Integrated Magnetometry Platform with Stackable Waveguide-Assisted Detection Channels for Sensing Arrays
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-05-26 |
| Journal | Physical Review Applied |
| Authors | Michael Hoese, Michael K. Koch, Vibhav Bharadwaj, Johannes Lang, John P. Hadden |
| Institutions | The University of Tokyo, Cardiff University |
| Citations | 24 |
| Analysis | Full AI Review Included |
Integrated Diamond Magnetometry Platform: Technical Analysis and 6CCVD Solutions
Section titled âIntegrated Diamond Magnetometry Platform: Technical Analysis and 6CCVD SolutionsâThis document analyzes the research paper âAn integrated magnetometry platform with stackable waveguide-assisted detection channels for sensing arraysâ (arXiv:2012.02560v1) and outlines how 6CCVDâs advanced MPCVD diamond materials and customization capabilities can support the replication, scaling, and extension of this quantum sensing architecture.
Executive Summary
Section titled âExecutive SummaryâThe research successfully demonstrates a novel, integrated quantum sensing platform utilizing shallow-implanted Nitrogen Vacancy (NV$^{-}$) centers in diamond, optically accessed via femtosecond-laser-written waveguides.
- Core Value Proposition: Achieves efficient optical access to NV$^{-}$ ensembles located near the diamond surface (5 ”m to 25 ”m depth) using Type-II waveguides, enabling sensing without direct light exposure to the sample area.
- Material Foundation: The platform relies on high-quality, electronic grade, low-nitrogen Single Crystal Diamond (SCD) slabs (Type II, N impurities < 5 ppb).
- Performance Metrics: Demonstrated magnetic field sensitivity up to 36 ”T Hz-1/2 (confocal) and a resolution better than 6 ”T.
- Scalability: The architecture is designed for extension into two-dimensional sensing arrays, addressing large NV ensembles (105 ”m2 mode area) and yielding a theoretical sensitivity improvement factor of 41 over conventional confocal methods.
- Fabrication Method: Combines femtosecond laser writing for 3D waveguide structures with shallow nitrogen ion implantation (5 keV, 5 x 1011 cm-2 dose) and high-temperature UHV annealing (1000 °C).
- Versatility: The device is compatible with a large temperature range, from cryogenic temperatures up to 324 K, enabling both magnetic field and temperature sensing.
Technical Specifications
Section titled âTechnical SpecificationsâThe following table extracts key parameters and performance data from the research.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Diamond Material Grade | Electronic Grade, Type II | N/A | Nitrogen impurities < 5 ppb |
| Substrate Dimensions | 2 x 2 x 0.3 | mm | Slab size used for fabrication |
| Waveguide Length | 2 | mm | Matches substrate dimension |
| Waveguide Width (C-to-C) | 15 | ”m | Transverse spacing between laser tracks |
| Waveguide Depth Range | 5 to 25 | ”m | Below top diamond surface |
| Nitrogen Ion Implantation Energy | 5 | keV | Used for shallow NV creation |
| Nitrogen Ion Dose | 5 x 1011 | cm-2 | Implantation density |
| UHV Annealing Temperature | 1000 | °C | Required for NV$^{-}$ center formation |
| CW-ODMR Sensitivity (Confocal) | 36 | ”T Hz-1/2 | Benchmark measurement |
| CW-ODMR Sensitivity (Waveguide) | 62 | ”T Hz-1/2 | Detected via transmission |
| Magnetic Field Resolution | < 6 | ”T | Estimated from fit error margins |
| ODMR Linewidth (FWHM) | 7.5 | MHz | Observed in both configurations |
| Waveguide Mode Field Area (1/e2) | 105 | ”m2 | Large ensemble sensing area |
| ZFS Parameter D Gradient (dD/dT) | -40 ± 18 | kHz K-1 | Used for temperature sensing |
Key Methodologies
Section titled âKey MethodologiesâThe integrated sensor fabrication relies on precise material growth, laser processing, and defect engineering.
- Substrate Selection: Used 2 mm x 2 mm x 0.3 mm synthetic Single Crystal Diamond (SCD), Type II, electronic grade, with ultra-low nitrogen impurities (< 5 ppb).
- Waveguide Fabrication (Femtosecond Laser Writing):
- A Yb:KGW Fiber Laser (515 nm, 300 fs pulse duration, 500 kHz repetition rate, 100 mW power) was focused using a high-NA objective (1.25 NA).
- Type-II waveguides were created by writing two nearby lines of reduced refractive index, utilizing the stressed region between them as the waveguide core.
- NV$^{-}$ Center Creation (Shallow Implantation):
- Nitrogen ions (N15+) were implanted into the front facet of the diamond platform.
- Implantation parameters were 5 keV energy and a dose of $5 \times 10^{11}$ cm-2, targeting NV creation a few nanometers below the surface.
- Thermal Processing:
- Substrates were annealed in Ultra-High Vacuum (UHV) at 1000 °C for 3 hours to mobilize vacancies and form stable NV$^{-}$ centers.
- Surface Cleaning:
- Aggressive acid boiling (1:1:1 mixture of sulphuric, perchloric, and nitric acid) was performed between processing steps to remove graphitic and organic residues, ensuring a clean surface for sensing.
- Optical Detection: CW-ODMR measurements were performed using 532 nm excitation and collecting the NV fluorescence (630 nm to 740 nm) through the waveguide mode.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to supply the foundational diamond material required for this advanced integrated quantum sensing research and to facilitate its scaling into commercial arrays.
Applicable Materials
Section titled âApplicable MaterialsâThe success of this platform hinges on the quality and purity of the diamond host.
| Research Requirement | 6CCVD Material Solution | Technical Justification |
|---|---|---|
| Ultra-High Purity Substrate | SCD (Electronic Grade, Low N) | Provides the necessary low background nitrogen (< 5 ppb) essential for controlled NV$^{-}$ creation via implantation, minimizing background noise. |
| High-Quality SCD Plates | SCD Plates (0.1 ”m to 500 ”m) | Ensures the high crystal quality and low birefringence required for efficient femtosecond laser writing of Type-II waveguides and low-loss photon routing. |
| Large-Area Arrays | PCD Wafers (Up to 125 mm) | For scaling the architecture into large 2D sensing arrays, 6CCVD offers large-area Polycrystalline Diamond (PCD) substrates, or thick SCD substrates (up to 10 mm) for robust platforms. |
Customization Potential
Section titled âCustomization PotentialâThe research utilized specific dimensions (2 mm x 2 mm x 0.3 mm) and required precise surface preparation for shallow implantation. 6CCVD offers comprehensive customization services to optimize the substrate for integration.
- Custom Dimensions and Thickness: 6CCVD can supply SCD plates in the exact thickness (0.3 mm) and custom lateral dimensions required for specific experimental setups or for scaling up to larger arrays (e.g., 10 mm thick substrates).
- Ultra-Low Roughness Polishing: Shallow implantation and subsequent surface sensing require atomically smooth surfaces. 6CCVD guarantees Ra < 1 nm polishing for SCD, ensuring optimal surface quality for both implantation and subsequent biological/material sensing applications.
- Metalization Services: Although the paper used an external wire for MW delivery, future integrated designs may require on-chip microwave structures. 6CCVD offers internal metalization capabilities (Au, Pt, Pd, Ti, W, Cu) for depositing coplanar waveguides (CPWs) directly onto the diamond surface, streamlining the integration of the MW field delivery system.
- Laser Cutting and Shaping: 6CCVD provides precision laser cutting services to achieve complex geometries or specific facet orientations necessary for coupling light into the laser-written waveguides.
Engineering Support
Section titled âEngineering SupportâThe integration of laser writing, ion implantation, and ODMR spectroscopy is highly complex. 6CCVDâs in-house PhD team specializes in optimizing diamond substrates for quantum applications.
- Material Optimization for Implantation: Our experts can consult on optimizing SCD crystal orientation and surface termination to maximize the yield and coherence time of shallow-implanted NV$^{-}$ centers for similar Integrated Quantum Magnetometry projects.
- Scaling and Array Design: We provide technical consultation on selecting the appropriate diamond type (SCD vs. PCD) and dimensions for scaling the demonstrated architecture into large, high-density 2D sensing arrays.
- Global Logistics: 6CCVD ensures reliable global shipping (DDU default, DDP available) for sensitive, high-value diamond substrates, supporting international research collaborations.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
The negatively charged nitrogen vacancy (N-Vâ) center in diamond has shown great success in nanoscale, high-sensitivity magnetometry. Efficient fluorescence detection is crucial for improving the sensitivity. Furthermore, integrated devices enable practicable sensors. Here, we present an integrated architecture which allows us to create N-Vâ centers a few nanometers below the diamond surface, and at the same time covering the entire mode field of femtosecond-laser-written type-II waveguides. We experimentally verify the coupling efficiency, showcase the detection of magnetic resonance signals through the waveguides and perform proof-of-principle experiments in magnetic field and temperature sensing. The sensing task can be operated via the waveguide without direct light illumination through the sample, which is important for magnetometry in biological systems that are sensitive to light. In the future, our approach will enable the development of two-dimensional sensing arrays facilitating spatially and temporally correlated magnetometry.