chemistry

Degree Name

Doctor of Philosophy (PhD)

Degree Type

Dissertation

Abstract

Free-space optical communication holds immense potential for surpassing the bandwidth limitations of conventional physically defined channels. Achieving flexible and efficient communication in free space requires compact, robust optical components capable of dynamically tuning laser light without relying on bulky lenses or mechanically driven mirrors. Metasurfaces, or flat optics, have garnered significant attention due to their densely arranged subwavelength nano-resonators, which impart phase, amplitude, and polarization changes comparable to those of traditional bulky optics. However, conventional phase gradient metasurfaces are constrained by passive designs based on geometric configurations and the weak light-matter interaction inherent in most dielectric materials, limiting their applicability in spatial light modulation. Enhancing the resonance within nanoantennas to amplify far-field radiation and strengthen light-matter interaction is crucial for achieving efficient dynamic tunability. This thesis presents a highly tunable, energy-efficient, subwavelength-resolved reconfigurable phase gradient metasurface with a high-quality factor (high-Q). First, we demonstrate a prototypical meta-reflect-array platform functioning as a universal wavefront modulator. This platform achieves arbitrary high-Q resonances and amplified near-field distributions, both theoretically and experimentally. Phase modulation is realized by translating wavelength-dependent phase shifts into highly sensitive, geometry-dependent shifts at resonant wavelengths. A full 2π phase gradient is achieved with less than 2.6% volume fraction variation in a single antenna. The unique circular radiation pattern, dictated by high-Q dipolar guided mode resonance (DGMR), offers a new universal design for wavefront engineering. Additionally, we propose a novel strategy to eliminate strong coupling between high-Q DGMR antennas within the meta-reflect-array, addressing the fundamental trade-off between the Q-factor and antenna spacing. By introducing anisotropic fins between neighboring high-Q antennas, we selectively enhance the weaker longitudinal polarization component, leading to complete destructive interference with the transverse component. This results in total decoupling of neighboring structures, regardless of their spacing or Q-factor, enabling higher resolution wavefront shaping for applications such as low-power LiDAR, compact AR/VR systems, and dense-resonator metasurfaces for nonlinear optics, nonreciprocal devices, biosensing, and laser beam transmission. Building on this universal platform, we explore its programmability using external electrical inputs. A high-Q phase gradient metasurface amplitude display, featuring low energy consumption and high tuning efficiency, is demonstrated. By leveraging the high sensitivity of the antennas to subtle refractive index changes, we integrate resistive heating Ni wires with gates atop the antennas, achieving thermo-optically programmable shifts with less than 5 V. This platform supports integration into portable amplitude displays, compact LiDAR modules, and augmented reality (AR) and virtual reality (VR) glasses, highlighting its relevance for next-generation mobile and wearable optical systems. Finally, we integrate other active thin-film optical materials onto our universal platform to harness their novel optoelectronic properties. Within the strongly enhanced optical field of the high-Q nanoantennas, materials such as single-layer graphene are primarily explored to unlock their full potential in dynamic optoelectronic applications.

Language

English (en)

Chair and Committee

Bryce Sadtler

Committee Members

Mark Lawrence; Matthew Lew; Richard Mabbs; Sophia Hayes

Download

Share

COinS