Dynamically Tunable Light-Matter Interactions in Low-Dimensional Material Integrated Nanophotonics

Abstract

Due to their small mode volumes and strong electromagnetic field confinement, photonic crys- tal cavities provide an exceptional platform for enhancing light–matter interactions. These interactions have been extensively investigated using conventional emitters such as quan- tum dots and crystal defects. More recently, two-dimensional (2D) van der Waals materials, particularly transition metal dichalcogenides (TMDs) and magnetic semiconductors such as Chromium Sulfide Bromide (CrSBr), have emerged as promising emitters owing to their rich excitonic properties, enabling phenomena including exciton-polaritons, enhanced photolumi- nescence, and single-photon emission. However, integrating 2D materials with nanophotonic cavities remains challenging because fabrication and transfer processes frequently introduce spectral detuning between the emitter and cavity resonance. This mismatch is commonly ad- dressed through iterative fabrication and trial-and-error optimization, limiting reproducibil- ity and scalability.This dissertation investigates dynamic approaches for overcoming resonance detuning in integrated nanophotonic platforms. It first explores mechanical strain as a means of tuning the optical resonances of WSe2. Subsequently, we introduce a nondestructive, reversible, and reproducible tuning mechanism to counteract detuning, based on the magnetic properties of CrSBr. This approach addresses several of the limitations associated with strain-based approaches. Beyond external tuning mechanisms, this dissertation examines spatial confinement as an additional strategy for tailoring light–matter interactions. In conventional low-dimensional semiconductor systems, including quantum dots, nanowires, and quantum wells, quantum confinement requires dimensions comparable to the exciton Bohr radius, making precise nanoscale fabrication essential. In contrast, exciton-polaritons possess ultralight effective masses and correspondingly large de Broglie wavelengths, enabling quantum confinement within micron-scale potentials that are substantially easier to realize experimentally. By patterning CrSBr, a high refractive index material that support self-hybridized exciton- polaritons, we are able to observe quantum confinement at larger confinement scales. This dissertation establishes versatile approaches for dynamically tuning and controlling light–matter interactions in low-dimensional material integrated nanophotonic devices.