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Applied Optics

Stimulated emission assisted time-gated detection of a solid-state spin

Bo-Wen Zhao, Xiang-Dong Chen, Enhui Wang, Y. H. Zheng, Bo Du, Li Shen, Yang Dong, Guang‐Can Guo, Fang‐Wen Sun

Published Jun 22, 2020• 3 citations
Publisher

Abstract

The nitrogen vacancy (NV) center in diamond is studied widely for magnetic field and temperature sensing at the nanoscale. Usually, the fluorescence is recorded to estimate the spin state of the NV center. Here we applied a time-gating technique to improve the contrast of the spin-dependent fluorescence. A NIR pulsed laser pumped the stimulated emission of the NV center and depleted the spontaneous emission that was excited by a green laser. We changed the relative delay between the NIR laser and the green laser. Then the spontaneous emission of the NV center in varied time windows was extracted by comparing the fluorescence intensities with and without the NIR laser. The results showed that the spin-dependent fluorescence contrast could be improved by approximately 1.8 times by applying the time gating. The background of the environment was eliminated due to temporal filtering. This work demonstrates that the stimulated emission assisted time-gating technique can be used to improve the performance of an NV center sensor in a noisy environment.

DOI
10.1364/ao.397499

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The nitrogen vacancy (NV) center in diamond is studied widely for magnetic field and temperature sensing at the nanoscale. Usually, the fluorescence is recorded to estimate the spin state of the NV center. Here we applied a time-gating technique to improve the contrast of the spin-dependent fluorescence. A NIR pulsed laser pumped the stimulated emission of the NV center and depleted the spontaneous emission that was excited by a green laser. We changed the relative delay between the NIR laser and the green laser. Then the spontaneous emission of the NV center in varied time windows was extracted by comparing the fluorescence intensities with and without the NIR laser. The results showed that the spin-dependent fluorescence contrast could be improved by approximately 1.8 times by applying the time gating. The background of the environment was eliminated due to temporal filtering. This work demonstrates that the stimulated emission assisted time-gating technique can be used to improve the performance of an NV center sensor in a noisy environment.
Nitrogen vacancy centers in diamond are among the leading solid state quantum platforms, offering exceptional spatial resolution and sensitivity for applications such as magnetic field sensing, thermometry, and bioimaging. However, in high background environments,such as those encountered in in vitro diagnostics, the performance of NV based sensors can be compromised by strong background fluorescence, particularly from substrates such as nitrocellulose. In this work, we analytically and experimentally investigate the use of pulsed laser excitation combined with time gating techniques to suppress background fluorescence and enhance the signal to noise ratio in NV based quantum sensing, with an emphasis on spin enhanced biosensing. Through experimental studies using mixed ensembles of silicon vacancy and NV centers in bulk diamond, as well as fluorescent nanodiamonds on NC substrates, we demonstrate significant improvements in NV spin resonance visibility, demonstrated by an increase of the SNR by up to 4x, and a resulting measurement time reduction by 16x. The presented technique and results here can help significantly increase the readout efficiency and speed in future applications of NV centers in high background environments, such as in IVD, where the NV centers are used as a fluorescent label for biomolecules.
The nitrogen-vacancy (NV) center in diamond has been widely used for quantum information processing, nanophotonics, and biological imaging. In this work, we experimentally studied the charge-state conversion and stimulated emission of the NV center with a near-infrared (NIR) pumping laser. The competition between these two processes resulted in a nonmonotonic dependence of the NV center’s fluorescence intensity on the NIR laser power. Fluorescence enhancement was observed with a weak NIR laser, while fluorescence depletion was observed with a high-power NIR laser. It led to the nonmonotonic change of the spatial resolution with stimulated emission depletion microscopy, which has been used for subdiffraction imaging of the NV center. Our work can help to further understand the optical mechanism and extend the applications of the NV center.
Negatively charged nitrogen-vacancy (NV) centers in diamond are promising magnetic field quantum sensors. Laser threshold magnetometry theory predicts improved NV center ensemble sensitivity via increased signal strength and magnetic field contrast. Here, we experimentally demonstrate laser threshold magnetometry. We use a macroscopic high-finesse laser cavity containing a highly NV-doped and low absorbing diamond gain medium that is pumped at 532 nm and resonantly seeded at 710 nm. This enables a 64% signal power amplification by stimulated emission. We test the magnetic field dependency of the amplification and thus demonstrate magnetic field-dependent stimulated emission from an NV center ensemble. This emission shows an ultrahigh contrast of 33% and a maximum output power in the milliwatt regime. The coherent readout of NV centers pave the way for novel cavity and laser applications of quantum defects and diamond NV magnetic field sensors with substantially improved sensitivity for the health, research, and mining sectors.
For various applications based on nitrogen-vacancy centers in diamond, high-contrast optical detection of the spin state is one of the most important techniques, and is limited by the probability of nonradiative intersystem crossing. Utilizing a time gate for fluorescence detection, this work shows that the spin-state signal's contrast is improved by partially detecting the fluorescence photons. Subsequently, information hidden in the high-level background can be revealed. This technique can help to improve the performance of quantum sensing and imaging with nitrogen-vacancy centers, especially in noisy environments.
Charged nitrogen-vacancy (NV) color centers in diamond are excellent luminescence sources for far-field fluorescence nanoscopy by stimulated emission depletion (STED). Here we show that these photostable color centers can be visualized by STED using simple continuous-wave or high repetition pulsed lasers (76 MHz) at wavelengths >700 nm for STED. Furthermore, we show that NV centers can be imaged in three dimensions (3D) inside the diamond crystal and present single-photon signatures of single color centers recorded in high density samples, demonstrating a new recording scheme for STED and related far-field nanoscopy approaches. Finally, we exemplify the potential of using nanodiamonds containing NV centers as luminescence tags in STED microscopy. Our results offer new experimental avenues in nanooptics, nanotechnology, and the life sciences.
Negatively charged nitrogen-vacancy centres in diamond are promising quantum magnetic field sensors. Laser threshold magnetometry has been a theoretical approach for the improvement of NV-centre ensemble sensitivity via increased signal strength and magnetic field contrast. In this work we experimentally demonstrate laser threshold magnetometry. We use a macroscopic high-finesse laser cavity containing a highly NV-doped and low absorbing diamond gain medium that is pumped at 532nm and resonantly seeded at 710nm. This enables amplification of the signal power by stimulated emission of 64%. We show the magnetic-field dependency of the amplification and thus, demonstrate magnetic-field dependent stimulated emission from an NV-centre ensemble. This emission shows a record contrast of 33% and a maximum output power in the mW regime. These advantages of coherent read-out of NV-centres pave the way for novel cavity and laser applications of quantum defects as well as diamond NV magnetic field sensors with significantly improved sensitivity for the health, research and mining sectors.