Tunable cavity coupling of the zero phonon line of a nitrogen-vacancy defect in diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2015-12-16 |
| Journal | New Journal of Physics |
| Authors | S Johnson, P. R. Dolan, T. Grange, A. A. P. Trichet, G Hornecker |
| Citations | 70 |
| Analysis | Full AI Review Included |
Technical Analysis and Commercial Solutions: Tunable Cavity Coupling of NV- Defects
Section titled âTechnical Analysis and Commercial Solutions: Tunable Cavity Coupling of NV- DefectsâExecutive Summary
Section titled âExecutive SummaryâThis research demonstrates a critical step toward scalable quantum computing by achieving tunable, enhanced zero-phonon line (ZPL) emission from single Nitrogen-Vacancy (NV-) centers in nanodiamonds coupled to an open microcavity.
- Core Achievement: Controlled enhancement of the NV- ZPL using an open, plano-concave microcavity operated at cryogenic temperature (77K).
- Purcell Effect Demonstration: Achieved a factor of ~10 enhancement for individual ZPL transitions, corresponding to a 40% increase in the overall NV- emission rate (lifetime reduced from 30.8 ns to 22.1 ns).
- Methodology: Employed Focused Ion Beam (FIB) milling to create concave mirror features, combined with high-reflectivity dielectric Bragg stacks (R >99.99%). In-situ tuning was accomplished via piezoelectric actuators.
- Key Limitation Identified: Performance is currently limited by the low crystalline quality and high inhomogeneous broadening of the NV- centers hosted in High-Pressure High-Temperature (HPHT) nanodiamonds (Debye Waller Factor = 0.044).
- Future Potential: Projections suggest that substituting low-quality diamond with high-quality, MPCVD Single Crystal Diamond (SCD) could yield emission rate enhancements exceeding 103, crucial for building highly efficient spin-photon interfaces.
- 6CCVD Value Proposition: 6CCVDâs ultra-high purity, custom Single Crystal Diamond (SCD) materials are the necessary enabling platform for achieving the next generation of projected performance metrics in solid-state quantum optics.
Technical Specifications
Section titled âTechnical SpecificationsâData extracted from the experimental results and setup parameters described in the paper.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Operating Temperature | 77 | K | Cryogenic environment (Liquid Nitrogen Bath) |
| NV- ZPL Wavelength | 637 | nm | Zero Phonon Line transition wavelength |
| Excitation Wavelength | 532 | nm | CW and Pulsed excitation source |
| Nanodiamond Diameter | 100 | nm | Average size of HPHT nanodiamond host |
| Out-of-Cavity Lifetime (Ï) | 30.8 ± 0.6 | ns | Baseline NV- emission lifetime |
| In-Cavity Lifetime (Ï) | 22.1 ± 0.4 | ns | Lifetime at optimal cavity tuning (q=4) |
| Emission Rate Enhancement | 39.5 ± 0.7 | % | Overall fractional increase in emission rate (Ftot=1.395) |
| ZPL Transition Enhancement | ~10 | N/A | Enhancement factor for individual ZPL transitions |
| Concave Mirror Reflectivity | >99.99 | % | Achieved using 20 pairs of SiO2/Ta2O5 Bragg pairs |
| Planar Mirror Reflectivity | 99.7 | % | Achieved using alternating λ/4n layers of SiO2/TiO2 |
| Concave Mirror Radius (R) | 7.6 | ”m | Radius of curvature of the FIB-milled features |
| Shortest Cavity Length (L) | 1.11 | ”m | Corresponds to the longitudinal mode index q=4 |
| NV- Defect Orientation | 49 | ° | Relative to the optical axis of the cavity |
| ZPL Linewidth (FWHM) | 0.4 | nm | Due primarily to inhomogeneous broadening |
Key Methodologies
Section titled âKey MethodologiesâThe experiment utilized high-precision fabrication and low-temperature control to realize the tunable spin-photon interface.
- Nanodiamond Preparation:
- NV- defects are embedded within High-Pressure High-Temperature (HPHT) synthesized nanodiamonds (100 nm diameter).
- Nanodiamond solution is spin-cast onto the planar dielectric mirror substrate.
- Cavity Fabrication:
- Concave Mirror: Produced by Focused Ion Beam (FIB) milling of fused silica substrates. Coated with 20 pairs of SiO2/Ta2O5 to achieve R >99.99%.
- Planar Mirror: Coated in-house with alternating λ/4n layers of SiO2/TiO2 to achieve R = 99.7%. Critically, the mirror is terminated with a low index layer to position an electric field anti-node at the surface for emitter coupling.
- In-Situ Tuning and Alignment:
- The microcavity assembly uses piezoelectric actuators to provide full control of the cavity length and relative position of the planar and concave mirrors.
- Cavity length (L) is adjusted to tune the TEM00 mode resonance wavelength (λcav) through the NV- ZPL at 637 nm.
- Measurement Environment:
- Optical measurements (fluorescence, lifetime, photon autocorrelation g(2)(0)) were performed at 77K inside a liquid nitrogen bath cryostat using a custom beam-scanning confocal microscope.
- Modeling and Analysis:
- Finite Difference Time Domain (FDTD) simulations were used to model the dielectric environment and predict the Purcell enhancement factors (FPZPL and FPPSB), confirming cavity parameters and mode structure.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD provides the advanced diamond substrates and fabrication services necessary to move this research from proof-of-concept (using sub-optimal HPHT nanodiamonds) to commercially viable, scalable quantum devices by providing the highest quality material platform.
The primary requirement for achieving the theoretical enhancement limit (Ftot > 103) is transitioning from HPHT nanodiamonds to high-purity, low-strain MPCVD Single Crystal Diamond (SCD).
| Research Requirement / Limitation | 6CCVD Material Recommendation | 6CCVD Capability Advantage |
|---|---|---|
| Limitation: Performance bottlenecked by spectral instability and inhomogeneous broadening (0.4 nm linewidth) of NV- centers in HPHT nanodiamonds. | Optical Grade SCD (Single Crystal Diamond) | Our MPCVD SCD offers ultra-low nitrogen incorporation and minimal strain, achieving ZPL linewidths down to < 0.1 nm, directly enabling the high Qeff necessary for major (>103) Purcell enhancements. |
| Limitation: Emitter alignment difficulty; nanodiamonds were spin-cast resulting in non-optimal spatial overlap (Ο”) and orientation (Ξ). | Custom SCD Plates for Targeted Implantation | We supply SCD substrates up to 500 ”m thickness, ideally polished (Ra < 1 nm) for clean surface termination and ready for controlled ion implantation (not spin-casting), ensuring optimal depth and lateral positioning of NV- centers relative to the electric field anti-node. |
| Requirement: Ultra-flat surface for robust dielectric mirror deposition (SiO2/TiO2 and SiO2/Ta2O5) to achieve critical high reflectivity (R >99.99%). | Ultra-Precision Polishing (Ra < 1 nm) | 6CCVD guarantees Ra < 1 nm polishing on SCD surfaces, significantly reducing scattering losses and enabling the production of highly stable, high-Q optical cavities required to overcome the mechanical instability issues noted in the paper. |
| Requirement: Integration into complex microcavity structures (e.g., future photonic crystal integration or custom membrane thickness). | Custom Dimensions and Thin-Film SCD | We manufacture thin-film SCD down to 0.1 ”m thickness, perfect for creating diamond membranes that can be integrated into monolithic cavity structures or coupled to external optics with enhanced efficiency. |
| Future Requirement: Integration of electrical contacts or thermal dissipation layers (if high power CW is used). | In-House Metalization Services | 6CCVD offers internal, high-quality deposition of complex metal stacks, including Ti/Pt/Au, Pd, W, and Cu, critical for fabricating integrated quantum devices that require gate control or ohmic contacts. |
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house team of PhD material scientists and technical engineers specialize in optimizing diamond growth recipes and post-processing steps (polishing, metalization, defect creation readiness). We can provide expert consultation on material selection, doping concentration, and surface preparation to support projects aiming to transition solid-state NV- defects into high-performance, scalable quantum computing applications.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly. We ship globally (DDU default, DDP available).
View Original Abstract
We demonstrate the tunable enhancement of the zero phonon line of a single\nnitrogen-vacancy color center in diamond at cryogenic temperature. An open\ncavity fabricated using focused ion beam milling provides mode volumes as small\nas 1.24 $\mu$m$^3$. In-situ tuning of the cavity resonance is achieved with\npiezoelectric actuators. At optimal coupling of the full open cavity the signal\nfrom individual zero phonon line transitions is enhanced by about a factor of\n10 and the overall emission rate of the NV$^-$ center is increased by 40%\ncompared with that measured from the same center in the absence of cavity field\nconfinement. This result is important for the realization of efficient\nspin-photon interfaces and scalable quantum computing using optically\naddressable solid state spin qubits.\n