Integration of 2D Semiconductors and Hexagonal Boron Nitride as a Platform For Future Quantum Photonics

This report presents research conducted by Samuel W. LaGasse as part of a Jerome and Isabelle Karle Distinguished Scholar Fellowship between November 2021 and 2022. This work investigates the optical properties of layered 2D materials with a focus on gaining control over them in two ways (1) by electrostatic gating and (2) by a novel waveguiding approach. The major output of this fellowship is fundamental knowledge of factors governing atomically thin semiconductors (transition metal dichalcogenides, or TMDs) embedded in slabs of insulating hexagonal boron nitride (hBN). Monolayer TMDs host excitons that behave as either in-plane and out-of-plane optical dipoles. The intricate coupling of such dipoles to slab waveguide modes of hBN is elucidated. The usage of such slab waveguides is further characterized with Fourier spectroscopy, highlighting how this approach can be used to study dipoles in layered materials. Electrostatic gating is used to tune the ratios of in-plane and out-of-plane dipoles, as well as the specific excitonic charge states which are observed. The slab waveguide approach leads to extremely high-quality optical samples, which have future applications as sensors or in quantum information. This work is the topic of a manuscript which is to be submitted in FY23.