Modulating Light-Matter Interactions by Quantum Engineering of 2D Materials for Optoelectronics Devices

The study of light-matter interactions has undergone remarkable transformations over the past century, evolving from classical electrodynamics to modern-day nanophotonics. The advent of two-dimensional (2D) materials has revolutionized this field, enabling the confinement and manipulation of light at scales previously thought impossible. From the discovery of graphene to the exploration of hexagonal boron nitride (hBN) and transition metal dichalcogenides (TMDs), 2D materials have unlocked novel polaritonic phenomena, including plasmon, phonon, and exciton-polaritons. These quasiparticles facilitate sub-wavelength optical confinement, surpassing the diffraction limit and offering new opportunities for photonic applications. Building upon these advancements, this thesis explores the intricate physics of polaritonic modes in 2D materials, with a strong emphasis on Bound States in the Continuum (BICs), topological photonics, and ultraconfined resonances. We begin by establishing the fundamental principles governing phonon, plasmon, and exciton-polaritons in 2D materials. The concept of BICs is then introduced, highlighting their role in achieving lossless optical states and their emergence in hexagonal boron nitride (hBN) within the Reststrahlen bands. Our investigation delves into long-range coupled BICs in the Upper Reststrahlen Band (RB-2) and symmetry-protected topological BICs in the Lower Reststrahlen Band (RB-1), demonstrating their potential in enhancing optical robustness and waveguiding capabilities. Beyond BICs, this thesis explores ultraconfined dielectric resonances in hBN, specifically at frequencies beyond the transverse optical phonon frequency, revealing new regimes of light confinement. The impact of substrate engineering is also examined, where nanolaminate oxide layers enable sub-nanometer phonon-polariton confinement, further expanding the design space for 2D material-based photonics. To experimentally validate these findings, we employ advanced nanofabrication techniques, including electron beam lithography and atomic layer deposition, ensuring precise realization of theoretical predictions. As photonics continues to evolve, the principles outlined in this thesis will serve as a cornerstone for designing future material platforms capable of extreme light confinement and tailored wave interactions.