Point defects in insulators are considered promising candidates for quantum technologies. In keeping with this, we present an extensive optically-detected magnetic resonance (ODMR) study at room-temperature on individual TR12 centers (ZPL at 471nm), which are known in the literature since 1956. In this work we found TR12 centers to show a strong ODMR signal under optical saturation. These observed defects were created in high-purity epitaxial layers of diamond by standard irradiation and annealing processes. From the analysis of the ODMR spectra along with antibunching measurements and coherent population trapping, we proposed the energy level structure of TR12 center, consisting of ground state and excited state singlets complemented by a metastable triplet in between. Mapping the fluorescence dependence of the center on an external magnetic field and on the polarization of laser excitation, allows us to identify twelve inequivalent orientations for TR12 centers. This includes the exact orientations of the dipole transition and the triplet axes in the diamond lattice in full agreement with the results of modeling based on the proposed level structure. Furthermore, a static Jahn-Teller effect was detected through fluorescence switching between two levels at low optical excitation power, directly observable in the real-time fluorescence signal for various polarization of laser excitation. Based on these results we discuss the prospects of the TR12 center in diamond for quantum sensing and quantum information processing.
Point defects in insulators are considered promising candidates for quantum technologies. In keeping with this, we present an extensive optically-detected magnetic resonance (ODMR) study at room-temperature on individual TR12 centers (ZPL at 471nm), which are known in the literature since 1956. In this work we found TR12 centers to show a strong ODMR signal under optical saturation. These observed defects were created in high-purity epitaxial layers of diamond by standard irradiation and annealing processes. From the analysis of the ODMR spectra along with antibunching measurements and coherent population trapping, we proposed the energy level structure of TR12 center, consisting of ground state and excited state singlets complemented by a metastable triplet in between. Mapping the fluorescence dependence of the center on an external magnetic field and on the polarization of laser excitation, allows us to identify twelve inequivalent orientations for TR12 centers. This includes the exact orientations of the dipole transition and the triplet axes in the diamond lattice in full agreement with the results of modeling based on the proposed level structure. Furthermore, a static Jahn-Teller effect was detected through fluorescence switching between two levels at low optical excitation power, directly observable in the real-time fluorescence signal for various polarization of laser excitation. Based on these results we discuss the prospects of the TR12 center in diamond for quantum sensing and quantum information processing.
Abstract The TR12 color center in diamond is a self‐interstitial spin defect capable of room‐temperature atomic‐scale vector magnetometry for detecting magnetic fields of arbitrary orientation and magnitude. Measurements using the TR12 center show that the sensing dynamic range can potentially outperform that of NV centers in diamond. The powerful quantum sensing capabilities of TR12 place it as a strong alternative candidate for quantum sensing in diamond, especially in extreme magnetic fields. However, its sensitivity in existing literature is relatively low in the µT/√Hz range. This work examines the spatial distributions of TR12 centers fabricated by high‐energy carbon irradiation on an E‐grade diamond along the ion irradiation cascade. A detailed study of photoluminescence intensity, optically detected magnetic resonance contrast, and linewidth is conducted. By varying locations along ion cascades of line irradiations with different fluences, the highest sensitivity of 1.2 nT/√Hz is achieved at three orders of magnitude higher than demonstrated in existing literatures. Coherent manipulation of triplet spin states in these ensembles is evident from Rabi oscillation measurements, with decoherence times of ≈0.47 µs at the surface and ≈ 0.42 µs at the end‐of‐range. These findings significantly enhance the potential of TR12 for quantum sensing applications.
We demonstrate the use of two-photon excitation for observing the ground state optically detected magnetic resonance (ODMR) of nitrogen-vacancy centers in diamonds at room temperature. An ultrafast femtosecond laser at 1040 nm was used for excitation, while fluorescence signal read out was achieved through a combination of a PMT and a lock-in amplifier. The imaging capability of two-photon excitation fluorescence (2PEF) was utilized to map the distribution of NV centers in a bulk diamond and micro-sized diamonds. For the first time, ODMR traces of the nitrogen-vacancy center are observed with two-photon excitation, providing a promising tool for fast 3D quantum sensing and imaging.
We demonstrate the use of two-photon excitation for observing the ground-state optically detected magnetic resonance (ODMR) of nitrogen-vacancy centers in diamonds at room temperature. An ultrafast femtosecond laser at 1040 nm was used for excitation, while fluorescence signal readout was achieved through a combination of a PMT and a lock-in amplifier. The imaging capability of two-photon excitation fluorescence (2PEF) was utilized to map the relative distribution of NV centers in a bulk diamond and micro-sized diamonds. For the first time, to the best of our knowledge, ODMR traces of the nitrogen-vacancy center are observed with two-photon excitation, providing a promising tool for fast 3D quantum sensing and imaging.
The ST2 center is an optically addressable point defect in diamond that facilitates spin initialization and readout at room temperature. However, while this study presents the discovery of photostable ST2 centers first observed in a natural diamond and provides a reliable technique for artificially creating them, its chemical structure remains unknown. To assess the potential of ST2, we map out its basic optical characteristics, reveal its electronic level structure, and quantify the intrinsic transition rates. Furthermore, we investigate its response to microwaves, static magnetic fields, and the polarization of excitation laser light, revealing twelve inequivalent orientations of the ST2 center. Simultaneous exposure to microwaves and static magnetic fields also reveals an exceptionally wide acceptance angle for sensing strong magnetic fields, unlike the well-established NV center, which is sensitive only within a narrow cone aligned with its symmetry axis. This finding establishes the ST2 center as a highly promising candidate for nanoscale quantum sensing.
The nitrogen-vacancy (NV) centers in diamond have the advantages of stable triaxial structure, ultra-long electron spin coherence time and simple optical readout at room temperature. A nitrogen atom in the diamond crystal replaces a carbon atom and a vacancy is generated at the adjacent position, forming a point defect in the C3v space group structure. Its ground state and excited state are both spin triplet states. It is the key to achieving efficient preparation of optical initial state and extracting NV color center’s information in the researches of highly sensitive sensing magnetic detection, temperature detection, biological imaging, quantum computing, etc. However, there was no systematic study on relevant parameters of laser for high-concentration NV color center’s samples in previous experimental studies. Based on a high concentration diamond NV ensemble, we use pulsed optical detection magnetic resonance (ODMR) technology to systematically study the relationship among laser initial polarization time, information reading time and laser power, and the influence of laser incident polarization angle on the accuracy of sensing information. The effects of various laser parameters on the NV1 peak of ODMR on the [111] axis of the NVs of diamond are also investigated. The contrast of ODMR increases firstly with a sigmoid function and then decreases with an e-exponential function as the information reading time increases. The incident polarization angle of the laser is sinusoidal, with a period of 90°. According to the above experimental results, we finally choose the appropriate experimental parameters at 45.8 W/cm2 (300 μs of polarization, 700 ns, reading time, laser incident angle is 220°) for ODMR test. Compared with previous experimental parameters (polarization time was 50 us, read the time of 3000 ns, laser incident angle was 250°), the experimental results show that the contrast of ODMR increases from 2.1% to 4.6%, and the typical magnetic sensitivity is improved from 21.6 nT/Hz1/2 to 5.6 nT/Hz1/2. The optimization of the optical control of NVs in solid diamond is realized. The above results provide an effective support for the detection of high-sensitivity manipulation sensing based on high-concentration NV ensemble.
As promising quantum sensors, nitrogen-vacancy (N-V) centers in diamond have been widely used in frontier studies in condensed-matter physics, material science, and life sciences. In practical applications, weak laser excitation is favorable as it reduces the side effects of laser irradiation, such as phototoxicity and heating. Here we report a combined theoretical and experimental study of (near) zero-field optically detected magnetic resonance (ODMR) of N-V-center ensembles under weak 532-nm laser excitation. In this region, both the width and splitting of the ODMR spectra decrease with increasing laser power. This power dependence is reproduced with a model that accounts for the laser-induced charge neutralization of $\mathrm{N}\text{\ensuremath{-}}{V}^{\ensuremath{-}}$--N+ pairs, which alters the local electric field environment. These results are useful for the understanding and development of N-V-based quantum sensing in light-sensitive applications.