Compact and Fully Integrated LED Quantum Sensor Based on NV Centers in Diamond

At a Glance

Metadata	Details
Publication Date	2024-01-24
Journal	Sensors
Authors	Jens Pogorzelski, Ludwig Horsthemke, Jonas Homrighausen, Dennis Stiegekötter, Markus Gregor
Institutions	FH Münster
Citations	28
Analysis	Full AI Review Included

Technical Documentation & Analysis: Integrated NV Center Quantum Sensor

Executive Summary

Core Achievement: Development of the smallest fully integrated NV-center quantum sensor to date, achieving a compact form factor of 0.42 cm³ (6.9 x 3.9 x 15.9 mm³).
Performance: Measured sensitivity (η) of 28.32 nT/√Hz, approaching the theoretical shot noise limit (η_SNL) of 2.87 nT/√Hz.
Cost-Effectiveness: Utilizes a low-power LED (0.1 W consumption) and cost-effective HPHT diamond microcrystals (150 µm diameter) in a stacked PCB design, making it suitable for non-laboratory, industrial applications.
Integration Level: Provides an all-electric interface by integrating the pump light source, photodiode, microwave antenna, and filtering within the sensor head, eliminating the need for external free-beam optics.
6CCVD Opportunity: The research identifies that using less contaminated diamond could reduce linewidth and increase sensitivity. 6CCVD’s high-purity MPCVD Single Crystal Diamond (SCD) is the ideal material solution to achieve the theoretical performance limits of this integrated sensor design.
Customization: 6CCVD offers custom-sized SCD and PCD plates, precise laser cutting, and integrated metalization services to optimize the sensor geometry and microwave coupling efficiency.

Technical Specifications

Parameter	Value	Unit	Context
Sensor Form Factor (Volume)	0.42	cm³	Smallest fully integrated NV-based sensor reported
Sensor Dimensions (L x W x H)	6.9 x 3.9 x 15.9	mm³	Overall size of the stacked PCB assembly
Measured Sensitivity (η)	28.32	nT/√Hz	Mean sensitivity between τ = 0.1 s and τ = 3 s
Shot Noise Limited Sensitivity (η_SNL)	2.87	nT/√Hz	Theoretical limit for CW application
Power Consumption	0.1	W	Achieved using 3.3 V, 30 mA LED current
Diamond Material Type	Microcrystal (HPHT)	N/A	Used for cost-effectiveness
Diamond Size (Approx. Diameter)	170	µm	Used in the sensor head
NV Center Concentration	2.5-3	ppm	Concentration in the microcrystals used
Zero Field Splitting (D)	2.87	GHz	ZFS center frequency at room temperature
Microwave Resonance Frequency (f_MW)	2.87	GHz	Antenna length calculated for this frequency
Maximum Internal Temperature Increase (ΔT_NVmax)	9.8	K	Relative to ambient temperature (296.2 K)
MW-PD Isolation (S₁₂)	-51	dB	Measured transmission factor over 2.4 GHz to 3.4 GHz

Key Methodologies

The sensor utilizes a highly modular, stacked construction based on three Printed Circuit Boards (PCBs) to achieve full integration:

Mechanical Structure: Three PCBs (LED-PCB, MW-PCB, PD-PCB) are stacked and aligned using fitting screws, then fixed with UV adhesive for mechanical stability.
Excitation Source: An Indium Gallium Nitride LED (525 nm dominant wavelength) is soldered onto the LED-PCB and driven by a constant current source (30 mA).
NV Material Integration: A 150 µm HPHT diamond microcrystal is fixed directly over the light-emitting chip using optical adhesive.
Microwave (MW) Delivery: The MW-PCB features an omega structure antenna, designed as a coplanar waveguide with a ground plane, optimized for resonance at the NV center ground state frequency (f_MW = 2.87 GHz).
Fluorescence Detection: A SMD photodiode is mounted on the PD-PCB. A 622 nm longpass filter foil is placed between the MW-PCB and PD-PCB to separate the NV fluorescence (dominant wavelength 637 nm) from the residual LED pump light.
Measurement Technique: Optically Detected Magnetic Resonance (ODMR) is performed using Frequency Modulation (FM) of the microwave signal, with the output fed into a Transimpedance Amplifier (TIA) and demodulated by a Lock-In Amplifier (LIA).

6CCVD Solutions & Capabilities

This research successfully demonstrates a path toward cost-effective, highly integrated quantum sensors. 6CCVD provides the advanced diamond materials and customization services necessary to transition this prototype into a high-performance, commercial-grade device.

Applicable Materials for Performance Enhancement

The paper explicitly notes that using less contaminated diamonds could reduce the line width (Δν) and increase the contrast (C_NV), thereby significantly improving sensitivity beyond the achieved 28.32 nT/√Hz.

Material Requirement	6CCVD Solution	Technical Advantage
High Sensitivity / Low Linewidth	High-Purity Single Crystal Diamond (SCD)	MPCVD growth allows for precise control of nitrogen concentration (< 1 ppb), minimizing unwanted defects and strain, which directly reduces Δν and maximizes C_NV. Ideal for reaching the theoretical η_SNL of 2.87 nT/√Hz.
Large Area / Cost-Effective Scaling	Optical Grade Polycrystalline Diamond (PCD)	Available in large wafers (up to 125mm diameter) and thicknesses up to 500 µm. Offers excellent thermal conductivity, crucial for managing heat from the LED and MW components in stationary systems.
Boron Doping (Future Work)	Boron-Doped Diamond (BDD)	Available for electrochemical or advanced quantum applications requiring conductive diamond substrates.

Customization Potential for Integrated Sensor Design

The compact, stacked PCB design requires extremely precise material dimensions and integration features. 6CCVD’s in-house capabilities directly support the replication and optimization of this sensor architecture:

Custom Dimensions and Thickness:
- 6CCVD supplies SCD and PCD plates cut to exact specifications required by the PCB stack (e.g., 6.9 mm x 3.9 mm).
- We offer SCD thicknesses from 0.1 µm up to 500 µm, allowing researchers to optimize the NV ensemble volume (currently 0.02 mm³) for maximum signal collection efficiency.
Advanced Metalization Services:
- The MW antenna is currently fabricated on a PCB. 6CCVD can integrate the antenna directly onto the diamond surface using our internal metalization capability (Au, Pt, Ti, W, Cu).
- Direct metalization of the diamond substrate minimizes signal loss, improves MW field homogeneity (Figure 2b), and further reduces the sensor’s overall volume and complexity.
Surface Quality:
- SCD plates are polished to an optical finish (Ra < 1 nm). This is essential for minimizing scattering losses in the integrated optical path (LED to diamond, diamond to filter/photodiode), maximizing the detected photon count rate (R), and improving the signal-to-noise ratio (SNR).

Engineering Support

6CCVD’s in-house PhD team can assist researchers in optimizing material selection and processing for NV Center Magnetometry projects. We provide expert consultation on:

NV Creation Optimization: Tailoring post-growth processing (e.g., high-temperature annealing) to achieve the desired NV concentration and charge state stability.
Crystal Orientation: Supplying SCD grown in specific orientations (e.g., [100] or [111]) to simplify magnetic field projection and measurement protocols.
Thermal Management: Utilizing the superior thermal properties of MPCVD diamond to mitigate the internal temperature increase (ΔT_NVmax ≈ 9.8 K observed in the paper), ensuring long-term stability and reduced ZFS drift.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Quantum magnetometry based on optically detected magnetic resonance (ODMR) of nitrogen vacancy centers in diamond nano or microcrystals is a promising technology for sensitive, integrated magnetic-field sensors. Currently, this technology is still cost-intensive and mainly found in research. Here we propose one of the smallest fully integrated quantum sensors to date based on nitrogen vacancy (NV) centers in diamond microcrystals. It is an extremely cost-effective device that integrates a pump light source, photodiode, microwave antenna, filtering and fluorescence detection. Thus, the sensor offers an all-electric interface without the need to adjust or connect optical components. A sensitivity of 28.32nT/Hz and a theoretical shot noise limited sensitivity of 2.87 nT/Hz is reached. Since only generally available parts were used, the sensor can be easily produced in a small series. The form factor of (6.9 × 3.9 × 15.9) mm3 combined with the integration level is the smallest fully integrated NV-based sensor proposed so far. With a power consumption of around 0.1W, this sensor becomes interesting for a wide range of stationary and handheld systems. This development paves the way for the wide usage of quantum magnetometers in non-laboratory environments and technical applications.

Tech Support

Original Source

DOI: https://doi.org/10.3390/s24030743

References

2021 - Integrated and Portable Magnetometer Based on Nitrogen-Vacancy Ensembles in Diamond [Crossref]
2021 - A hybrid magnetometer towards femtotesla sensitivity under ambient conditions [Crossref]
2023 - Nuclear quadrupole resonance spectroscopy with a femtotesla diamond magnetometer [Crossref]
2017 - Scanning diamond NV center probes compatible with conventional AFM technology [Crossref]
2013 - Nanoscale magnetometry with NV centers in diamond [Crossref]
2008 - Nanoscale imaging magnetometry with diamond spins under ambient conditions [Crossref]
2021 - Diamond Magnetometry and Gradiometry Towards Subpicotesla dc Field Measurement [Crossref]
2010 - Temperature Dependence of the Nitrogen-Vacancy Magnetic Resonance in Diamond [Crossref]
2013 - High-Precision Nanoscale Temperature Sensing Using Single Defects in Diamond [Crossref]