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6CCVD Research

Design of a High-Bandwidth Uniform Radiation Antenna for Wide-Field Imaging with Ensemble NV Color Centers in Diamond

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2022-06-26
JournalMicromachines
AuthorsZhiming Li, Zhonghao Li, Zhenrong Shi, Hao Zhang, Yanling Liang
InstitutionsNorth University of China
Citations4
AnalysisFull AI Review Included

Executive Summary

Section titled “Executive Summary”

This research details the design and validation of a novel hollow Ω-type microstrip antenna optimized for wide-field Optically Detected Magnetic Resonance (ODMR) imaging using ensemble Nitrogen-Vacancy (NV) color centers in diamond.

  • Antenna Type: A hollow Ω-type microstrip antenna was designed using a Rogers dielectric substrate to provide uniform, high-efficiency, and wide-bandwidth microwave radiation.
  • Uniformity Achievement: The antenna achieved 94% magnetic field uniformity (less than 6% normalized standard deviation in FWHM and contrast) across a large 4.4 x 4.4 mm2 imaging area.
  • Radiation Efficiency: The normalized ODMR contrast (radiation efficiency) was 71.8% higher than that of a traditional straight copper antenna under the same external magnetic field conditions.
  • Bandwidth Performance: The measured bandwidth reached 988 MHz, representing an 11.82 times improvement compared to the straight copper antenna (83.6 MHz).
  • Application Context: This design overcomes limitations in existing NV sensing antennas, which typically offer uniform fields only in the 1 mm2 range and have limited bandwidth (often less than 400 MHz).
  • Diamond Material: The NV centers were created in 1b-type single crystal diamond via high-energy electron irradiation (10 ± 0.5 MeV) followed by 850 °C vacuum annealing.

Technical Specifications

Section titled “Technical Specifications”
ParameterValueUnitContext
Antenna TypeHollow Ω-typeN/AMicrostrip design on Rogers substrate.
Substrate Dielectric Constant (Δr)3.66N/ARogers material.
Substrate Thickness1.524mmAntenna substrate thickness.
Antenna Central Radius (r1)4.68mmOptimized parameter for resonance.
Resonance Frequency Range2.5 to 3GHzSuitable for NV color center testing.
Measured Bandwidth (Ω-type)988MHzS11 measurement; 11.82x improvement over straight copper.
Measured S11 (Ω-type)-40.22dBAt 2.844 GHz resonance frequency.
Magnetic Field Uniformity94%Achieved in the 4.4 x 4.4 mm2 imaging area.
Radiation Efficiency Improvement71.8%Normalized contrast increase vs. straight copper antenna.
Diamond Type1b-type single crystalN/ASample dimensions 4.5 x 4.5 x 0.5 mm3.
Nitrogen Concentration100-200ppmInitial concentration in 1b diamond.
Electron Irradiation Energy10 ± 0.5MeVUsed for vacancy creation.
Electron Irradiation Dose9.8 x 1018cm-2Required dose for NV creation.
Annealing Temperature850°CVacuum annealing temperature (3 h duration).
NV Transverse Relaxation Time (T2)~1”sNV color center property.
NV Longitudinal Relaxation Time (T1)~1msNV color center property.
Magnetic Field Image Resolution1.008”mAchieved using the CMOS camera system (4 x 4 pixel averaging).

Key Methodologies

Section titled “Key Methodologies”
  1. Antenna Design and Simulation: The hollow Ω-type microstrip antenna structure was designed using HFSS software. Optimization focused on parameters (Table 1) to achieve resonance between 2.5 and 3 GHz and maximize magnetic field uniformity over the target area.
  2. Substrate Selection: A Rogers dielectric substrate (relative dielectric constant 3.66, thickness 1.524 mm) was chosen for antenna fabrication, incorporating a rectangular microstrip transmission line for impedance matching.
  3. Diamond Sample Preparation: A 1b-type single crystal diamond (4.5 x 4.5 x 0.5 mm3) with a nitrogen concentration of 100-200 ppm was selected, presenting a (100) crystal direction on the lower surface.
  4. NV Center Creation (Irradiation): The diamond was irradiated with high-energy electrons (10 ± 0.5 MeV) at a dose of 9.8 x 1018 cm-2 (approximately 3 hours) to generate vacancies.
  5. NV Center Creation (Annealing): The irradiated diamond was subjected to vacuum annealing at 850 °C for 3 hours to mobilize vacancies, allowing them to bind with nitrogen atoms and form uniformly distributed NV color centers.
  6. CW-ODMR Testing Setup: The antenna was integrated into a custom experimental system featuring a 532 nm laser, a permanent magnet (45 Gs external field), a microwave source (Keysight N5183B), and a CMOS camera for wide-field imaging.
  7. Performance Characterization: The S11 parameters and bandwidth were measured using a vector network analyzer (Keysight N5224A). Uniformity and radiation efficiency were quantified by measuring the FWHM and contrast of the ODMR signal across nine distinct points within the 4.4 x 4.4 mm2 area.

Commercial Applications

Section titled “Commercial Applications”

The development of high-bandwidth, uniform microwave radiation antennas for NV ensembles directly supports advancements in quantum sensing and metrology across several high-tech sectors:

  • Quantum Sensing and Metrology: Enabling high-precision, wide-field measurement of magnetic fields, electric fields, and temperature distributions using solid-state quantum sensors.
  • Micro-Electronics Testing: Wide-field magnetic imaging for mapping current flows, magnetic vortices, and thermal gradients in integrated circuits and micro-devices.
  • Biological Imaging: High-sensitivity magnetic resonance spectroscopy and thermometry for studying biological processes at the cellular level (e.g., single-cell magnetic imaging).
  • Materials Science: Detection of stress and strain in advanced materials, and characterization of electronic properties under pressure.
  • Quantum Device Development: Providing high-fidelity, broadband microwave control necessary for driving spin qubits in diamond, crucial for future quantum computing and communication architectures.
View Original Abstract

Radiation with high-efficiency, large-bandwidth, and uniform magnetic field radiation antennas in a large field of view are the key to achieving high-precision wide-field imaging. This paper presents a hollow Ω-type antenna design for diamond nitrogen-vacancy (NV) ensemble color center imaging. The uniformity of the antenna reaches 94% in a 4.4 × 4.4 mm2 area. Compared with a straight copper antenna, the radiation efficiency of the proposed antenna is 71.8% higher, and the bandwidth is improved by 11.82 times, demonstrating the effectiveness of the hollow Ω-type antenna.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2017 - High-sensitivity spin-based electrometry with an ensemble of nitrogen-vacancy centers in diamond [Crossref]
  2. 2011 - Electric-field sensing using single diamond spins [Crossref]
  3. 2013 - High-precision nanoscale temperature sensing using single defects in diamond [Crossref]
  4. 2010 - Temperature dependence of the nitrogen-vacancy magnetic resonance in diamond [Crossref]
  5. 2018 - Optimization of temperature sensitivity using the optically detected magnetic-resonance spectrum of a nitrogen-vacancy center ensemble [Crossref]
  6. 2013 - Stray-field imaging of magnetic vortices with a single diamond spin [Crossref]
  7. 2016 - Fabrication of all diamond scanning probes for nanoscale magnetometry [Crossref]
  8. 2018 - High-resolution magnetic resonance spectroscopy using a solid-state spin sensor [Crossref]
  9. 2014 - Efficient route to high-bandwidth nanoscale magnetometry using single spins in diamond [Crossref]

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