Event

This dissertation explores the intersection of many-body physics and photonics. While the toolbox of photonics provides powerful means to probe, manipulate, and even simulate matter, insights from many-body physics can, in turn, guide the design of devices with desirable optical properties. In this pursuit, we use two complementary material platforms: (i) atomically-thin transition metal dichalcogenide (TMD) semiconductors, where strong excitonic interactions and moire superlattices enable emergent many-body phenomena; and (ii) CMOS-compatible silicon nitride photonic integrated circuits, where topology and nonlinearity give rise to a new regime of exploring topological photonic devices for practical applications.

(i) 2D semiconductors:
First, we propose and experimentally demonstrate a sub-wavelength two-dimensional nanocavity using two atomically thin TMD mirrors with degenerate resonances. Angle-resolved measurements show a flat band, which sets this system apart from conventional photonic cavities. We demonstrate how the excitonic nature of the mirrors enables the formation of chiral and tunable optical modes upon the application of an external magnetic field. Moreover, we show the electrical tunability of the confined mode. Our work demonstrates a mechanism for confining light with high-quality excitonic materials, opening perspectives for spin-photon interfaces, and chiral cavity electrodynamics.

Second, we explore the interplay between fermionic and bosonic populations, using a TMD heterobilayer device that hosts this hybrid particle density. We independently tune the fermionic and bosonic populations by electronic doping and optical injection of electron-hole pairs, respectively. This enables us to form strongly interacting excitons that are manifested in a large energy gap in the photoluminescence spectrum. Our system provides a controllable approach to the exploration of quantum many-body effects in the generalized Bose-Fermi-Hubbard model. Moreover, the study of excitonic diffusion in these devices paves the way for understanding the interaction between fundamental particles in such systems.

Third, we overcome the challenges of limited spatial resolution and the efficiency of light-matter interaction stemming from uniform and diffraction-limited free-space optics by using metasurface plasmon polaritons (MPPs) to form a sub-wavelength optical lattice on a TMD monolayer. Specifically, we report a two orders of magnitude more efficient ``nonlocal” pump-probe scheme where MPPs are excited to induce a spatially modulated AC Stark shift for excitons in a TMD monolayer, several microns away from the illumination spot. Moreover, we present a robust signature of MPP-induced periodic sub-diffraction modulation. Our results will allow exploring power-efficient light-induced lattice phenomena below the diffraction limit in active chip-compatible MPP architectures.

(ii) Photonic integrated circuits:
Finally, we design and experimentally investigate the field of topological nonlinear photonics on the industry-ready silicon nitride platform. These devices generate an exotic nested frequency comb with two independent timescales. Moreover, the nested lattice simultaneously generates ultrabroad bandwidth light in the fundamental-, second-, third-, and fourth-harmonic bands and achieves 100% wafer-scale device yield, without any post-fabrication tuning. Distinct spatial and spectral signatures confirm the predicted relaxation of frequency-phase matching, establishing a scalable route for chip-scale nonlinear optics. Our approach provides possibilities for integrated frequency conversion and synchronization, self-referencing, precision metrology, squeezed-light sources, and nonlinear optical computing.