Cavity-Enhanced Photon Emission from a Single Germanium-Vacancy Center in a Diamond Membrane
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-06-05 |
| Journal | Physical Review Applied |
| Authors | Rasmus HĂžy Jensen, Erika Janitz, Yannik Fontana, He Yi, Olivier Gobron |
| Institutions | Technical University of Denmark, Harvard University |
| Citations | 33 |
| Analysis | Full AI Review Included |
Technical Documentation: Cavity-Enhanced GeV Emission in MPCVD Diamond
Section titled âTechnical Documentation: Cavity-Enhanced GeV Emission in MPCVD DiamondâThis document analyzes the requirements and achievements detailed in the research paper âCavity-Enhanced Photon Emission from a Single Germanium-Vacancy Center in a Diamond Membraneâ and correlates them with the advanced material capabilities offered by 6CCVD.
Executive Summary
Section titled âExecutive SummaryâThis research successfully demonstrates the integration of a single Germanium-Vacancy (GeV) center within a high-quality diamond membrane coupled to an open Fabry-PĂ©rot microcavity, achieving significant enhancement of single-photon emission.
- High Finesse Achievement: A record cavity finesse ($\mathcal{F}$) of 11,200 ± 1,700 was achieved at the Zero Phonon Line (ZPL) wavelength (603 nm), confirming the exceptional surface quality of the diamond membrane.
- Spectral Density Enhancement: The coupling resulted in a 31±1-fold increase in the peak spectral density of single-photon emission, validating the âdiamond-likeâ mode confinement approach.
- Precision Material Requirement: The experiment utilized a precisely controlled diamond membrane thickness of $t_a$ = 862±4 nm, necessary for maximizing coupling efficiency ($\beta_{exp} = 0.40 \pm 0.13%$).
- Quantum Potential: The system sets the stage for cryogenic operation, predicting a high Purcell factor ($F_P$) up to 32±16 and a reduction in excited state lifetime, crucial for efficient spin-photon interfaces.
- Material Validation: The success relies entirely on ultra-high purity, high-quality Single Crystal Diamond (SCD) suitable for thin membrane fabrication and stable Group-IV defect incorporation.
Technical Specifications
Section titled âTechnical SpecificationsâThe following table extracts key quantitative data points relevant to the material science and optical performance achieved in the study.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Defect Center | Germanium-Vacancy (GeV) | N/A | Group-IV color center |
| Diamond Membrane Thickness ($t_a$) | 862 ± 4 | nm | Optimized for electric field antinode confinement |
| Cavity Finesse ($\mathcal{F}$) | 11,200 ± 1,700 | N/A | Measured at 603 nm (ZPL) |
| ZPL Wavelength | ~603 | nm | Zero Phonon Line emission |
| Excitation Wavelength | 532 | nm | Green laser pump source |
| Spectral Density Enhancement | 31 ± 1 | Times | Increase over confocal measurement |
| Measured Coupling Efficiency ($\beta_{exp}$) | 0.40 ± 0.13 | % | Efficiency into the m=15 cavity mode |
| Predicted Purcell Factor ($F_P$) | 32 ± 16 | N/A | Projected for cryogenic operation |
| Confocal Saturation Power ($P_{sat}$) | 3.9 ± 0.3 | mW | Free-space measurement |
| Estimated Quantum Efficiency (QE) | 17 ± 3 | % | Estimated for the studied GeV center |
Key Methodologies
Section titled âKey MethodologiesâThe successful integration of the GeV center with the high-finesse cavity relied on precise material engineering and advanced fabrication techniques.
- High-Purity MPCVD Diamond Growth: The foundation of the experiment is a high-quality, low-strain Single Crystal Diamond (SCD) substrate, necessary for subsequent thin membrane fabrication and stable defect incorporation.
- Membrane Fabrication: The SCD was processed into an ultra-thin membrane with a critical thickness of 862 nm, requiring high-precision etching and polishing techniques.
- GeV Center Creation: Germanium-Vacancy centers were incorporated into the diamond (typically via ion implantation) at a specific depth (target depth 125 nm) to ensure optimal coupling to the cavity modeâs electric field antinode.
- Open Fabry-PĂ©rot Cavity Assembly: The cavity utilized a macroscopic flat mirror and a microscopic spherical mirror (Radius of Curvature $R$ â 43 ”m) machined onto a fiber tip.
- Dielectric Mirror Optimization: Both mirrors were coated with highly reflective dielectric Bragg stacks, numerically optimized for low transmission ($T_{flat} = T_{fiber} = 70$ ppm) at the ZPL wavelength (603 nm).
- Van der Waals Bonding: The diamond membrane was bonded to the flat mirror, ensuring minimal spectral diffusion and bulk-like optical properties for the embedded GeV centers.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research highlights the critical need for ultra-high quality, precisely dimensioned diamond materialsâa core offering of 6CCVD. Our capabilities directly support the replication and extension of this work to next-generation quantum devices utilizing Group-IV centers (GeV, SiV, SnV, PbV).
Applicable Materials
Section titled âApplicable MaterialsâTo replicate or extend this high-finesse cavity coupling research, Optical Grade Single Crystal Diamond (SCD) is required.
| Material Specification | 6CCVD Capability | Relevance to GeV Research |
|---|---|---|
| SCD Thickness Control | SCD plates from 0.1 ”m up to 500 ”m | We can supply membranes at the required sub-micron thickness (e.g., 862 nm) with high precision, essential for resonant coupling to âdiamond-likeâ modes. |
| Surface Quality | Polishing achieving Ra < 1 nm (SCD) | Ultra-low surface roughness is mandatory to minimize scattering losses and achieve the demonstrated cavity finesse ($\mathcal{F}$ > 10,000). |
| Purity & Defect Hosting | High-Purity MPCVD SCD | Our material is optimized for post-growth ion implantation (e.g., Ge, Sn, Pb) or in-situ doping, ensuring stable, narrow-linewidth quantum emitters. |
| Substrate Dimensions | Plates/wafers up to 125 mm (PCD) | While SCD is used here, we offer large-area PCD for scaling up related photonic components or for use as robust, large-area substrates. |
Customization Potential
Section titled âCustomization Potentialâ6CCVD provides specialized services that directly address the complex fabrication requirements of quantum photonics:
- Precision Thinning and Dicing: We offer custom laser cutting and dicing services to produce membranes of specific lateral dimensions, ensuring compatibility with microcavity mounting stages and Van der Waals bonding techniques.
- Metalization Services: For future experiments requiring electrical gating, strain tuning, or robust bonding layers (e.g., for cryogenic operation), 6CCVD offers in-house metalization using materials such as Ti, Pt, Au, Pd, W, and Cu. This is crucial for integrating electrodes or creating robust interfaces for advanced quantum registers.
- Boron Doping (BDD): For applications requiring integrated electrical control or sensing, we offer Boron-Doped Diamond (BDD) materials, which can be tailored for conductivity while maintaining high optical quality.
Engineering Support
Section titled âEngineering SupportâThe successful integration of quantum emitters into high-finesse cavities requires deep expertise in both material science and quantum optics.
6CCVDâs in-house PhD team specializes in MPCVD diamond growth and processing for quantum applications. We can assist researchers with:
- Material Selection: Optimizing SCD grade and thickness for specific ZPL wavelengths and cavity modes.
- Surface Preparation: Consulting on post-processing techniques to maintain ultra-low surface roughness necessary for high-finesse open-cavity systems.
- Defect Integration Strategy: Advising on the optimal diamond material properties for subsequent ion implantation or high-strain engineering projects involving Group-IV centers (GeV, SnV, PbV).
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
The nitrogen-vacancy center in diamond has been explored extensively as a light-matter interface for quantum information applications, however it is limited by low coherent photon emission and spectral instability. Here, we present a promising interface based on an alternate defect with superior optical properties (the germanium-vacancy) coupled to a finesse $\approx11{,}000$ fiber cavity, resulting in a $31^{+11}_{-15}$-fold increase in the spectral density of emission. This work sets the stage for cryogenic experiments, where we predict a measurable increase in the spontaneous emission rate.