AbstractIntegration of quantum emitters in photonic structures is an important step in the broader quest to generate and manipulate on-demand single photons via compact solid-state devices. Unfortunately, implementations relying on material platforms that also serve as the emitter host often suffer from a tradeoff between the desired emitter properties and the photonic system practicality and performance. Here, we demonstrate “pick and place” integration of a Si3N4 microdisk optical resonator with a bright emitter host in the form of ∼20-nm-thick hexagonal boron nitride (hBN). The film folds around the microdisk maximizing contact to ultimately form a hybrid hBN/Si3N4 structure. The local strain that develops in the hBN film at the resonator circumference deterministically activates a low density of defect emitters within the whispering gallery mode volume of the microdisk. These conditions allow us to demonstrate cavity-mediated out-coupling of emission from defect states in hBN through the microdisk cavity modes. Our results pave the route toward the development of chip-scale quantum photonic circuits with independent emitter/resonator optimization for active and passive functionalities.

The silicon vacancy (SiV) center in diamond is typically found in three stable charge states, SiV0, SiV–, and SiV2–, but studying the processes leading to their formation is challenging, especially at room temperature, due to their starkly different photoluminescence rates. Here, we use confocal fluorescence microscopy to activate and probe charge interconversion between all three charge states under ambient conditions. In particular, we witness the formation of SiV0 via the two-step capture of diffusing, photogenerated holes, a process we expose both through direct SiV0 fluorescence measurements at low temperatures and confocal microscopy observations in the presence of externally applied electric fields. In addition, we show that continuous red illumination induces the converse process, first transforming SiV0 into SiV– and then into SiV2–. Our results shed light on the charge dynamics of SiV and promise opportunities for nanoscale sensing and quantum information processing.

Various properties of (CdSe) 3n clusters (n = 1−9) were obtained using computational techniques. Using a simple force field, a simulated annealing technique was employed to explore the potential energy landscape and identify the isomers available at low temperatures. The lowest energy isomer was then optimized using density functional theory, and the quantities associated with their stability and optoelectronics were calculated. The possibility of fluxionality for a given range of temperatures and solvents was characterized by computing thermodynamic properties and inherent structure energies. All studied systems give rise to energetically stable hollow structures composed of six-and fourmembered rings that changed from spherical to tubular as the number of atoms increased. For a solvent of dielectric constant equal to three, fluxionality was observed at 300 K for almost all clusters considered. The corresponding band gap was found to be ∼3 eV and relatively independent of the size of the clusters in this size range. The absorption coefficients (as calculated from the dielectric functions) obtained from fluxionality effects are in agreement with the experimental absorption profiles.

Color centers in hexagonal boron nitride (hBN) are presently attracting broad interest as a novel platform for nanoscale sensing and quantum information processing. Unfortunately, their atomic structures remain largely elusive and only a small percentage of the emitters studied thus far have the properties required to serve as optically addressable spin qubits. Here, we use confocal fluorescence microscopy at variable temperatures to study a new class of point defects produced via cerium ion implantation in thin hBN flakes. We find that, to a significant fraction, emitters show bright room-temperature emission, and good optical stability suggesting the formation of Ce-based point defects. Using density functional theory (DFT) we calculate the emission properties of candidate emitters, and single out the CeVB center—formed by an interlayer Ce atom adjacent to a boron vacancy—as one possible microscopic model. Our results suggest an intriguing route to defect engineering that simultaneously exploits the singular properties of rare-earth ions and the versatility of two-dimensional material hosts.