Parallel optically detected magnetic resonance spectrometer for dozensn of single nitrogen-vacancy centers using laser-spot lattice

At a Glance

Metadata	Details
Publication Date	2020-11-06
Journal	arXiv (Cornell University)
Authors	Mingcheng Cai, Zhongzhi Guo, Fazhan Shi, Chunxing Li, Mengqi Wang
Institutions	Chinese Academy of Sciences, University of Science and Technology of China
Citations	8
Analysis	Full AI Review Included

Technical Documentation & Analysis: Parallel ODMR for NV Centers

This document analyzes the requirements and achievements detailed in the research paper, “Parallel optically detected magnetic resonance spectrometer for dozens of single nitrogen-vacancy centers using laser-spot lattice,” and aligns them with the advanced material solutions offered by 6CCVD.

Executive Summary

The research successfully demonstrates a Parallel Optically Detected Magnetic Resonance (PODMR) platform, significantly enhancing the efficiency of quantum sensing using Nitrogen-Vacancy (NV) centers in diamond.

High-Throughput Sensing: The PODMR system utilizes a 20x20 Laser-Spot Lattice (LSL) to excite and read out multiple single NV centers in parallel, achieving an 18 times speedup compared to conventional confocal ODMR.
Material Foundation: The platform relies on high-purity, [100]-oriented Single Crystal Diamond (SCD) substrates with extremely low nitrogen concentration (< 5 ppb).
Nanoscale Requirements: NV centers were created via shallow 10 keV ¹⁴N²⁺ implantation, resulting in depths critical for nanoscale sensing (5 to 11 nm).
Integrated Structures: The diamond surface featured a 25x25 array of trapezoidal nanopillars (2 µm interval) to maximize photon collection efficiency.
Spin Control: Uniform spin manipulation was achieved across the array using a large-area $\Omega$-shape coplanar microwave coil operating in the 2-5 GHz range.
Future Scaling: The authors note that efficiency is currently limited by NV center yield (80 NV centers observed vs. 400 spots), highlighting a critical need for high-quality, defect-engineered SCD substrates for future scaling to thousands of parallel sensors.

Technical Specifications

The following table extracts key quantitative parameters relevant to the diamond material and experimental performance:

Parameter	Value	Unit	Context
Diamond Material Type	Bulk SCD	N/A	Ultrapure, [100] face
Nitrogen Purity ([N])	< 5	ppb	Required for long spin coherence time
NV Center Implantation	10 keV ¹⁴N²⁺	Energy/Species	Creation of shallow NV centers
NV Center Depth	5 to 11	nm	Critical for nanoscale MR sensing
Diamond Substrate Thickness	0.5	mm	Mounted on $\Omega$-shape coplanar coil
Nanopillar Array Density	25 x 25	Array	Fabricated on diamond surface
Nanopillar Interval	2	µm	Center-to-center spacing
Laser Excitation Wavelength	532	nm	CW Green Laser
Microwave Frequency Range	2 - 5	GHz	Optimized range for $\Omega$-shape coil
Rabi Frequency (Calculated)	~ 4	MHz	Observed in parallel measurements
Alignment Precision (Z-axis)	23.2	nm	Deviation between LSL and NV array
Efficiency Improvement	18	Times	Compared to confocal technique

Key Methodologies

The core methodology relies on precise material engineering, advanced optical alignment, and high-frequency microwave control for parallel quantum state manipulation.

Substrate Selection: Ultrapure Single Crystal Diamond (SCD) with a [100] orientation and extremely low native nitrogen concentration (< 5 ppb) was selected to ensure optimal spin coherence properties.
Shallow NV Creation: NV centers were generated via low-energy 10 keV ¹⁴N²⁺ ion implantation, targeting a shallow depth profile (5-11 nm) necessary for coupling to external nanoscale samples.
Nanostructure Fabrication: Trapezoidal cylinder-shaped nanopillars were fabricated in a 25x25 array with a 2 µm interval to enhance the collection efficiency of the NV fluorescence.
Parallel Excitation (LSL): A 532 nm laser was shaped using a micro-lens array (Thorlabs MLA150-7AR-M) to create a 20x20 Laser-Spot Lattice (LSL) for simultaneous excitation of the NV array.
Microwave Delivery: A custom-fabricated $\Omega$-shape coplanar coil was used to generate a uniform, large-area microwave magnetic field (2870 MHz, 1 W input) for parallel manipulation of all NV spins.
High-Precision Alignment: A 3D auto-alignment protocol utilizing piezo scanners (200 µm range) and electric rotation stages was employed to align the LSL and the NV nanopillar array with a Z-axis deviation of < 30 nm.
Parallel Readout: Fluorescence was collected and mapped onto an EMCCD camera, allowing for simultaneous measurement of MR spectrums and Rabi oscillations across 18 NV centers.

6CCVD Solutions & Capabilities

The success of this high-throughput PODMR platform is fundamentally dependent on the quality and customization of the diamond substrate. 6CCVD is uniquely positioned to supply the next generation of materials required to scale this research from dozens to thousands of parallel sensors.

Applicable Materials

To replicate and extend this research, 6CCVD recommends the following materials, optimized for quantum sensing applications:

Material Grade	Specification	Application Focus
Optical Grade SCD	[100] or [111] orientation, [N] < 1 ppb	Ideal for shallow NV creation and high-coherence quantum sensing. Provides the lowest background fluorescence.
SCD Substrates	Custom thickness (e.g., 0.5 mm used in paper), Ra < 1 nm polishing	Optimized for subsequent nanofabrication (nanopillars) and integration with microwave circuitry.
Engineered SCD	Pre-implanted ¹⁴N or ¹⁵N	6CCVD can supply substrates pre-implanted and annealed to optimize NV yield and depth uniformity, directly addressing the yield limitation noted in the paper (80 NV centers vs. 400 spots).

Customization Potential

The complexity of the PODMR system requires highly customized diamond components that integrate seamlessly with optical and microwave hardware.

Custom Dimensions and Thickness: The paper utilized a 0.5 mm thick diamond. 6CCVD provides SCD plates in custom thicknesses ranging from 0.1 µm up to 500 µm, ensuring optimal coupling to the $\Omega$-shape coplanar coil.
Ultra-Low Surface Roughness: The fabrication of high-aspect-ratio nanopillars requires an exceptionally smooth starting surface. 6CCVD guarantees Ra < 1 nm polishing on SCD substrates, facilitating high-fidelity lithography and etching processes.
Integrated Microwave Circuitry: The $\Omega$-shape coil was fabricated externally. 6CCVD offers in-house metalization services (Au, Pt, Ti, Cu, W) for direct deposition of microwave transmission lines or coplanar waveguides onto the diamond surface, simplifying integration and improving MW field homogeneity.
Large-Area PCD for Scaling: For future high-throughput systems requiring larger arrays (e.g., 100x100), 6CCVD can provide Polycrystalline Diamond (PCD) wafers up to 125 mm in diameter, polished to Ra < 5 nm, suitable for wide-field optical applications where single-crystal coherence is not strictly required.

Engineering Support

6CCVD’s in-house PhD team specializes in defect engineering and material optimization for quantum applications. We can assist researchers in similar Nanoscale Magnetic Resonance Spectroscopy projects by:

Implantation Optimization: Consulting on ion species, energy, and dose to maximize the yield and depth uniformity of shallow NV centers (5-11 nm) required for high-throughput parallel sensing.
Material Selection: Guiding the choice between [100] and [111] orientation based on specific magnetic field alignment and NV contrast requirements.
Integration Design: Providing technical drawings and material specifications optimized for bonding, thermal management, and integration with complex optical and microwave setups.

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

View Original Abstract

We develop a parallel optically detected magnetic resonance (PODMR)\nspectrometer to address, manipulate and read out an array of single\nnitrogen-vacancy (NV) centers in diamond in parallel. In this spectrometer, we\nuse an array of micro-lens to generate 20 * 20 laser-spot lattice (LSL) on the\nobjective focal plane, and then align the LSL with an array of single NV\ncenters. The quantum states of NV centers are manipulated by a uniform\nmicrowave field from a {\Omega}-shape coplanar coil. As an experimental\ndemonstration, we observe 80 NV centers in the field of view. Among them,\nmagnetic resonance (MR) spectrums and Rabi oscillations of 18 NV centers along\nthe external magnetic field are measured in parallel. These results can be\ndirectly used to realize parallel quantum sensing and multiple times speedup\ncompared with the confocal technique. Regarding the nanoscale MR technique,\nPODMR will be crucial for high throughput single molecular MR spectrum and\nimaging.\n

Tech Support

Original Source

DOI: https://doi.org/10.1063/5.0039110