Degree

Doctor of Philosophy (PhD)

Department

Electrical and Computer Engineering

Document Type

Dissertation

Abstract

In this dissertation, we use a memetic optimization algorithm to inverse-design planar aperiodic multilayer structures which provide reconfigurable and nonreciprocal control of light and thermal radiation in the visible and infrared wavelength ranges.

We first introduce multilayer structures with the phase-change material Ge2Sb2Te5 (GST) for use as broadband switchable absorbers in the infrared wavelength range. We show that in the optimized structures near-perfect absorption can be switched to very low absorption in a broad wavelength range by switching GST from its crystalline to its amorphous phase. Our optimized lithography-free structures have better performance than harder-to-fabricate three-dimensional structures.

We introduce multilayer structures based on phase-change materials for reconfigurable structural color generation. Specifically, we design structures that generate either two or four maximally distinct structural colors. We demonstrate that our design approach achieves strong color contrast between the generated colors. Our results could lead to a new class of single-cell multicolor pixels which retain each color without power consumption, making them particularly appealing for low refresh rate displays.

We develop a switchable radiative cooling system composed of a spectrally selective band-pass filter positioned on top of a radiative cooler incorporating phase-change material. We perform two distinct and computationally demanding optimization objectives: one structure maximizes the net cooling power difference between the on and off states, and the second maximizes the temperature drop of the system below ambient in the on state while strictly suppressing radiative heat loss in the off state. Despite the fundamentally different optimization objectives and constraints, we discover that both designs converge to very similar optimized structures for both the cooler and the filter.

In the last part of this dissertation, we replace phase-change tunability with a different mechanism for controlling thermal radiation, namely nonreciprocity. Here, we present a systematic optimization framework for multilayer aperiodic structures based on Weyl semimetals that maximizes the nonreciprocal contrast over broad spectral and angular ranges. The strong broadband and wide-angle nonreciprocal response of the proposed planar, easy-to-fabricate structures highlights their potential in thermal photonic applications, including directional thermal emission, radiative energy control, thermophotovoltaics, and thermal management.

Date

8-20-2026

Committee Chair

Veronis, Georgios

LSU Acknowledgement

1

LSU Accessibility Acknowledgment

1

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