Efficient Photon Collection from a Nitrogen Vacancy Center in a Circular Bullseye Grating
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2015-02-25 |
| Journal | Nano Letters |
| Authors | Luozhou Li, Edward H. Chen, Jiabao Zheng, Sara Mouradian, Florian Dolde |
| Institutions | Element Six (United States), Massachusetts Institute of Technology |
| Citations | 206 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: High-Efficiency NV Center Photon Collection
Section titled âTechnical Documentation & Analysis: High-Efficiency NV Center Photon CollectionâExecutive Summary
Section titled âExecutive SummaryâThis paper presents a significant advancement in quantum material engineering, demonstrating a nanophotonic circular âbullseyeâ grating etched into MPCVD diamond to efficiently collect Nitrogen-Vacancy (NV) center fluorescence. 6CCVD recognizes this work as critical for scaling quantum technologies.
- World-Record Collection Rate: Achieved the highest reported single NV photon collection rate: $(3.0 \pm 0.1) \times 10^{6}$ counts per second (cts/s), representing a 10-fold increase over comparable NVs in bulk diamond.
- Millisecond Coherence Preservation: The nanofabrication process successfully maintained exceptional spin coherence, measuring $T_{2,CPMG} = 1.7 \pm 0.1$ ms, comparable to the parent bulk material.
- Material Dependence: The success is founded upon ultra-high purity, intrinsic Single Crystal Diamond (SCD) with low nitrogen concentrations (<100 ppb).
- Nanofabrication Requirement: The device required precise thinning of $\sim 5$ ”m MPCVD diamond down to a $\sim 300$ nm membrane using Reactive Ion Etching (RIE).
- Scalable Architecture: The planar design is suitable for on-chip integration with detectors and optical components, directly supporting the development of scalable multi-qubit quantum network nodes.
- Core Application: This high-efficiency coupling method is essential for high-performance quantum devices, including room temperature single-photon sources and single-shot spin readout.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Single Photon Count Rate ($C_{\infty}$) | $3.0 \pm 0.1$ | $10^{6}$ cts/s | World-leading photon collection rate from a single NV center. |
| Spin Coherence Time ($T_{2,CPMG}$) | $1.7 \pm 0.1$ | ms | Longest coherence achieved in nanofabricated diamond structures under ambient conditions. |
| Hahn Echo Coherence Time ($T_{2,Hahn}$) | $311 \pm 23$ | ”s | Measured using a Hahn Echo pulse sequence. |
| Spin-Lattice Relaxation ($T_{1}$) | $5.9 \pm 0.5$ | ms | Intrinsic material quality measurement. |
| Second-Order Autocorrelation ($g^{(2)}(0)$) | $0.320 \pm 0.005$ | N/A | Confirms operation as a single photon emitter. |
| Saturation Excitation Power ($P_{sat}$) | $2.5$ | mW | Laser power required to reach maximum count rate. |
| Diamond Membrane Thickness | $\sim 300$ | nm | Final RIE etched thickness for optimal grating performance. |
| Initial Diamond Thickness | $\sim 5$ | ”m | Thickness of the parent MPCVD SCD wafer. |
| Nitrogen Concentration | <100 | ppb | Required intrinsic level to achieve high $T_{2}$ coherence times. |
| Bullseye Grating Period ($a$) | 330 | nm | Optimized for the second-order Bragg condition at $\sim 680$ nm. |
| Air Gap (Grating) | 99 | nm | Spacing between circular grating lines. |
| Calculated Collection Efficiency (NA=1.5) | >90 | % | Optimized for narrow-band NV zero-phonon line (637 nm) applications. |
Key Methodologies
Section titled âKey MethodologiesâThe successful implementation of the nanophotonic bullseye grating relied on highly controlled MPCVD growth and subsequent precision nanofabrication techniques.
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High-Purity Material Growth:
- Diamond was grown using Microwave Plasma Assisted Chemical Vapor Deposition (MPCVD).
- Material specifications included intrinsic NV centers at a density of $\sim 1/\mu$m3 and ultra-low nitrogen concentration (<100 ppb).
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Membrane Fabrication:
- The MPCVD grown diamond structure (initial thickness $\sim 5$ ”m) was thinned via Reactive Ion Etching (RIE) to create a $\sim 300$ nm membrane.
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Grating Patterning:
- Grating patterns were defined using pre-patterned single-crystal silicon membranes, which served as robust etch hard masks.
- The bullseye structure consisted of concentric slits fully etched into the membrane, designed to satisfy the Bragg condition ($a = 330$ nm, air gap 99 nm).
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Device Integration:
- Patterned membranes were transferred onto a glass coverslip.
- The setup included a pre-patterned microwave strip line adjacent to the bullseye grating array, enabling simultaneous optical and Optically-Detected Magnetic Resonance (ODMR) characterization.
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Characterization:
- Optically-Detected Magnetic Resonance (ODMR) was used to confirm spin transitions.
- Hahn Echo and Carr-Purcell-Meiboom-Gill (CPMG) sequences were employed to measure $T_{2}$ coherence times, validating that the nanofabrication process did not degrade spin properties.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to supply the advanced MPCVD diamond materials and precision engineering services necessary to replicate, optimize, and scale the nanophotonic devices described in this research.
Applicable Materials
Section titled âApplicable MaterialsâThe foundation of this research is ultra-high purity SCD. 6CCVD provides materials precisely matched to the requirements of millisecond coherence NV centers.
| Research Requirement | 6CCVD Material Solution | Why 6CCVD is the Expert Choice |
|---|---|---|
| Ultra-High Purity SCD | Optical Grade SCD Wafers | Guarantees intrinsic N content (<100 ppb) and low defect density necessary for $T_{2}$ coherence times approaching the $1.7$ ms achieved in the study. |
| Membrane Fabrication Prep | SCD Substrates for RIE Thinning | We offer initial diamond substrate thicknesses suitable for aggressive etching (e.g., $10$ ”m, $50$ ”m, $100$ ”m) tailored for eventual $300$ nm membrane formation. |
Customization Potential
Section titled âCustomization PotentialâThe complexity of creating high-efficiency quantum devices demands capabilities that go beyond simple material supply. 6CCVD offers end-to-end engineering support for nanophotonic integration.
- Custom Dimensions and Etching Preparation: The paper utilized thin, specific membrane geometries. 6CCVD provides SCD wafers up to $125$mm in diameter and controls thickness from $0.1$ ”m to $500$ ”m, crucial for engineers optimizing membrane thickness for specific collection wavelengths ($\lambda$).
- Precision Polishing for Lithography: Achieving the $330$ nm grating feature size requires an extremely flat, high-quality surface. 6CCVD provides industry-leading SCD polishing (Ra < 1 nm), ensuring optimal surface preparation for high-resolution silicon hard mask transfer and RIE uniformity across large areas.
- Advanced Device Integration Support: The integration utilized a pre-patterned microwave strip line (MW). 6CCVD offers in-house custom metalization capabilities (Au, Pt, Pd, Ti, W, Cu), allowing researchers to quickly iterate on complex device architectures that require simultaneous optical excitation, microwave control, and electrical readout.
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD team can assist with material selection and optimization for similar NV-based Quantum Sensing and Photonic Integration projects. Our expertise ensures that the supplied material properties (e.g., nitrogen control, crystal orientation, surface termination) are perfectly suited to maximize the collection efficiency and spin coherence demonstrated in this bullseye grating research.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Efficient collection of the broadband fluorescence from the diamond nitrogen vacancy (NV) center is essential for a range of applications in sensing, on-demand single photon generation, and quantum information processing. Here, we introduce a circular âbullseyeâ diamond grating which enables a collected photon rate of (2.7 ± 0.09) Ă 10(6) counts per second from a single NV with a spin coherence time of 1.7 ± 0.1 ms. Back-focal-plane studies indicate efficient redistribution of the NV photoluminescence into low-NA modes by the bullseye grating.