Radiofrequency response of the optically detected level anti-crossing signal in NV color centers in diamond in zero and weak magnetic fields
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2022-01-18 |
| Journal | arXiv (Cornell University) |
| Authors | А. К. Дмитриев, A. K. Vershovskiĭ |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”This research investigates the radiofrequency (RF) response of the zero-field Level Anti-Crossing (LAC) signal in Nitrogen-Vacancy (NV) centers in diamond, focusing on enhancing sensor performance in weak magnetic fields (MF).
- Core Mechanism Identified: The complex quasi-periodic structure of the RF response is definitively attributed to the Autler-Townes (AT) splitting of the anti-crossing energy levels.
- Performance Enhancement: The steepness (slope) of the central LAC resonance, critical for magnetic field sensitivity, was increased by a factor of 2.3 compared to the signal recorded without an RF field.
- Control and Tuning: The parameters of the LAC signal can be actively controlled and optimized using relatively low-frequency RF fields (4-6 MHz range).
- Flicker Noise Suppression: The use of synchronous detection via MF modulation effectively transfers the signal to a higher frequency region, significantly suppressing low-frequency laser intensity fluctuations (flicker noise).
- Application Focus: The demonstrated control and enhancement enable the creation of highly sensitive, non-microwave magnetic field sensors suitable for operation in zero and weak MF (<1 G).
- Biomedical Relevance: Eliminating the need for microwave excitation is crucial for biomedical applications, as it prevents local tissue heating during measurement.
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| Longitudinal ZFS Parameter (Dgs) | 2.87 | GHz | NV center ground state |
| Electron Spin g-factor (gs) | 2.003 | - | NV center |
| 14N Nuclear Spin g-factor (gI) | 0.403 | - | NV center |
| Longitudinal Hyperfine Splitting (A||) | -2.16 | MHz | 14N nucleus |
| Transverse Hyperfine Splitting (A⊥) | 2.7 | MHz | 14N nucleus |
| Quadrupole Splitting (P) | 4.95 | MHz | 14N nucleus |
| NV Electronic Gyromagnetic Ratio (γNV) | 2.8 | MHz/G | - |
| Laser Wavelength | 520 | nm | Pumping source |
| Laser Power | 15 | mW | Pumping power |
| Diamond Crystal Size | 0.3 x 0.3 x 0.1 | mm3 | Sample dimensions |
| NV Concentration (Average) | 3-4 · 1018 | cm-3 | Sample material |
| Transverse Splitting Std Dev (σ) | 5 | MHz | Gaussian distribution of strain field E |
| Optimal RF Frequency Range | 4 - 6 | MHz | Corresponds to LAC splitting magnitude |
| Maximum Signal Steepness Increase | 2.3 | times | Relative to LAC signal without RF |
| LAC Signal Width (HWHM, ΔB) | 2.9 ± 0.1 | G | Measured without RF field (B0=0) |
| LAC Amplitude (Normalized, Π) | 0.93 ± 0.04 | % | Normalized to total photocurrent intensity |
| MF Modulation Amplitude | 0.5 | G | Used for synchronous detection (USD-MM) |
Key Methodologies
Section titled “Key Methodologies”- Sample Preparation: Synthetic diamond (SDB 1085 60/70) was irradiated using a 5·1018 el/cm2 electron beam, followed by annealing in an argon atmosphere at 800 °C for two hours to create NV centers.
- Optical Pumping and Collection: A 520 nm diode laser (15 mW) was coupled via an optical fiber to the diamond crystal, which was coated with a reflective dielectric layer. Fluorescence was collected back through the same fiber, ensuring maximum depolarization of the pump light.
- Magnetic Field Control: External magnetic fields (B0, 0 to 10 G) were generated using a 3D system of Helmholtz rings, with the field direction set at an angle of 4π.
- RF Excitation: An RF field inductor (resonant coil, 5 ± 1 MHz range) was used to apply quasi-resonant RF fields (up to ΩRF ≈ (2π) 4.9 MHz). Experiments utilized both amplitude modulation (AM) of the RF field and modulation (MM) of the external MF.
- Signal Detection: Fluorescence was filtered (dichroic mirror, red glass filter) and measured using a silicon photodiode. The signal was fed to a synchronous detector referenced to the modulation frequency.
- Data Reconstruction: Numerical integration of the synchronously detected signals (USD-MM and USD-MM0) was performed to reconstruct the total fluorescence dependence on the magnetic field, providing a significantly higher signal-to-noise ratio than direct photocurrent recording.
- Directional Measurement: Signals were measured with the MF vector, MF modulation vector, and RF magnetic component vector maintained collinear along the <100>, <110>, and <111> axes to study angular dependence.
Commercial Applications
Section titled “Commercial Applications”- Non-Microwave Magnetic Field Sensing: Developing next-generation magnetometers that operate without microwave excitation, eliminating the need for complex MW hardware and avoiding localized heating.
- Biomedical Diagnostics and Imaging: Ideal for applications requiring magnetic sensing in biological environments (e.g., magnetocardiography, magnetoencephalography) where weak fields (<1 G) are measured and thermal effects must be strictly avoided.
- High-Sensitivity Metrology: Utilizing the 2.3X enhanced resonance steepness to create highly sensitive sensors for measuring weak magnetic fields (near zero field), improving the precision of low-field measurements.
- Quantum Sensing (Advanced): Exploiting the higher-order Autler-Townes splitting effects to create sensors optimized for maximum sensitivity at specific, non-zero magnetic field values (in the range of several Gauss), allowing for tunable sensor operation.
- Compact Frequency Standards: The high-contrast, two-frequency resonances observed in the zero-field LAC regime offer a basis for creating compact and stable frequency standards.
View Original Abstract
The response of the level anti-crossing signal to a quasi-resonant radio-frequency field, which appears in a zero magnetic field at NV color centers in diamond, is investigated. It is shown that the complex structure of this response can be explained by the Autler-Townes splitting. The possibility of controlling the parameters of the level anti-crossing signal is considered. It is shown that the slope of the central resonance recorded in this structure upon low-frequency modulation of the external magnetic field can be 2.3 times higher than the slope of the resonance recorded in the absence of an RF field. Conclusions are drawn about the nature of the level anti-crossing effect arising in zero field in NV color centers in diamond.