Efficient Extraction of Light from a Nitrogen-Vacancy Center in a Diamond Parabolic Reflector
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2018-03-30 |
| Journal | Nano Letters |
| Authors | Noel Wan, Brendan Shields, Donggyu Kim, Sara Mouradian, Benjamin Lienhard |
| Institutions | Massachusetts Institute of Technology, SUNY Polytechnic Institute |
| Citations | 89 |
| Analysis | Full AI Review Included |
6CCVD Technical Documentation: High-Efficiency Photon Extraction from NV Centers using Monolithic Diamond Parabolic Reflectors
Section titled â6CCVD Technical Documentation: High-Efficiency Photon Extraction from NV Centers using Monolithic Diamond Parabolic ReflectorsâExecutive Summary
Section titled âExecutive SummaryâThis documentation analyzes the research demonstrating highly efficient light extraction from Nitrogen-Vacancy (NV) centers in diamond using a monolithic parabolic reflector structure, achieving a major breakthrough in solid-state quantum emitter performance.
- Breakthrough Efficiency: The parabolic reflector geometry overcomes the critical limitation of Total Internal Reflection (TIR) in high-index diamond ($n=2.4$), achieving a record photon extraction efficiency ($\eta_0$) of (48 ± 5)%.
- Highest Photon Flux: The fabricated device yields the highest detected fluorescence count rate reported for a single NV center in diamond, reaching up to (5.7) $\times$ 106 counts per second ($F_{\text{sat}}$).
- Monolithic Integration: The reflector is etched directly into a bulk CVD diamond substrate using a novel gray-scale lithography and reactive-ion etching technique, ensuring high structural robustness and compatibility with near-surface NV centers (~100 nm depth).
- Broadband and Robust: The geometrical optics design is inherently broadband (600-800 nm, covering both ZPL and PSB) and robust against vertical and horizontal emitter displacements up to 200 nm.
- Scalable Quantum Platform: This technology is immediately applicable to next-generation quantum technologies, significantly improving spin readout fidelity for quantum networking, single-shot high-fidelity spin readout, and nanoscale magnetic sensing.
- Material Foundation: The success relies critically on high-purity, low-birefringence Type IIA CVD diamond substrates, a core material specialty of 6CCVD.
Technical Specifications
Section titled âTechnical SpecificationsâThe following table summarizes the key quantitative performance data and material parameters extracted from the research paper.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Photon Extraction Efficiency ($\eta_0$) | 48 ± 5 | % | Experimental Brightness (Fraction of extracted photons per spontaneous emission) |
| Simulated Collection Efficiency | > 75 | % | Across visible spectrum (NA=1.3) |
| Max Fluorescence Detection Rate ($F_{\text{sat}}$) | 5.70 $\times$ 106 | counts/s | Maximum measured rate using linear background subtraction method |
| Raw Experimental Efficiency | 12 ± 2 | % | Single-photon triggering and detection probability |
| Single Photon Purity ($g^{2}(0)$) | 0.1873(5) | - | Measured at zero-delay, $P = 1.5P_{\text{sat}}$ |
| NV Radiative Lifetime ($\tau_{\text{rad}}$) | 12.67 | ns | Extracted from correlation peak shape |
| Substrate Material | Type IIA CVD Diamond | - | High-purity, 50 ”m thickness |
| NV Depth / Parabola Focus ($f$) | ~100 | nm | Critical parameter for reflector performance |
| Implantation Energy | 85 | keV | Nitrogen ion implantation (15N) |
| Annealing Temperature | 1200 | °C | Required for NV formation |
| Reflector Height ($h$) | 5 | ”m | Fabricated device dimension |
| Final Surface Root Mean Square Error (RMSE) | 21.23 | nm | Good fit to parabolic profile (down to $\lambda / 12n$) |
Key Methodologies
Section titled âKey MethodologiesâThe highly controlled fabrication of the diamond parabolic reflector required specific steps leveraging advanced material processing techniques compatible with high-purity CVD diamond.
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Diamond Substrate Preparation:
- Used 50 ”m thick, high-purity Type IIA CVD-grown diamond.
- Implanted 15N ions at 85 keV (resulting depth ~100 nm) with a dosage of 109 15N/cm2.
- Annealed the sample at 1200 °C to form NV centers.
- Cleaned the diamond using a boiling mixture of sulphuric, nitric, and perchloric acid.
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Gray-Scale Hardmask Fabrication:
- Deposited 200 nm thick Silicon Nitride (SiN) via PECVD.
- Defined a disk in ZEP 520A electron-beam resist (EBR) using e-beam lithography (exposure at 500 ”C/cm2).
- Applied Thermal Reflow to the EBR at an optimized temperature of 215 °C for 15 minutes to produce a near-hemispherical, atomically smooth profile (AFM RMSE = 0.66 nm).
- Transferred the resist profile into the SiN hardmask using CF4 plasma etching (etch selectivity $\approx 1$).
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Diamond Reactive Ion Etching (RIE):
- Used the SiN profile as a gray-scale etch mask.
- Transferred the pattern into the diamond substrate using Inductively Coupled Oxygen Plasma RIE (0.15 Pa, bias power 500 W, RF power 240 W).
- The etch exploited the high selectivity of oxygen plasma between diamond and SiN ($\approx 28:1$).
- Etching was performed to a depth of 5 ”m, resulting in a smooth parabolic surface profile (RMSE = 21.23 nm).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD provides the specialized CVD diamond substrates and advanced engineering required to replicate, scale, and extend this breakthrough research into manufacturable quantum devices for sensing and communication.
Applicable Materials & Substrates
Section titled âApplicable Materials & SubstratesâSuccessful replication of this research hinges on the supply of ultra-high purity, low-birefringence material tailored for precise nanofabrication and quantum coherence.
- Optical Grade SCD (Single Crystal Diamond): The ideal material for NV-based quantum emitters. We supply MPCVD-grown SCD wafers, providing the low defect density and exceptional crystalline quality necessary to ensure long spin coherence times and narrow Zero-Phonon Lines (ZPLs).
- Custom Thickness Matching: The paper used 50 ”m thick diamond. 6CCVD routinely supplies SCD and PCD substrates in custom thicknesses ranging from 0.1 ”m up to 500 ”m, ensuring compatibility with specific device mounting or membrane requirements.
- Boron-Doped Substrates (BDD): For future extensions integrating electrical contacts or field effects (e.g., Stark tuning), 6CCVD offers custom BDD layers or wafers, compatible with precise device metalization.
Customization Potential & Processing Readiness
Section titled âCustomization Potential & Processing ReadinessâThe precise geometry and surface quality are critical for achieving the reported 48% extraction efficiency.
| Research Requirement | 6CCVD Capability | Value Proposition |
|---|---|---|
| High Surface Quality (Pre-etch) | Polishing up to Ra < 1 nm (SCD) | Critical for subsequent lithography steps (EBL) and minimizing scattering losses within the monolithic device structure. |
| Custom Dimensions | Plates/wafers up to 125 mm (PCD) | Enables scaling from proof-of-concept devices to production-level wafer processing. Custom laser cutting/dicing services available. |
| Integration of Metalization | Internal Capability: Au, Pt, Pd, Ti, W, Cu | Essential for integrating microwave control lines (required for spin manipulation) or electrical tuning electrodes, enabling faster development cycles. |
| Near-Surface Emitter Ready | Precision Thinning/Substrates | We can provide substrates pre-thinned to support high-energy ion implantation ($\approx 100$ nm) or direct growth of near-surface NV layers. |
Engineering Support
Section titled âEngineering SupportâThe successful NV formation involved optimized implantation and high-temperature annealing (1200 °C).
- Thermal and Chemical Stability Support: 6CCVD provides detailed technical consultation on the thermal stability of our CVD diamond materials and optimal pre- and post-processing steps (including the necessary 1200 °C annealing and harsh acid cleaning) to maximize NV yield and coherence.
- Application Expertise: Our in-house PhD team can assist with material selection and specification development for high-performance quantum projects, including nanoscale quantum sensing, quantum networking nodes, and advanced solid-state quantum computation.
- Global Supply Chain: We offer reliable Global Shipping (DDU/DDP) of sensitive, high-ppurity diamond substrates, ensuring rapid delivery to research labs worldwide.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Quantum emitters in solids are being developed for a range of quantum technologies, including quantum networks, computing, and sensing. However, a remaining challenge is the poor photon collection due to the high refractive index of most host materials. Here we overcome this limitation by introducing monolithic parabolic reflectors as an efficient geometry for broadband photon extraction from quantum emitter and experimentally demonstrate this device for the nitrogen-vacancy (NV) center in diamond. Simulations indicate a photon collection efficiency exceeding 75% across the visible spectrum and experimental devices, fabricated using a high-throughput gray scale lithography process, demonstrating a photon extraction efficiency of (41 ± 5)%. This device enables a raw experimental detection efficiency of (12 ± 1)% with fluorescence detection rates as high as (4.114 ± 0.003) à 10<sup>6</sup> counts per second (cps) from a single NV center. Enabled by our deterministic emitter localization and fabrication process, we find a high number of exceptional devices with an average count rate of (3.1 ± 0.9) à 10<sup>6</sup> cps.