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6CCVD Research

Calibration-Free Vector Magnetometry Using Nitrogen-Vacancy Center in Diamond Integrated with Optical Vortex Beam

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2020-11-02
JournalNano Letters
AuthorsBing Chen, Xianfei Hou, Feifei Ge, Xiaohan Zhang, Yunlan Ji
InstitutionsHefei University of Technology, CAS Key Laboratory of Urban Pollutant Conversion
Citations58
AnalysisFull AI Review Included

Executive Summary

Section titled “Executive Summary”

This research details a novel, calibration-free method for high-resolution vector magnetometry utilizing Nitrogen-Vacancy (NV) centers in diamond, significantly improving efficiency over conventional techniques.

  • Calibration-Free Orientation: The orientation of individual NV centers is determined directly by scanning the diamond using an azimuthally polarized optical vortex beam. The resulting characteristic fluorescence pattern is unique to the NV center’s orientation, eliminating the need for time-consuming magnetic field calibration steps.
  • Nano-Scale Vector Magnetometry: The method achieves nano-scale spatial resolution for measuring the complete 3D magnetic field vector (magnitude and orientation).
  • Optical Vortex Beam Integration: An azimuthally polarized beam is employed for optical excitation, leveraging its inhomogeneous transverse polarization components near the focal spot to create orientation-dependent imaging patterns.
  • 3D Vector Reconstruction: The full magnetic field vector is reconstructed by combining the orientation data (from vortex scanning) with the magnitude and polar angle data (α) obtained via Optically Detected Magnetic Resonance (ODMR) from three different-oriented NV centers.
  • Efficiency Improvement: By integrating the NV center locating and calibration processes into a single optical scanning step, the overall vector magnetometry procedure is made much more efficient and suitable for real-time applications.

Technical Specifications

Section titled “Technical Specifications”
ParameterValueUnitContext
NV Center Material[111]-oriented bulk diamond-Type-IIa, single-crystal synthetic
NV Ground State Splitting (D)2.87GHzZero-field splitting (ZFS) of 3A2 state
Excitation Wavelength532nmPulsed laser source
Fluorescence Collection Range600 to 800nmDetected by SPAD
Objective Numerical Aperture (NA)1.40-Olympus oil-immersion objective lens
Polarization Extinction Ratio>100,000:1-Quality of linear polarization beam
Laser Pulse Duration (Pulsed ODMR)~400nsUsed for high-resolution ODMR spectra
Magnetic Field Magnitude (B)59.53 ± 0.26GExample measurement result (NV1)
Reconstructed Polar Angle (ΞB)8.59°Direction of the static magnetic field
Reconstructed Azimuth Angle (φB)182.56°Direction of the static magnetic field
Directional Errorless than 0.63°Error margin for the reconstructed B field direction
Microwave Delivery Gap0.1mmCopper slotline gap on coverslip

Key Methodologies

Section titled “Key Methodologies”

The experiment relies on a purpose-built confocal microscopy system integrated with specialized optics and quantum sensing techniques:

  1. Optical Setup and Vortex Beam Generation:

    • A 532 nm pulsed laser beam is linearly polarized using a Glan-Taylor polarizer to achieve an extinction ratio greater than 100,000:1.
    • This beam is passed through a Zero-Order Vortex Half-Wave Retarder (m=1) to convert it into an azimuthally polarized beam (a type of optical vortex beam).
    • The beam is focused onto the diamond sample using a high-NA (1.40) oil-immersion objective lens.

  2. Calibration-Free Orientation Determination:

    • The diamond sample is scanned in the transverse (x-y) plane using a piezoelectric transducer (PZT) stage while excited by the azimuthally polarized beam.
    • The collected fluorescence intensity pattern is recorded. Due to the inhomogeneous polarization near the focus, the pattern is highly dependent on the 3D orientation of the NV center’s excitation dipole.
    • An optimization algorithm (Nelder-Mead method) is used to fit the experimental fluorescence pattern to numerical simulations, directly yielding the polar (Ξ) and azimuth (φ) angles of the NV center axis in the laboratory frame.

  3. Magnetic Field Magnitude Measurement (ODMR):

    • Three different-oriented NV centers (NV1, NV2, NV3) are selected as magnetic sensors.
    • Pulsed ODMR is performed (using pulsed laser excitation and MW π-pulses) to obtain high-resolution spectra of the electron spin transitions (ms = 0 to ms = ±1).
    • The transition frequencies (ω1, ω2) are used to calculate the magnetic field magnitude (B) and the polar angle (α) between the magnetic field vector and the NV axis.

  4. Vector Reconstruction:

    • The polar angle (α) defines a cone of possible magnetic field orientations around each NV axis.
    • The orientations of the three NV centers are used to define three such cones.
    • The intersection of these three cones (which forms a small triangle due to experimental deviation) is analyzed using the least square method to determine the optimal solution for the absolute 3D magnetic field direction (ΞB, φB).

Commercial Applications

Section titled “Commercial Applications”

This calibration-free vector magnetometry technique is highly relevant for applications requiring fast, high-spatial-resolution magnetic field mapping:

  • Quantum Sensing and Metrology: Enabling faster deployment and operation of NV-based quantum sensors by eliminating lengthy calibration procedures.
  • Biological Magnetic Field Sensing: High-resolution imaging of magnetic structures or processes within living cells (e.g., tracking ferritin clusters or magnetic nanoparticles).
  • Condensed Matter Physics: Probing local magnetic textures, domain walls, and spin dynamics in novel materials at the nano-scale.
  • Solid-State Device Characterization: Mapping stray magnetic fields generated by microelectronic or spintronic devices with high spatial precision.
  • Real-Time Imaging: The efficiency gain allows for real-time monitoring and imaging of dynamic magnetic phenomena.
View Original Abstract

We report a new method to determine the orientation of individual nitrogen-vacancy (NV) centers in a bulk diamond and use them to realize a calibration-free vector magnetometer with nanoscale resolution. Optical vortex beam is used for optical excitation and scanning the NV center in a [111]-oriented diamond. The scanning fluorescence patterns of NV center with different orientations are completely different. Thus, the orientation information on each NV center in the lattice can be known directly without any calibration process. Further, we use three differently oriented NV centers to form a magnetometer and reconstruct the complete vector information on the magnetic field based on the optically detected magnetic resonance(ODMR) technique. Compared with previous schemes to realize vector magnetometry using an NV center, our method is much more efficient and is easily applied in other NV-based quantum sensing applications.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2013 - Optical Magnetometry

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