Jonathan D. Hood

CsPbI3 nanocrystals exhibit bright, tunable photoluminescence and are attractive for use in a variety of optoelectronic devices. Existing colloidal syntheses of CsPbI3 predominantly produce nanocubes or other hexahedral shapes because of the stability of the nanocube facets in the perovskite structure. In this work, we utilize a bidentate ammonium ligand with a tunable linker between the two head groups in order to preferentially nucleate and stabilize rhombic dodecahedral nanocrystals. These particles show enhanced environmental stability compared to CsPbI3 nanocrystals capped with monodentate ammonium ligands and self-assemble into ordered, hexagonally packed monolayers. This work represents a new entry into the limited shape catalog of CsPbI3 and expands the design principles for facet-selective ligands in lead-halide perovskite nanocrystals.

Organic molecules embedded in an organic matrix exhibit lifetime-limited optical coherence and bright emission at cryogenic temperatures below 3 K. Here, we present a simple vapor-phase growth method for synthesizing optically thin DBT-doped anthracene crystals that are compatible with integrated nanophotonics. The crystals are 200 nm thick with sub-nm surface roughness and a tunable lateral dimension of up to 200 μm. The molecular transitions remain narrow and spectrally stable, with inhomogeneous broadening below 100 GHz, comparable to DBT in bulk anthracene. The dopant density is tunable up to several hundred molecules per μm2, ensuring emitters within the near-field of nanophotonic structures. We demonstrate that the crystals can be micropositioned onto integrated photonic devices with the molecular dipole aligned to the optical mode. This approach opens a path toward on-chip single-photon sources and collective many-emitter effects.

Dibenzoterrylene (DBT) is a coherent molecular single-photon emitter that exhibits an interesting energetic landscape with multiple low-energy, accessible conformations. In this work, using first principle approaches, we systematically investigate the conformational landscape of DBT in the gas phase, identifying five unique conformers, four of which are expected to be thermally accessible in a solid state host. We further analyze vibrational and electronic spectroscopies to identify conformer-specific spectral signatures. We find that each conformer exhibits largely similar spectral features in both vibrational and electronic spectroscopies; however, subtle differences exist across all spectra, which highlight possible conformer-specific changes that may be able to be identified in high-resolution spectroscopic experiments. Finally, we explore the Franck–Condon–Herzberg–Teller vibrationally resolved electronic excitation spectrum which showcases even more rich conformation-specific landmarks. Collectively, our results provide a comprehensive framework for understanding how DBT’s conformer-specific electronic structure could play a role in observed optical behaviors.

Realizing robust many-body exciton interactions, coherence, and long-range exciton transport is central to technologies ranging from quantum information science (QIS) to light-emitting devices and solar cells. Colloidal quantum dots (QDs) offer scalable fabrication and spectral tunability, yet performance is suppressed by inhomogeneous broadening, defects, and fast dephasing. Lead-halide perovskite QDs, exhibiting large transition dipole moments, high radiative efficiencies, and slow low-temperature dephasing, enable strong light-matter coupling and long-range dipolar exciton-exciton interactions. This review focuses on the origins and consequences of many-body exciton physics in perovskite QDs, including dipole-mediated interactions and cooperative radiative phenomena. We discuss how exciton fine structure, inter-QD electronic coupling, and exciton-phonon interactions govern coherence and the role of disorder. We then examine exciton transport in QD solids, emphasizing the crossover from coherent motion enabled by delocalized excitonic wave functions to dephasing-driven incoherent hopping. Finally, we survey routes toward scalable many-body states through nanophotonic integration.

We present a hybrid solid-state cavity quantum electrodynamics (QED) platform that integrates a high density of coherent organic molecules with high-quality-factor nanophotonics. Thin anthracene crystals doped with dibenzoterrylene (DBT) are mechanically transferred onto prefabricated silicon nitride photonic crystal cavities, preserving both the cavity quality and molecular coherence. This approach decouples emitter synthesis from nanofabrication, providing a pathway for integrating other types of emitters. The high density of molecular emitters results in up to ten molecules being coupled to a single cavity. By tuning pairs of molecules into resonance within a single cavity mode, we observe cavity-mediated interactions in both dispersive and dissipative regimes. These results establish an accessible route to deterministic on-chip single- and multiphoton sources.

We implement permanent spectral tuning to bring lifetime-limited emitters into collective resonance within an integrated photonic cavity. This addresses a fundamental challenge in solid-state cavity QED: combining multiple coherent quantum emitters with scalable nanophotonics. Our hybrid approach decouples emitter synthesis from nanophotonic fabrication using straightforward techniques that make cavity QED broadly accessible. High doping densities allow us to couple several coherent emitters to a single cavity mode, while optically-induced frequency shifting provides long-lived spectral control. By tuning two molecules into resonance, we demonstrate controlled formation of collective quantum states, establishing a scalable platform for many-body cavity QED. This opens pathways toward chemically-designed quantum systems where optical properties are engineered through synthetic chemistry.

We demonstrate background-free imaging and sideband cooling of a single 133Cs atom via the narrow-line 6S1/2 to 5D5/2 electric quadrupole transition in a 1064 nm optical tweezer. The 5D5/2 state decays through the 6P3/2 state to the ground state, emitting an 852 nm wavelength photon that allows for background-free imaging. By encoding both spin and orbital angular momentum onto the 685 nm excitation light, we achieve background-free fluorescence histograms with 99.58(3)% fidelity by positioning the atom at the dark center of a vortex beam. Tuning the tweezer polarization ellipticity realizes a magic trap for the stretched F = 4, mF = 4 to F' = 6, mF' = 6 cycling transition. We cool to 5 uK in a 1.1 mK trap and outline a strategy for ground-state cooling. We compare cooling performance across different sideband regimes, while also exploring how the orbital angular momentum of structured light controls the selection rules for quadrupole transitions. These results expand the toolbox for high-fidelity quantum control and cooling in alkali-atom tweezer arrays.