Scalable Focused Ion Beam Creation of Nearly Lifetime-Limited Single Quantum Emitters in Diamond Nanostructures

The controlled creation of defect center---nanocavity systems is one of the outstanding challenges for efficiently interfacing spin quantum memories with photons for photon-based entanglement operations in a quantum network. Here, we demonstrate direct, maskless creation of atom-like single silicon-vacancy (SiV) centers in diamond nanostructures via focused ion beam implantation with $\sim 32$ nm lateral precision and $< 50$ nm positioning accuracy relative to a nanocavity. Moreover, we determine the Si+ ion to SiV center conversion yield to $\sim 2.5\%$ and observe a 10-fold conversion yield increase by additional electron irradiation. We extract inhomogeneously broadened ensemble emission linewidths of $\sim 51$ GHz, and close to lifetime-limited single-emitter transition linewidths down to $126 \pm13$ MHz corresponding to $\sim 1.4$-times the natural linewidth. This demonstration of deterministic creation of optically coherent solid-state single quantum systems is an important step towards development of scalable quantum optical devices

Quantum interference of electromechanically stabilized emitters in nanophotonic devices

Photon-mediated coupling between distant matter qubits may enable secure communication over long distances, the implementation of distributed quantum computing schemes, and the exploration of new regimes of many-body quantum dynamics. Nanophotonic devices coupled to solid-state quantum emitters represent a promising approach towards realization of these goals, as they combine strong light-matter interaction and high photon collection efficiencies. However, the scalability of these approaches is limited by the frequency mismatch between solid-state emitters and the instability of their optical transitions. Here we present a nano-electromechanical platform for stabilization and tuning of optical transitions of silicon-vacancy (SiV) color centers in diamond nanophotonic devices by dynamically controlling their strain environments. This strain-based tuning scheme has sufficient range and bandwidth to alleviate the spectral mismatch between individual SiV centers. Using strain, we ensure overlap between color center optical transitions and observe an entangled superradiant state by measuring correlations of photons collected from the diamond waveguide. This platform for tuning spectrally stable color centers in nanophotonic waveguides and resonators constitutes an important step towards a scalable quantum network

Aggregation-Induced Emission from Fluorophore–Quencher Dyads with Long-Lived Luminescence

Aggregation-induced emission (AIE) is an important photophysical phenomenon in molecular materials and has found broad applications in optoelectronics, bioimaging, and chemosensing. Currently, the majority of reported AIE-active molecules are based on either propeller-shaped rotamers or donor–acceptor molecules with strong intramolecular charge-transfer states. Here, we report a new design motif, where a fluorophore is covalently tethered to a quencher, to expand the scope of AIE-active materials. The fluorophore–quencher dyad (FQD) is nonemissive in solutions due to photoinduced electron-transfer quenching but becomes luminescent in the solid state. The intrinsic emission lifetimes are found to be within the microseconds domain at both room and low temperatures. We performed single-crystal X-ray diffraction measurement for each of the FQDs as well as theoretical calculations to account for the possible origin of the long-lived AIE. These FQDs represent a new class of AIE-active molecules with potential applications in organic optoelectronics

Aromatic Difluoroboron β‑Diketonate Complexes: Effects of π‑Conjugation and Media on Optical Properties

Aromatic difluoroboron β-diketonate complexes (BF₂bdks) are classic fluorescent molecules that have been explored as photochemical reagents, two-photon dyes, and oxygen sensors. To gain a better understanding of their emissive properties in both solution and polymer matrices, BF₂bdks with varying aromatic groups were synthesized and their photophysical properties were investigated in both methylene chloride and poly­(lactic acid) (PLA). Absorption spectra showed systematic variations that are well correlated with structural features, including the size of the aryl substituent and the presence of a para electron-donating methoxy substituent. Computational modeling of the absorption spectra with the TD-B3LYP/6-311+G­(d)//B3LYP/6-31G­(d) formulation of density functional theory and a polarizable continuum model of dichloromethane solvent shows that all systems show intense π–π* one-electron excitations, usually from one of the highest occupied molecular orbitals (HOMO – <i>k</i>, <i>k</i> = 0, 1, 2) to the lowest unoccupied molecular orbital (LUMO). Emission properties are sensitive to the dye structure and medium. Based on spectroscopic and lifetime studies, BF₂bdks exhibit comparable fluorescence properties in both solutions and polymers when the diketonate group is functionalized with smaller aromatic ring systems such as benzene. For BF₂bdks with larger arene ring systems, such as anthracene, emission from a strong intramolecular charge-transfer (ICT) state was also noted in both solution and in PLA. There are differences in relative intensities of peaks arising from π–π* and ICT excitations depending upon dye loading in PLA. Substituent effects were also observed. Electron-donating methoxyl groups on the aromatic rings lead to enhanced fluorescence quantum yields. For certain dyes, phosphorescence is detected at low temperature or under a nitrogen atmosphere in PLA matrices

All-optical nanoscale thermometry with silicon-vacancy centers in diamond

International audienc

Tailoring Oxygen Sensitivity with Halide Substitution in Difluoroboron Dibenzoylmethane Polylactide Materials

The dual-emissive properties of solid-state difluoroboron β-diketonate-poly­(lactic acid) (BF₂bdkPLA) materials have been utilized for biological oxygen sensing. In this work, BF₂dbm­(X)­PLA materials were synthesized, where X = H, F, Cl, Br, and I. The effects of changing the halide substituent and PLA polymer chain length on the optical properties in dilute CH₂Cl₂ solutions and solid-state polymer films were studied. These luminescent materials show fluorescence, phosphorescence, and lifetime tunability on the basis of molecular weight, as well as lifetime modulation via the halide substituent. Short BF₂dbm­(Br)­PLA (6.0 kDa) and both short and long BF₂dbm­(I)­PLA polymers (6.0 or 20.3 kDa) have fluorescence and intense phosphorescence ideal for ratiometric oxygen sensing. The lighter halide-dye polymers with hydrogen, fluorine, and chlorine substitution have longer phosphorescence lifetimes and can be utilized as ultrasensitive oxygen sensors. Photostability was also analyzed for the polymer films