A robust fiber-based quantum thermometer coupled with nitrogen-vacancy centers
At a Glance
Section titled āAt a Glanceā| Metadata | Details |
|---|---|
| Publication Date | 2021-04-01 |
| Journal | Review of Scientific Instruments |
| Authors | Shao-Chun Zhang, Yang Dong, Bo Du, Hao-Bin Lin, Li Shen |
| Institutions | Hefei National Center for Physical Sciences at Nanoscale, University of Science and Technology of China |
| Citations | 35 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Robust Fiber-Based Quantum Thermometer
Section titled āTechnical Documentation & Analysis: Robust Fiber-Based Quantum ThermometerāExecutive Summary
Section titled āExecutive SummaryāThis research successfully demonstrates a robust, fiber-based quantum thermometer utilizing high-density Nitrogen-Vacancy (NV) ensembles in MPCVD diamond. The methodology achieves high sensitivity while effectively isolating the sensor from common environmental noise sources, paving the way for practical, microscale thermal imaging.
- Core Achievement: Demonstrated a robust quantum thermometer achieving a temperature sensitivity of 18 mK/āHz at room temperature.
- Noise Isolation: Successfully isolated temperature measurement from environmental magnetic field noise and microwave (MW) power shifts using a single lock-in measurement (FM scheme fixed at the zero-field sharp-dip frequency $f_0$).
- Material Used: High-density NV ensemble diamond grown by MPCVD, [100] oriented, with dimensions of 200 x 200 x 100 ĀµmĀ³.
- Key Mechanism: Relies on detecting the variation of the sharp-dip structure in the zero-field Optically Detected Magnetic Resonance (ODMR) spectrum.
- Application Demonstrated: Surface temperature imaging of an electronic chip (Raspberry Pi Zero W).
- Future Potential: The system is highly suitable for practical applications requiring high-precision thermal detection in ambiguous environments, such as integrated circuits and biological systems.
- Material Limitation: The current large sensor size (200 ĀµmĀ²) limits the thermal equilibrium time (ā 100 ms), necessitating smaller, high-coherence SCD membranes for improved spatial resolution and speed.
Technical Specifications
Section titled āTechnical SpecificationsāThe following hard data points were extracted from the experimental results and simulations:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Temperature Sensitivity | 18 | mK/āHz | Achieved during surface temperature imaging. |
| NV Ensemble Density ([NVā»]) | ā 0.15 | ppm | High-density ensemble used for sharp-dip ODMR. |
| Nitrogen Concentration ([N]) | ā 40 | ppm | Concentration in the MPCVD grown diamond. |
| Diamond Dimensions (L x W x T) | 200 x 200 x 100 | ĀµmĀ³ | Bulk diamond membrane attached to fiber tip. |
| Zero-Field Splitting (ZFS) | ā 2.87 | GHz | Center frequency of the ODMR sharp-dip structure. |
| ZFS Temperature Dependence ($D_{gs}$) | ā 74 | Hz/mK | Key parameter governing temperature response. |
| Optimal MW Power Range | 22 - 27 | dBm | Dynamic range offering best sensitivity (8 dBm tolerance). |
| Optimal Modulation Deviation ($f_d$) | 1.6 - 2 | MHz | Range for best temperature sensitivity. |
| Thermal Equilibrium Time | ā 100 | ms | Limitation due to large sensor size. |
| Tā Relaxation Time (Simulation) | 7.1 | ms | Used in five-level Bloch equation simulation. |
| Tā* Coherence Time (Simulation) | 0.32 | Āµs | Used in five-level Bloch equation simulation. |
| Magnetic Noise Floor | 4 | mK/āHz | Limited by lock-in input noise and detected shot noise. |
Key Methodologies
Section titled āKey MethodologiesāThe experiment relied on high-quality MPCVD diamond and a specialized frequency modulation (FM) ODMR technique to achieve robustness.
- Material Growth & Preparation: Bulk diamond with [100] surface orientation was grown via plasma assisted Chemical Vapor Deposition (MPCVD) with high nitrogen concentration ([N] ā 40 ppm) to create a high-density NV ensemble.
- Sensor Fabrication: The diamond was mechanically polished and cut into a 200 x 200 x 100 ĀµmĀ³ membrane, then attached to the tip of a multi-mode optical fiber (100 Āµm core).
- Optical Excitation: A 532 nm green laser was coupled into the fiber. Laser power was maintained below 10 mW to prevent laser-heating effects that would compromise temperature accuracy.
- Microwave (MW) Delivery: MW signal was generated, amplified (up to 27 dBm), and delivered via a five-turn copper loop antenna (0.5 mm outer diameter) wound around the fiber ceramic plug core.
- ODMR Detection Scheme: Continuous optical excitation was used alongside frequency-modulated MW driving. The resulting photoluminescence (PL) signal was processed using a lock-in amplifier (LIA).
- Noise Isolation Protocol: The MW center frequency was finely tuned to the zero-crossing point ($f_0$) of the FM ODMR spectrum. This specific frequency ensures the LIA signal is insensitive to magnetic field noise and MW power fluctuations, isolating the temperature signal.
- Temperature Imaging: The LIA signal variation was recorded while scanning the fiber tip across the surface of an electronic chip, allowing for the reconstruction of the surface temperature distribution.
6CCVD Solutions & Capabilities
Section titled ā6CCVD Solutions & CapabilitiesāThe successful replication and advancement of this quantum thermometry research depend critically on high-quality, customizable MPCVD diamond materials and precision fabrication. 6CCVD is uniquely positioned to supply the necessary components to push sensitivity toward the sub-1 mK/āHz regime and improve spatial resolution.
| Research Requirement / Challenge | 6CCVD Solution & Capability | Applicable Materials & Services |
|---|---|---|
| High-Density NV Ensemble Diamond | We provide MPCVD SCD substrates optimized for high-density NV creation. Our materials support post-processing techniques (e.g., electron irradiation, as suggested by the paper) to achieve the required high NV concentrations (0.15 ppm NVā» and higher) while maintaining spin coherence. | SCD (Single Crystal Diamond) Substrates (Up to 500 Āµm thickness, [100] or [111] orientation). |
| Miniaturization for High Resolution | The paper identifies the 200 ĀµmĀ² sensor size as a limitation on spatial resolution and thermal response time (100 ms). 6CCVD offers precision laser cutting and polishing to fabricate membranes down to micron scales, drastically improving thermal equilibrium speed. | Custom SCD Membranes (Thickness 0.1 Āµm - 500 Āµm). |
| Ultra-Smooth Surface Quality | Efficient fiber coupling and PL collection require extremely low surface roughness. 6CCVD guarantees Optical Grade Polishing with roughness Ra < 1 nm for SCD, ensuring minimal scattering losses and optimal sensor performance. | Optical Grade SCD (Ra < 1 nm). |
| On-Chip MW Antenna Integration | The experiment utilized an external copper loop antenna. 6CCVD offers in-house metalization services (Au, Pt, Pd, Ti, W, Cu) for depositing and patterning thin films directly onto the diamond surface, enabling integrated, high-efficiency on-chip antennas. | SCD with Custom Metalization (e.g., Ti/Cu or Ti/Pt/Au stacks). |
| Large-Area Polycrystalline Diamond | For scaling up similar sensing arrays or applications requiring larger sensor footprints (e.g., wide-area thermal mapping), 6CCVD can supply large-area PCD. | PCD (Polycrystalline Diamond) Wafers (Up to 125 mm diameter, Ra < 5 nm). |
| Engineering Support | Our in-house PhD team provides expert consultation on material selection, NV creation protocols (annealing, irradiation), and integration challenges for similar quantum sensing projects. | Engineering Consultation (Material selection, NV optimization). |
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
The nitrogen-vacancy center in diamond has been broadly applied in quantum sensing since it is sensitive to different physical quantities. Meanwhile, it is difficult to isolate disturbances from unwanted physical quantities in practical applications. Here, we present a fiber-based quantum thermometer by tracking the sharp-dip in the zero-field optically detected magnetic resonance spectrum in a high-density nitrogen-vacancy ensemble. Such a scheme can not only significantly isolate the magnetic field and microwave power drift but also improve the temperature sensitivity. Thanks to its simplicity and compatibility in implementation and robustness, this quantum thermometer is then applied to the surface temperature imaging of an electronic chip with a sensitivity of 18mK/Hz. It thus paves the way to high sensitive temperature measurements in ambiguous environments.
Tech Support
Section titled āTech SupportāOriginal Source
Section titled āOriginal SourceāReferences
Section titled āReferencesā- 2017 - High Sensitivity Magnetometers