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Negative charge enhancement of near-surface nitrogen vacancy centers by multicolor excitation
摘要： Nitrogen vacancy (NV) centers in diamond have been identified over the past few years as promising systems for a variety of applications, ranging from quantum information science to magnetic sensing. This relies on the unique optical and spin properties of the negatively charged NV. Many of these applications require shallow NV centers, i.e., NVs that are close (a few nm) to the diamond surface. In recent years there has been increasing interest in understanding the spin and charge dynamics of NV centers under various illumination conditions, specifically under infrared (IR) excitation, which has been demonstrated to have significant impact on the NV centers’ emission and charge state. Nevertheless, a full understanding of all experimental data is still lacking, with further complications arising from potential differences between the photodynamics of bulk and shallow NVs. Here we suggest a generalized quantitative model for NV center spin- and charge-state dynamics under both green and IR excitation. We experimentally extract the relevant transition rates, providing a comprehensive model which reconciles all existing experimental results in the literature, except for highly nonlinear regimes. Moreover, we identify key differences between the photodynamics of bulk and shallow NVs, and use them to significantly enhance the initialization fidelity of shallow NVs to the useful negatively charged state.
关键词： nitrogen vacancy centers,recombination,shallow NVs,bulk NVs,photodynamics,green excitation,ionization,charge state,IR excitation,diamond
更新于2025-09-23 15:23:52
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Measuring the Lower Critical Field of Superconductors Using Nitrogen-Vacancy Centers in Diamond Optical Magnetometry
摘要： The lower critical magnetic field, Hc1, of superconductors is measured by optical magnetometry using ensembles of nitrogen-vacancy centers in diamond. The technique is minimally invasive and allows accurate detection of the vector magnetic field with subgauss sensitivity and submicrometer spatial resolution. These capabilities are used for detailed characterization of the first vortex penetration into superconducting samples from the corners. Aided by the revised calculations of the effective demagnetization factors of actual cuboid-shaped samples, these measurements provide precise determination of Hc1 and the related absolute value of the London penetration depth, λ. We apply this method to three well-studied superconductors: optimally doped Ba(Fe1?xCox)2As2, stoichiometric CaKFe4As4, and the high-Tc cuprate YBa2Cu3O7?δ. Our results compared well with the values of λ obtained with other techniques, thus adding another noninvasive and sensitive method to measure these important parameters of superconductors.
关键词： optical magnetometry,nitrogen-vacancy centers,London penetration depth,superconductors,lower critical field
更新于2025-09-23 15:22:29
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Fabrication of Two-Dimensional Arrays of Fluorescent Centers in Single-Crystalline Diamond Using Particle Beam Writing
摘要： Micrometer-scale patterning was performed using the particle beam writing technique with a focused heavy-ion microbeam, allowing the creation of a unique two-dimensional distribution of fluorescent centers in single-crystalline diamond. The focused nitrogen microbeam was scanned over the target of single-crystalline diamond prepared by chemical vapor deposition to create nitrogen-vacancy (NV) centers at defined positions. Imaging using a custom-built confocal fluorescence microscopy system revealed that the desired NV distribution was generated in the target crystal with a spatial resolution similar to the beam resolution. A two-dimensional matrix barcode test pattern was successfully generated in a diamond substrate to demonstrate the encryption of information inside a solid-state target.
关键词： diamond,particle beam writing,two-dimensional,chemical vapor deposition,nitrogen vacancy centers,confocal fluorescence microscopy
更新于2025-09-23 15:21:21
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Fluorescent Nanodiamonds || Producing Fluorescent Nanodiamonds
摘要： Natural diamonds in colors are commonly known as fancies, or fancy color diamonds, in gemstone industries. They are rare, beautiful, and some even carry impressive price tags in the jewelry market. By comparison, micro‐ and nanoscale diamond powders are low in price, with or without colors and fluorescent or not. These powders have been used as abrasives for grinding and polishing purposes since ancient time, mainly because of their extraordinary hardness. Little or no attention has been paid over the centuries to other properties of nanodiamonds such as their innate biocompatibility and light‐emitting capability. The invention of fluorescent nanodiamond (FND) in 2005 has revolutionized the field, opening a new area of research and development with diamonds. Experiments with FNDs in the last decade have demonstrated various promising applications of surface‐functionalized FNDs in diversified fields, ranging from physics and chemistry to biology and medicine. It is worthy of noting that as originated from the discovery of Radium by Marie Sk?odowska Curie (Section 3.2), FNDs may very well be called Madame Curie’s gemstones, valued appropriately as a scientist’s best friend.
关键词： fluorescent nanodiamonds,magnetically modulated fluorescence,fluorescence lifetime,size reduction,FND,ion irradiation,H3 centers,nitrogen-vacancy centers,electron irradiation,NV centers
更新于2025-09-23 15:21:01
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Efficient generation of nitrogen vacancy centers by laser writing close to the diamond surface with a layer of silicon nanoballs
摘要： We proposed a method to effectively fabricate negatively charged nitrogen vacancy (NV?) centers close to the diamond surface by applying femtosecond laser writing technique. With a thick layer of silicon (Si) nanoballs coated, diamond surface was irradiated by high-fluence femtosecond laser pulses. A large number of NV? centers were created around the laser ablation crater area without thermal annealing. The distribution of the NV? centers was expanded to about 50 μm away from the crater center. To demonstrate the function of Si nanoballs, we performed the exactly same laser illumination process on the bare region of the sample surface. In this case, only a few NV? centers were generated around ablation crater. At distance of 32 μm away from crater centers, the NV? density for the case with nanoballs was up to 15.5 times higher compared to the case without nanoballs. Furthermore, we also investigated the influence of laser fluence and pulse number on the NV? density for the case with Si-nanoball layer. Finally, the formation mechanism of NV? centers and the role of Si nanoballs were explained via Coulomb explosion model. The method is demonstrated to be a promising approach to efficiently and rapidly fabricate NV? centers close to the surface of the diamond, which are significant in quantum sensing. Furthermore, the results provide deep insights into complex light-matter interactions.
关键词： single emitters,nitrogen vacancy centers in diamond,silicon nanoballs,femtosecond laser technique
更新于2025-09-23 15:19:57
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Controlling the fluorescence properties of nitrogen vacancy centers in nanodiamonds
摘要： Controlling the fluorescence properties of nitrogen vacancy centers in nanodiamonds is an important factor for their use in medical and sensor applications. However, reports providing a deep understanding of the potential factors influencing these properties are rare and focus only on a few influencing factors. The current contribution targets this issue and we report a comprehensive study of the fluorescence properties of NVs in nanodiamonds as a function of electron irradiation fluence and surface termination. Here we show that process parameters such as defect center interactions, in particular, different nitrogen defects and radiation induced lattice defects, as well as surface functionalities have a strong influence on the fluorescence intensity, fluorescence lifetime and the charge state ratio of the NV centers. By employing a time-correlated single photon counting approach we also established a method for fast macroscopic monitoring of the fluorescence properties of ND samples. We found that the fluorescence properties of NV centers may be controlled or even tuned depending upon the radiation treatment, annealing, and surface termination.
关键词： fluorescence lifetime,charge state ratio,nanodiamonds,surface termination,nitrogen vacancy centers,fluorescence properties,electron irradiation
更新于2025-09-19 17:15:36
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Apparent delocalization of the current density in metallic wires observed with diamond nitrogen-vacancy magnetometry
摘要： We report on a quantitative analysis of the magnetic field generated by a continuous current running in metallic microwires fabricated on an electrically insulating diamond substrate. A layer of nitrogen-vacancy (NV) centers engineered near the diamond surface is employed to obtain spatial maps of the vector magnetic field, by measuring Zeeman shifts through optically detected magnetic resonance spectroscopy. The in-plane magnetic field (i.e., parallel to the diamond surface) is found to be significantly weaker than predicted, while the out-of-plane field also exhibits an unexpected modulation. We show that the measured magnetic field is incompatible with Ampère’s circuital law or Gauss’s law for magnetism when we assume that the current is confined to the metal, independent of the details of the current density. This result was reproduced in several diamond samples, with a measured deviation from Ampère’s law by as much as 94(6)% (i.e., a 15σ violation). To resolve this apparent magnetic anomaly, we introduce a generalized description whereby the current is allowed to flow both above the NV sensing layer (including in the metallic wire) and below the NV layer (i.e., in the diamond). Inversion of the Biot-Savart law within this two-channel description leads to a unique solution for the two current densities that completely explains the data, is consistent with the laws of classical electrodynamics, and indicates a total NV-measured current that closely matches the electrically measured current. However, this description also leads to the surprising conclusion that in certain circumstances the majority of the current appears to flow in the diamond substrate rather than in the metallic wire, and to spread laterally in the diamond by several micrometers away from the wire. No electrical conduction was observed between nearby test wires, ruling out a conventional conductivity effect. Moreover, the apparent delocalization of the current into the diamond persists when an insulating layer is inserted between the metallic wire and the diamond or when the metallic wire is replaced by a graphene ribbon. The possibilities of a measurement error, a problem in the data analysis, or a current-induced magnetization effect are discussed, but do not seem to offer a more plausible explanation for the effect. Understanding and mitigating this apparent anomaly will be crucial for future applications of NV magnetometry to charge transport studies.
关键词： diamond magnetometry,nitrogen-vacancy centers,Biot-Savart law,Ampère's law,magnetic field imaging,current density
更新于2025-09-19 17:15:36
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Quantum reference beacon–guided superresolution optical focusing in complex media
摘要： Optical scattering is generally considered to be a nuisance of microscopy that limits imaging depth and spatial resolution. Wavefront shaping techniques enable optical imaging at unprecedented depth, but attaining superresolution within complex media remains a challenge. We used a quantum reference beacon (QRB), consisting of solid-state quantum emitters with spin-dependent fluorescence, to provide subwavelength guidestar feedback for wavefront shaping to achieve a superresolution optical focus. We implemented the QRB-guided imaging with nitrogen-vacancy centers in diamond nanocrystals, which enable optical focusing with a subdiffraction resolution below 186 nanometers (less than half the wavelength). QRB-assisted wavefront-shaping should find use in a range of applications, including deep-tissue quantum enhanced sensing and individual optical excitation of magnetically coupled spin ensembles for applications in quantum information processing.
关键词： complex media,nitrogen-vacancy centers,quantum imaging,superresolution,quantum reference beacon,optical focusing,wavefront shaping
更新于2025-09-19 17:15:36
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[IEEE 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Xiamen, China (2019.12.17-2019.12.20)] 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Ultrathin Self-feeding Metasurface with Broadband Polarization Conversion and Electromagnetic Emission
摘要： A model for controlling the two-dimensional distribution of negatively charged nitrogen-vacancy (NV?) fluorescent centers near the surface of a diamond crystal is presented, using only a microwave plasma-assisted chemical vapor deposition (CVD) method. In this approach, a CVD diamond layer is homoepitaxialy grown via microwave plasma-assisted CVD using an isotopically enriched methane (12CH4 ), hydrogen (H2 ), and nitrogen (N2 ) gas mixture on patterned diamond (0 0 1). When the surface is imaged by means of confocal microscope photoluminescence mapping, fine grooves are observed to have been generated artificially on the diamond surface. NV? centers are found to be distributed selectively into these grooves. These results demonstrate an effective means for the formation of NV? centers of selectable size and density via microwave plasma-assisted CVD, with potential application in the production of diamond quantum sensors.
关键词： doping,nitrogen-vacancy centers,homoepitaxial,groove structure,Diamond,microwave plasma-assisted chemical vapor deposition
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Multi-Qubit Registers of Individually Addressable Solid-State Defect Centers
摘要： Mesoscopic ensembles of qubits offer a platform for near-term applications in quantum technologies, as well as for studying many-body physics. Key in exploiting these systems is the ability to coherently control constituent qubits in a manner that leaves the quantum states of neighboring qubits unperturbed. Atom-like emitters in solids have emerged as a promising platform for computing, communications, and sensing. In particular, their long coherence times, coherent optical transitions, and the ability to couple to nearby long-lived nuclear spins make them excellent candidates for building medium-scale registers of coupled qubits. Here, we present progress towards producing and controlling such individually addressable ensembles. Our approach relies on the natural inhomogeneous distribution of optical transitions for solid-state color centers. This distribution allows us to excite individual centers even in tightly-grouped clusters. With this, we first demonstrate super-resolution localization and readout of individual nitrogen vacancy (NV) centers in diamond. We probe a system of three NV centers, demonstrating localization with a mean precision of 0.74 nm. While super-resolution imaging of NV centers has been achieved with other techniques, our approach uniquely allows for individual readout of single NVs in a cluster in a manner that maintains the states of nearby spins. We perform simultaneous control of two spin populations in a cluster of NVs, demonstrating preservation of coherence of one population during the optical readout of another. Lastly, we discuss recent work towards scalable creation of such clusters and techniques for producing systems of coupled spins with various defect centers.
关键词： spin-spin coupling,quantum technologies,super-resolution localization,qubits,solid-state color centers,nitrogen vacancy centers,many-body physics,atom-like emitters
更新于2025-09-16 10:30:52