抗反射梯度折射率类金刚石涂层增强金刚石 NV 色心的荧光收集研究

王军旗 Jun-qi Wang, 牛刘敏 Liu-min Niu, 柴笑晗 Xiao-han Chai +4 more

M. S. J. Barson, Elmars Krausz, Neil B. Manson +1 more

Abstract The nitrogen‐vacancy (NV) center in diamond is a widely utilized system due to its useful quantum properties. Almost all research focuses on the negative charge state (NV − ) and comparatively little is understood about the neutral charge state (NV 0 ). This is surprising as the charge state often fluctuates between NV 0 and NV − during measurements. There are potentially under‐utilized technical applications that could take advantage of NV 0 , either by improving the performance of NV 0 or utilizing NV − directly. However, the fine structure of NV 0 has not been observed. Here, we rectify this lack of knowledge by performing magnetic circular dichroism measurements that quantitatively determine the fine structure of NV 0 . The observed behavior is accurately described by spin‐Hamiltonians in the ground and excited states with the ground state yielding a spin‐orbit coupling of λ = 2.24 ± 0.05 GHz and a orbital g ‐factor of 0.0186 ± 0.0005. The reasons why this fine structure has not been previously measured are discussed and strain‐broadening is concluded to be the likely reason.

Mengdi Zhang, Bai‐Yan Li, Jing Liu

In this letter, the photon-induced charge conversion dynamics of a single Nitrogen-Vacancy (NV) center in nanodiamond between two charge states, negative (NV−) and neutral (NV0), is studied by the auto-correlation function. It is observed that the ionization of NV− converts to NV0, which is regarded as the dark state of the NV−, leading to fluorescence intermittency in single NV centers. A new method, based on the auto-correlation calculation of the time-course fluorescence intensity from NV centers, was developed to quantify the transition kinetics and yielded the calculation of transition rates from NV− to NV0 (ionization) and from NV0 to NV− (recharging). Based on our experimental investigation, we found that the NV−-NV0 transition is wavelength-dependent, and more frequent transitions were observed when short-wavelength illumination was used. From the analysis of the auto-correlation curve, it is found that the transition time of NV− to NV0 (ionization) is around 0.1 μs, but the transition time of NV0 to NV− (recharging) is around 20 ms. Power-dependent measurements reveal that the ionization rate increases linearly with the laser power, while the recharging rate has a quadratic increase with the laser power. This difference suggests that the ionization in the NV center is a one-photon process, while the recharging of NV0 to NV− is a two-photon process. This work, which offers theoretical and experimental explanations of the emission property of a single NV center, is expected to help the utilization of the NV center for quantum information science, quantum communication, and quantum bioimaging.

罗文博 Luo Wenbo, 付秋明 Fu Qiuming, 王戈明 Wang Geming +9 more

李雪琴 Li Xueqin, 杨卫军 Yang Weijun, 唐艳妮 Tang Yanni +4 more

Giannis Thalassinos, Daniel J. McCloskey, Alessandro Mameli +7 more

Nitrogen vacancy (NV) centers in diamond are at the heart of many emerging quantum technologies, all of which require control over the NV charge state. Hence, methods for quantification of the relative photoluminescence intensities of the NV0 and NV− charge states, i.e., a charge state ratio, are vital. Several approaches to quantify NV charge state ratios have been reported but are either limited to bulk-like NV diamond samples or yield qualitative results. We propose an NV charge state quantification protocol based on the determination of sample- and experimental setup-specific NV0 and NV− reference spectra. The approach employs blue (400–470 nm) and green (480–570 nm) excitation to infer pure NV0 and NV− spectra, which are then used to quantify NV charge state ratios in subsequent experiments via least squares fitting. We test our dual excitation protocol (DEP) for a bulk diamond NV sample and 20 and 100 nm nanodiamond particles and compare results with those obtained via other commonly used techniques such as zero-phonon line fitting and non-negative matrix factorization. We find that DEP can be employed across different samples and experimental setups and yields consistent and quantitative results for NV charge state ratios that are in agreement with our understanding of NV photophysics. By providing robust NV charge state quantification across sample types and measurement platforms, DEP will support the development of NV-based quantum technologies.