Components for an Inexpensive CW-ODMR NV-Based Magnetometer

At a Glance

Metadata	Details
Publication Date	2025-08-01
Journal	Magnetism
Authors	André Bülau, Daniela Walter, Karl-Peter Fritz
Institutions	Hahn-Schickard-Gesellschaft für angewandte Forschung
Citations	1
Analysis	Full AI Review Included

Technical Documentation & Analysis: Inexpensive CW-ODMR NV-Based Magnetometer

This document analyzes the research paper “Components for an Inexpensive CW-ODMR NV-Based Magnetometer” to provide technical specifications and align the findings with 6CCVD’s advanced MPCVD diamond solutions, focusing on driving sales for high-performance quantum sensing applications.

Executive Summary

The research successfully developed a highly cost-effective (<EUR 100) continuous-wave optically detected magnetic resonance (CW-ODMR) setup utilizing nitrogen-vacancy (NV) centers in diamond for educational and COTS (Commercial Off-The-Shelf) applications.

Core Achievement: Demonstrated the fundamental principles of quantum sensing (fluorescence, ODMR, and Zeeman splitting) using inexpensive components, including green LEDs (520-528 nm) for optical excitation.
Material Limitation Highlighted: The use of High-Pressure, High-Temperature (HPHT) diamonds resulted in large Zero-Field Splitting (ZFS) values (9 MHz to 31 MHz) and broad linewidths (FWHM 13 MHz to 23 MHz), indicative of high internal strain and large NV concentration, which limits high-sensitivity magnetometry.
Microwave Excitation: A custom discrete LC resonator was designed and characterized, achieving a resonance frequency of 2.86 GHz with excellent return loss (S11 = -50.8 dB).
Optical Optimization: Inexpensive coated PET foil filters (LEE 027/787) were identified as superior to glass filters due to low autofluorescence and high blocking efficiency.
Future Miniaturization: The project aims to miniaturize the platform (π-Mk1, Ø10 mm x 40 mm volume) and improve the signal-to-noise ratio (SNR) for microdiamonds, requiring advanced integration techniques like fluorescence waveguides.
6CCVD Value Proposition: 6CCVD provides the low-strain Single Crystal Diamond (SCD) and custom fabrication services (precision cutting, metalization) necessary to transition this research from educational demonstration to high-performance, miniaturized quantum sensor prototypes.

Technical Specifications

The following table summarizes the key performance metrics and component parameters extracted from the study:

Parameter	Value	Unit	Context
Target System Cost	<100	EUR	Excluding controller/power supply
Excitation Wavelength (Dominant)	520 - 528	nm	Green LED (LED2/LED3)
Maximum Calculated Optical Power	13.2	mW	LED3 @ 50 mA
Operating Temperature Range (LED)	-40 to +100	°C	COTS component advantage
Microwave Resonance Frequency (f)	2.85976	GHz	Discrete LC Resonator
Resonator Return Loss (S11)	-50.8	dB	High quality factor
Microwave Excitation Power	+8	dBm	Maximum used power
CW-ODMR Dip Height (Max)	~300	mV	LED3 + large HPHT diamond @ 60 mA
Zero-Field Splitting (ZFS) Range	9 to 31	MHz	Dependent on HPHT diamond sample/strain
Full Width at Half Maximum (FWHM) Range	13 to 23	MHz	Dependent on HPHT diamond sample/strain
Diamond Size (CVD Slab Pieces)	~0.5 x 0.5	mm²	Laser-cut for cost reduction
Photodetector TIA Bandwidth	~200	Hz	Limited for sufficient speed

Key Methodologies

The experimental approach focused on characterizing and selecting inexpensive, off-the-shelf components suitable for demonstrating NV-based magnetometry.

LED Selection and Modification: Three green LEDs (LED1, LED2, LED3) were evaluated based on calculated optical power. LED2 was mechanically shortened (referred to as “LED2 shortened”) to reduce the distance between the LED chip and the microdiamond, maximizing excitation efficiency.
Diamond Material Testing: High-Pressure, High-Temperature (HPHT) microdiamonds (150 µm) and large HPHT slabs were used. A Chemical Vapor Deposition (CVD) slab (DNVB14) was considered but deemed too costly for the educational goal, though pieces were laser-cut to 0.5 x 0.5 mm².
Optical Filtering: Various COTS filters (gel, color glass, coated PET foil) were tested using a spectrometer. The coated PET foil filters (LEE 027/787) were selected for their high blocking efficiency of green excitation light and minimal autofluorescence.
Microwave Resonator Design: A discrete LC resonator was constructed using two SMA connectors, a 1 pF ceramic capacitor (NP0 type), and a 2 mm loop of 0.2 mm copper wire. Fine-tuning was achieved by tweaking the loop shape to match the 2.87 GHz NV resonance frequency.
CW-ODMR Measurement: Three magnetometer builds were assembled and measured. The microwave generator (ADF4351 board) was driven up to +8 dBm without an external gain block. Signals were captured using an oscilloscope or the built-in ADC of an STM32 microcontroller.
Magnetic Field Characterization: A permanent bar magnet was used to induce Zeeman splitting. A 3D Hall sensor was used as a reference to determine the applied magnetic field values, allowing for the measurement of ZFS and FWHM characteristics.

6CCVD Solutions & Capabilities

The research successfully achieved its goal of creating an inexpensive educational kit. However, the results clearly indicate that the limitations of the COTS HPHT diamond (high strain, broad FWHM) prevent the transition to high-sensitivity, research-grade magnetometry. 6CCVD specializes in providing the advanced diamond materials and custom fabrication required to overcome these limitations and scale this technology.

Applicable Materials

Research Requirement/Limitation	6CCVD Material Solution	Technical Advantage
High ZFS/FWHM (9-31 MHz): Indicates high internal strain in HPHT diamonds, limiting coherence and sensitivity.	Optical Grade Single Crystal Diamond (SCD):	Ultra-low strain, resulting in narrow FWHM (< 1 MHz typical) and minimal ZFS spread, essential for high-resolution magnetometry and advanced quantum experiments.
Need for High NV Concentration: Ensemble sensing requires high NV density for strong fluorescence signal.	High NV Concentration Polycrystalline Diamond (PCD):	Provides large-area, high-density NV ensembles (up to 125 mm wafers) for maximizing signal-to-noise ratio (SNR) in bulk sensing applications.
Future Waveguide Integration: Need for thin, low-loss diamond films for integrated optics and improved SNR.	Thin Film SCD (0.1 µm - 500 µm):	Ideal for integration into micro-optical systems and waveguides (as suggested in the paper’s future work) to enhance fluorescence collection efficiency.
CVD Slab (DNVB14) Considered: Authors noted the high cost and complexity of laser cutting small pieces (~0.5 x 0.5 mm²).	Precision Diced SCD/PCD Plates:	We provide custom dimensions and precision laser cutting services, delivering ready-to-use diamond pieces (wafers/plates up to 125 mm) down to sub-millimeter sizes with high accuracy and minimal edge strain.

Customization Potential

The paper’s future work involves miniaturization (π-Mk1 platform) and the use of integrated microwave structures and optical components. 6CCVD’s in-house capabilities directly support this advanced development:

Custom Dimensions: We supply SCD and PCD plates/wafers in custom sizes and thicknesses (SCD: 0.1 µm - 500 µm; PCD: 0.1 µm - 500 µm; Substrates up to 10 mm), perfectly matching the size constraints of the proposed Ø10 mm x 40 mm π-Mk1 platform.
Integrated Microwave Structures: The discrete LC resonator used in the paper can be replaced by integrated microwave transmission lines (e.g., coplanar waveguides) fabricated directly onto the diamond surface. 6CCVD offers in-house metalization (Au, Pt, Pd, Ti, W, Cu) for creating these high-performance structures, ensuring optimal microwave coupling and field homogeneity.
Surface Preparation: We offer ultra-smooth polishing (Ra < 1 nm for SCD, Ra < 5 nm for inch-size PCD), critical for minimizing optical scattering losses when integrating the diamond with waveguides or micro-optics.

Engineering Support

6CCVD’s in-house PhD team provides authoritative professional support to accelerate research and development:

Material Consultation: Our experts can assist with material selection for similar NV-based Magnetometry projects, helping researchers choose the optimal balance between NV concentration, strain, and cost for their specific application (e.g., high-coherence SCD for pulsed ODMR vs. high-density PCD for ensemble CW-ODMR).
Design Optimization: We offer guidance on integrating diamond into complex systems, including advice on metalization stack design for microwave coupling and surface termination for maximizing NV center stability.
Global Logistics: We ensure reliable global shipping (DDU default, DDP available) for time-sensitive research projects worldwide.

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

View Original Abstract

Quantum sensing based on NV-centers in diamonds has been demonstrated many times in multiple publications. The majority of publications use lasers in free space or lasers with fiber optics, expensive optical components such as dichroic mirrors, or beam splitters with dichroic filters and expensive detectors, such as Avalanche photodiodes or single photon detectors, overall, leading to custom and expensive setups. In order to provide an inexpensive NV-based magnetometer setup for educational use in schools, to teach the three topics, fluorescence, optically detected magnetic resonance, and Zeeman splitting, inexpensive, miniaturized, off-the-shelf components with high reliability have to be used. The cheaper such a setup, the more setups a school can afford. Hence, in this work, we investigated LEDs as light sources, considered different diamonds for our setup, tested different color filters, proposed an inexpensive microwave resonator, and used a cheap photodiode with an appropriate transimpedance amplifier as the basis for our quantum magnetometer. As a result, we identified cheap and functional components and present a setup and show that it can demonstrate the three topics mentioned at a hardware cost <EUR 100.

Tech Support

Original Source

DOI: https://doi.org/10.3390/magnetism5030018

References

2018 - Little bits of diamond: Optically detected magnetic resonance of nitrogen-vacancy centers [Crossref]
2020 - A hand-held magnetometer based on an ensemble of nitrogen-vacancy centers in diamond [Crossref]
2023 - Modular low-cost 3D printed setup for experiments with NV centers in diamond [Crossref]
2021 - Integrated and Portable Magnetometer Based on Nitrogen-Vacancy Ensembles in Diamond [Crossref]
2010 - Temperature dependence of the nitrogen-vacancy magnetic resonance in diamond [Crossref]
2023 - Temperature sensing with RF-dressed states of nitrogen-vacancy centers in diamond [Crossref]
2011 - Electric-field sensing using single diamond spins [Crossref]
2019 - Robust and Accurate Electric Field Sensing with Solid State Spin Ensembles [Crossref]