Towards high-sensitivity magnetometry with nitrogen-vacancy centers in diamond using the singlet infrared absorption
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-05-07 |
| Journal | Physical Review Applied |
| Authors | Ali Tayefeh Younesi, Muhib Omar, Arne Wickenbrock, Dmitry Budker, Ronald Ulbricht |
| Institutions | Max Planck Institute for Polymer Research, Johannes Gutenberg University Mainz |
| Citations | 4 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: High-Sensitivity NV- Magnetometry via Singlet IR Absorption
Section titled âTechnical Documentation & Analysis: High-Sensitivity NV- Magnetometry via Singlet IR AbsorptionâThis document analyzes the research paper detailing high-sensitivity magnetometry using the nitrogen-vacancy (NV-) center singlet infrared (IR) absorption transition. It highlights the material requirements and limitations identified in the study and maps them directly to 6CCVDâs advanced MPCVD diamond capabilities, offering solutions for replication and performance enhancement.
Executive Summary
Section titled âExecutive Summaryâ- Core Achievement: Demonstrated room-temperature, cavity-free NV- magnetometry utilizing the singlet IR absorption transition (1E â 1A1 at 1042 nm).
- Sensitivity Benchmark: Achieved a magnetic sensitivity of 18 pT/âHz (DC to 900 Hz), the lowest reported value using singlet absorption ODMR without complex cavity enhancement.
- Performance Potential: Calculated shot-noise limit suggests potential sensitivity of 5 pT/âHz through optimization, primarily by increasing IR probe power.
- Material Limitation Identified: The study found that a hydrogen-related defect native to the CVD-grown diamond, exhibiting a zero-phonon line (ZPL) at 1358 nm, causes parasitic absorption in the 1042 nm probing range, limiting overall sensitivity.
- Material Solution Proposed: The authors suggest that substituting the CVD diamond with HPHT diamond would be a sensible choice to eliminate this defect, presenting a direct opportunity for 6CCVD to supply optimized, low-defect MPCVD SCD.
- Methodology: The technique relies on CW optical pumping (532 nm) combined with balanced photodetection of the 1042 nm probe beam across a 2.6 mm interaction length.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental results:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Achieved Magnetic Sensitivity | 18 | pT/âHz | Room temperature, cavity-free setup |
| Calculated Shot-Noise Limit | 5 | pT/âHz | Theoretical limit based on measured parameters |
| Pump Wavelength | 532 | nm | CW excitation (3A2 â 3E) |
| Probe Wavelength | 1042 | nm | Singlet IR absorption (1E â 1A1) |
| Sample Dimensions | 2.6 x 2.6 x 0.5 | mm3 | Polished on all six facets |
| Interaction Length | 2.6 | mm | Beam path through the sample |
| Substitutional Nitrogen [N] | 13 | ppm | Concentration before NV creation |
| NV Center Concentration | ~4 | ppm | Total concentration (NV- and NV0) |
| Zero-Field Splitting (ZFS) | 2.870 | GHz | 3A2 ground state |
| ODMR Linewidth (Îν) | 700 | kHz | Using MW mixing technique |
| Effective Spin Contrast (Ccw) | 1.6 | % | Maximum achieved with MW mixing |
| Bias Magnetic Field Strength | ~1 | mT | Applied along the [110] orientation |
Key Methodologies
Section titled âKey MethodologiesâThe experiment focused on optimizing absorption ODMR at room temperature without external optical cavities.
- Material Selection: A 12C-enriched, [100]-oriented CVD-grown bulk diamond sample was used, doped with 13 ppm substitutional nitrogen (N) resulting in approximately 4 ppm NV centers.
- Optical Setup: A CW 532 nm laser (pump) was combined collinearly with a CW 1042 nm tunable laser (probe) using a dichroic mirror.
- Interaction Path: The beams were focused and passed through the 2.6 mm long side of the sample to maximize the interaction length and enhance the weak singlet absorption signal.
- Spin Manipulation: A bias magnetic field (~1 mT) was applied along the [110] axis. Microwave (MW) radiation was delivered via a closed-loop wire placed on the sample.
- MW Signal Generation: A mixed MW signal system was implemented to simultaneously address all 14N hyperfine transitions for both $m_s = 0 \leftrightarrow m_s = \pm 1$ states, maximizing the effective spin contrast.
- Detection: The transmitted 1042 nm probe beam was detected using a balanced photodiode (BPD) to measure differential transmission (ÎT/T).
- Sensitivity Measurement: The MW signal was modulated at $f_{mod} = 5.6$ kHz, and the BPD output was demodulated using a lock-in amplifier (LIA) to obtain dispersive resonances, which were then converted to magnetic field sensitivity.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD provides the specialized MPCVD diamond materials and engineering services necessary to replicate this high-sensitivity magnetometry research and overcome the material limitations identified by the authors.
Applicable Materials for Enhanced Performance
Section titled âApplicable Materials for Enhanced PerformanceâThe paper explicitly notes that a CVD-native defect (ZPL at 1358 nm) interferes with the 1042 nm probe beam. 6CCVD offers tailored MPCVD solutions to mitigate this issue and maximize sensitivity:
- Low-Defect MPCVD SCD: We recommend Optical Grade Single Crystal Diamond (SCD) grown under conditions optimized for ultra-low hydrogen incorporation, effectively eliminating the 1358 nm defect that plagues standard CVD samples. This ensures maximum optical transparency at 1042 nm.
- Custom Nitrogen Doping: To achieve the high ensemble NV concentration (~4 ppm) required for high-signal magnetometry, 6CCVD offers precise, controlled nitrogen doping (up to 100s of ppm N) during the MPCVD growth process, ensuring optimal NV density for ensemble sensing.
- Isotopically Pure 12C Diamond: We supply 12C-enriched SCD/PCD to minimize 13C nuclear spin noise, crucial for achieving the narrow spin transition linewidths (700 kHz) necessary for high magnetic field resolution.
Customization Potential
Section titled âCustomization Potentialâ6CCVDâs in-house engineering and fabrication capabilities directly support the scaling and integration of this IR absorption ODMR technique:
| Research Requirement | 6CCVD Customization Capability | Value Proposition |
|---|---|---|
| Dimensions: 2.6 mm interaction length required for absorption. | Custom Dimensions & Thickness: We provide SCD plates up to 500 Âľm thick and PCD wafers up to 125 mm in diameter. We can supply bulk substrates up to 10 mm thick, allowing researchers to optimize the interaction length beyond the 2.6 mm used in this study. | Enables scaling and optimization of absorption path length. |
| Optical Quality: Polishing required on all six facets for minimal scattering. | Precision Polishing: We guarantee superior surface quality: Ra < 1 nm for SCD and Ra < 5 nm for inch-size PCD. This ensures maximum transmission efficiency for both 532 nm and 1042 nm beams over long paths. | Minimizes optical loss, pushing sensitivity toward the shot-noise limit. |
| MW Delivery: External wire used for MW application. | Integrated Metalization: 6CCVD offers custom metalization services (Au, Pt, Ti, Cu, W, Pd) for patterning integrated microwave structures (e.g., coplanar waveguides) directly onto the diamond surface. | Improves MW coupling efficiency and simplifies device integration for compact magnetometers. |
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD team specializes in defect engineering and material optimization for quantum applications. We can assist researchers in selecting the ideal material specifications (e.g., nitrogen concentration, isotopic purity, crystal orientation) required for similar NV- center IR absorption magnetometry projects, ensuring the material delivered is optimized to achieve the calculated shot-noise limit of 5 pT/âHz.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
The negatively charged nitrogen vacancy center in diamond is widely used for quantum sensing due to the sensitivity of the spin triplet in the electronic ground state to external perturbations such as strain and electromagnetic fields, which makes it an excellent probe for changes in these perturbations. The spin state can be measured through optically detected magnetic resonance, which is most commonly achieved by detecting the photoluminescence after exciting the spin-triplet transition. Recently, methods have been proposed and demonstrated that use the absorption of the infrared singlet transition at 1042 nm instead. These methods, however, require cryogenic temperatures or external cavities to enhance the absorption signal. Here, we report on our efforts to optimize the magnetometer sensitivity at room temperature and without cavities. We reach a sensitivity of <a:math xmlns:a=âhttp://www.w3.org/1998/Math/MathMLâ display=âinlineâ> <a:mn>18</a:mn> <a:mspace width=â0.2emâ/> <a:mi>pT</a:mi> <a:mo>/</a:mo> <a:msqrt> <a:mi>Hz</a:mi> </a:msqrt> </a:math> , surpassing previously reported values, and a calculated shot-noise limit of <d:math xmlns:d=âhttp://www.w3.org/1998/Math/MathMLâ display=âinlineâ> <d:mn>5</d:mn> <d:mspace width=â0.2emâ/> <d:mi>pT</d:mi> <d:mo>/</d:mo> <d:msqrt> <d:mi>Hz</d:mi> </d:msqrt> </d:math> . We also report on a defect that is native to diamond grown by chemical vapor deposition and thus absent in high-pressure high-temperature diamond, the excitation of which impacts the measured singlet absorption signal.