Deterministic Enhancement of Coherent Photon Generation from a Nitrogen-Vacancy Center in Ultrapure Diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2017-09-07 |
| Journal | Physical Review X |
| Authors | Daniel Riedel, Immo Söllner, Brendan Shields, Sebastian Starosielec, Patrick Appel |
| Institutions | University of Basel |
| Citations | 183 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Deterministic Enhancement of Photon Generation in MPCVD Diamond
Section titled âTechnical Documentation & Analysis: Deterministic Enhancement of Photon Generation in MPCVD DiamondâThis document analyzes the research detailing the use of ultra-pure MPCVD Single-Crystal Diamond (SCD) membranes in a tunable Fabry-PĂ©rot microcavity to significantly enhance the emission rate and probability of coherent photons from Nitrogen-Vacancy (NV) centers.
Executive Summary
Section titled âExecutive SummaryâThe research validates the use of high-purity MPCVD diamond membranes for scalable quantum photonics, achieving deterministic control over NV center emission properties via resonant microcavity coupling.
- Material Validation: Ultra-pure, (100)-oriented MPCVD Single-Crystal Diamond (SCD) serves as the host material, demonstrating exceptional optical quality necessary for narrow Zero Phonon Line (ZPL) linewidths ($\leq 100$ MHz).
- Performance Enhancement: Deterministic coupling to the microcavity increased the ZPL emission probability from approximately $3% - 4%$ (bulk) to a maximum measured value of $46.7%$.
- Purcell Effect Achieved: Demonstrated a total decay rate Purcell enhancement factor ($F_P$) of 2.0, translating to a ZPL Purcell factor ($F^{ZPL}_P$) estimated between 30 and 37.7.
- Fabrication Requirements: Required the fabrication of ultra-thin SCD membranes ($t_a \leq 1$ ”m) with highly polished surfaces ($R_a \approx 0.3$ nm) achieved through plasma etching.
- Scalability for Quantum Networks: The methodology provides a clear pathway for achieving high spin-photon and spin-spin entanglement rates, overcoming key limitations posed by poor photon extraction efficiency and long decay times in bulk diamond.
- Methodology: Utilized a tunable Fabry-PĂ©rot microcavity with high finesse ($\mathcal{F} \geq 10000$) to achieve in situ spectral and spatial resonance optimization with individual NV centers.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted detailing the material properties, NV center recipe, and experimental performance metrics.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Starting Material Crystal | (100) | Orientation | High Purity MPCVD Single Crystal Diamond (SCD) |
| Membrane Thickness ($t_a$) | $\leq 1$ | ”m | Lateral dimensions typically $20 \times 20$ ”m2 |
| Membrane Surface Roughness ($R_a$) | $\approx 0.3$ | nm | Achieved via plasma etching and polishing |
| NV Implantation Species | 14N | N/A | Nitrogen dose: $2 \cdot 10^{9}$ ions/cm2 |
| Implantation Energy | 55 | keV | Targets specific NV depth for optimal coupling |
| Target NV Depth | 68 | nm | Straggle of 16 nm |
| ZPL Linewidth (Unprocessed) | $\leq 100$ | MHz | Linewidth measured at 4K prior to processing |
| Cavity Finesse ($\mathcal{F}$) | $\geq 10000$ | N/A | Achieved using Distributed Bragg Reflectors (DBRs) ($R > 99.99%$) |
| Measured Cavity Quality Factor (Q) | 58500 | N/A | Determined by ZPL linewidth and cavity dispersion |
| Total Purcell Factor ($F_P$) | 2.0 | N/A | Overall spontaneous emission rate enhancement |
| ZPL Purcell Factor ($F^{ZPL}_P$) | $\sim 30$ to 37.7 | N/A | Enhancement targeted at the coherent ZPL |
| Enhanced ZPL Emission Probability ($\eta_{ZPL}$) | $45.4%$ to $46.7%$ | % | Significant increase from the bulk value of $3-4%$ |
| Vacuum Electric Field ($E_{vac}$) in Diamond | 36.2 | kV/m | Calculated maximum field in the diamond membrane |
Key Methodologies
Section titled âKey MethodologiesâThe following sequential steps outline the material preparation and integration required to achieve deterministic photon enhancement:
- Material Sourcing: Utilizing commercially available, ultra-pure Single Crystal Diamond (SCD) grown via Chemical Vapor Deposition (CVD), specifically (100)-oriented material, to ensure minimal spectral fluctuations due to charge noise.
- NV Center Creation: Implanting Nitrogen (14N) ions at 55 keV targeting a depth of 68 nm ($2 \cdot 10^{9}$ ions/cm2) into the SCD material.
- High-Temperature Annealing: Performing multi-step, high-temperature annealing to activate the implanted defects into optically active NV centers and repair lattice damage.
- Membrane Fabrication: Employing plasma etching and microstructuring techniques to thin the SCD material into membranes with thicknesses $t_a \leq 1$ ”m and ultra-low surface roughness ($R_a \approx 0.3$ nm).
- Assembly and Transfer: Using a micro-manipulator to break out and transfer the thin diamond membranes onto a planar mirror, relying on van der Waals forces for adhesion.
- Fabry-Pérot Integration: Inserting the diamond/planar mirror assembly into a miniaturized Fabry-Pérot cavity setup, consisting of the planar mirror and a custom concave top mirror ($R = 16$ ”m), both coated with high-reflectivity DBRs ($R > 99.99%$).
- Deterministic Tuning: Utilizing three-axis nanopositioners to provide in situ spatial (lateral position $\Delta x$) and spectral (air-gap width $\Delta L$) tuning to achieve resonance between the NV ZPL and the microcavity mode.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is an expert technical supplier uniquely positioned to support the replication and advancement of this quantum photonics research due to our specialization in high-quality, custom MPCVD diamond materials and precision engineering services.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate the high-fidelity results demonstrated, researchers require diamond with extremely low native nitrogen concentration and excellent crystalline quality, mandatory for achieving narrow ZPL linewidths ($\leq 100$ MHz).
| Application Requirement | 6CCVD Material Solution | Key Benefit |
|---|---|---|
| Host Material | Optical Grade Single Crystal Diamond (SCD) | Ultra-low impurity concentration (< 1 ppb N) essential for minimal spectral diffusion and long coherence times. |
| Future Enhancements | Boron-Doped Diamond (BDD) Wafers | Allows for creating electrostatically tunable devices or integrated micro-electromechanical systems (MEMS). |
| Material Thickness | Custom Thin Film SCD | Capabilities range from 0.1 ”m up to 500 ”m, easily accommodating the critical $t_a \leq 1$ ”m membrane requirement. |
Customization Potential
Section titled âCustomization PotentialâThe research relies on extremely precise diamond processing to create thin membranes with specific dimensions and low surface roughness. 6CCVDâs engineering capabilities meet these rigorous demands:
- Precision Thinning: 6CCVD provides custom thinning and polishing down to $0.1$ ”m thickness, surpassing the $1$ ”m requirement, optimizing NV coupling depth within the membrane.
- Ultra-Low Surface Roughness: We guarantee $R_a < 1$ nm for SCD wafers, ensuring the high surface quality ($R_a \approx 0.3$ nm) necessary to minimize surface-related spectral broadening during processing.
- Custom Micro-Structuring: We offer advanced laser cutting, dicing, and customized etching processes necessary for producing high-precision, centimeter-scale wafers or small, break-out quantum membranes (such as the $20 \times 20$ ”m2 structures used in this study).
- Integrated Metalization (Future Cavities): If the research transitions to solid immersion lenses (SILs) or requires integrated electrodes for electric field control, 6CCVD provides in-house metalization capabilities, including Ti, Pt, Au, Pd, W, and Cu, deposited to custom thickness and geometry.
Engineering Support & Logistics
Section titled âEngineering Support & Logisticsâ6CCVDâs in-house PhD engineering team possesses deep expertise in the material science and physics of diamond quantum emitters.
- Consultation for Quantum Projects: Our team can assist researchers in material selection, NV implantation specifications, and post-growth processing to optimize NV properties for specific applications in spin-photon entanglement protocols and quantum memory development.
- Global Supply Chain: We ensure reliable global shipping (DDU default, DDP available upon request) of customized, high-value diamond components, maintaining material integrity through specialized packaging.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
The nitrogen-vacancy (NV) center in diamond has an optically addressable, highly coherent spin. However, a NV center even in high-quality single-crystalline material is a very poor source of single photons: Extraction out of the high-index diamond is inefficient, the emission of coherent photons represents just a few percent of the total emission, and the decay time is large. In principle, all three problems can be addressed with a resonant microcavity. In practice, it has proved difficult to implement this concept: Photonic engineering hinges on nanofabrication, yet it is notoriously difficult to process diamond without degrading the NV centers. Here, we present a microcavity scheme that uses minimally processed diamond, thereby preserving the high quality of the starting material and a tunable microcavity platform. We demonstrate a clear change in the lifetime for multiple individual NV centers on tuning both the cavity frequency and antinode position, a Purcell effect. The overall Purcell factor F P = 2.0 translates to a Purcell factor for the zero phonon line (ZPL) of F ZPL P ⌠30 and an increase in the ZPL emission probability from about 3% to 46%. By making a step change in the NVâs optical properties in a deterministic way, these results pave the way for much enhanced spin-photon and spin-spin entanglement rates.