Characterization of the angular-dependent emission of nitrogen-vacancy centers in nanodiamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-09-18 |
| Journal | Applied Physics B |
| Authors | Justus Christinck, Beatrice Rodiek, Marco LĂłpez, Helmuth Hofer, Hristina Georgieva |
| Institutions | Technische UniversitÀt Braunschweig, Physikalisch-Technische Bundesanstalt |
| Citations | 10 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Angular-Dependent NV-Center Emission
Section titled âTechnical Documentation & Analysis: Angular-Dependent NV-Center EmissionâThis document analyzes the research paper âCharacterization of the angular-dependent emission of nitrogen-vacancy centers in nanodiamondâ to provide technical specifications and highlight how 6CCVDâs advanced MPCVD diamond materials and fabrication services can support and extend this critical work in quantum optics and metrology.
Executive Summary
Section titled âExecutive SummaryâThe research successfully characterizes the angular emission profile of single nitrogen-vacancy (NV-) centers in nanodiamonds, a crucial step toward realizing deterministic, absolute single-photon sources (SPS).
- Deterministic Source Validation: NV-centers in nanodiamonds were confirmed as robust, room-temperature single-photon emitters suitable for quantum metrology applications.
- Orientation Determination: The orientation of the NV-center axis ($\theta, \phi$) was accurately determined by comparing theoretical models of angular emission patterns with experimental back focal plane (BFP) imaging and polarization-dependent fluorescence measurements.
- High Collection Efficiency (CE): The experimental setup achieved a calculated collection efficiency ranging from 80% to 83%, demonstrating near-optimal photon collection based on the NV-center orientation.
- Single-Photon Purity: Single-photon emission was verified using Hanbury-Brown and Twiss (HBT) interferometry, yielding a high purity value of $g^{(2)}(\tau=0) = 0.09$.
- Model Consistency: The determined NV-center orientations derived from BFP imaging ($\theta=70^\circ, \phi=345^\circ$) and absorption dipole measurements ($\theta=60^\circ, \phi=334^\circ$) showed satisfactory agreement, validating the BFP imaging technique for orientation analysis.
- Future Platform Requirements: The work identifies the need for high-quality diamond platforms to integrate next-generation color centers (SiV, SnV) and optimize collection efficiency through interface engineering.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental results and theoretical calculations:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Nanodiamond Diameter (Average) | 75 | nm | GAF 0.15 microdiamond AG |
| Excitation Wavelength | 532 | nm | Confocal laser-scanning setup |
| Objective Numerical Aperture (NA) | 1.45 | N/A | Oil immersion microscope objective (100x) |
| Zero-Phonon Line (ZPL) | 637 | nm | Characteristic of NV- center emission |
| Second-Order Correlation ($g^{(2)}(\tau=0)$) | 0.09 | N/A | Confirms high single-photon purity |
| NV-Center Emission Lifetime | 12.2 | ns | Measured via three-level model fit |
| Calculated Collection Efficiency (CE) Range | 80 - 83 | % | Dependent on NV-center out-of-plane angle ($\theta$) |
| NV-Axis Orientation ($\theta$) (BFP Imaging) | 70 | ° | Out-of-plane angle (NV-center 1) |
| NV-Axis Orientation ($\phi$) (BFP Imaging) | 345 | ° | In-plane angle (NV-center 1) |
| Estimated Dipole Height ($z_{0}$) | 60 | nm | Above the dielectric interface (consistent with ND size) |
Key Methodologies
Section titled âKey MethodologiesâThe experimental approach combined advanced confocal microscopy with theoretical modeling to characterize the NV-center emission properties:
- Sample Fabrication: Nanodiamonds (75 nm average diameter) containing NV-centers were spin-coated onto a cover glass, forming the dielectric interface for emission analysis.
- Confocal Excitation: A 532 nm laser was used to excite the NV-centers through a high Numerical Aperture (NA 1.45) oil immersion objective.
- Single-Photon Verification: A Hanbury Brown and Twiss (HBT) setup was used to measure the second-order correlation function $g^{(2)}(\tau)$, confirming single-photon emission purity.
- Back Focal Plane (BFP) Imaging: A switchable mirror and a Bertrand lens (f = 500 mm) were introduced into the fluorescence path to image the angular emission pattern (Fourier transform of the angular emission) onto an sCMOS camera.
- Orientation Determination (BFP): The measured BFP image was compared against a theoretical Lukosz model, which accounts for the dipole emission near a dielectric interface, to derive the NV-center orientation ($\theta, \phi$) and dipole height ($z_{0}$).
- Orientation Determination (Polarization): Photoluminescence intensity was measured as a function of the excitation laser polarization angle ($\delta$). The resulting minimum and maximum intensities ($I_{min}, I_{max}$) were used to calculate the out-of-plane angle $\theta = \cos^{-1} (\sqrt{I_{min} / I_{max}})$, providing a cross-validation of the BFP method.
- Collection Efficiency Calculation: The angular-dependent emission formulas were numerically integrated over the objectiveâs opening angle ($\alpha_{0}$) to calculate the collection efficiency (CE) as a function of the NV-center orientation $\theta$.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research demonstrates the critical role of material interfaces and precise orientation control in maximizing the performance of quantum emitters. 6CCVD provides the necessary high-purity diamond substrates and advanced fabrication capabilities required to transition this research from nanodiamonds on glass to robust, integrated solid-state quantum devices.
| Research Requirement / Challenge | 6CCVD Solution & Capability | Technical Advantage |
|---|---|---|
| High-Purity Substrates for Color Centers | Optical Grade Single Crystal Diamond (SCD) | Provides the ideal platform for deterministic quantum sources (NV, SiV, SnV). Our SCD features ultra-low nitrogen content (below 1 ppb), minimizing background noise and ensuring high coherence times for implanted or grown color centers. |
| Interface Optimization & Low Scattering | Ultra-Low Roughness Polishing | SCD plates are polished to achieve surface roughness (Ra) < 1 nm. This is essential for minimizing scattering losses, maximizing coupling efficiency into high-NA objectives, and enabling precise fabrication of solid immersion lenses (SILs) or photonic structures. |
| Custom Device Integration & Structuring | Custom Dimensions and Thickness Control | We supply SCD and PCD plates with custom thicknesses (0.1 ”m to 500 ”m) and large areas (PCD up to 125 mm). This supports advanced fabrication techniques like etching, bonding, and heterostructure integration required for high-CE quantum devices. |
| Enhancing Collection Efficiency (CE) | Custom Metalization Services | Internal capability for depositing reflective and conductive layers (Au, Pt, Pd, Ti, W, Cu). Metalization can be used to create back-mirrors or electrical contacts directly on the diamond substrate, significantly boosting photon collection efficiency, as modeled in the paper. |
| Scaling Quantum Sensor Arrays | Large-Area Polycrystalline Diamond (PCD) | For applications requiring large-scale quantum sensing or metrology arrays, our inch-size PCD wafers (up to 125 mm) offer excellent uniformity and surface quality (Ra < 5 nm). |
| Support for Next-Gen Emitters (SiV, SnV) | Expert Engineering Support | Our in-house PhD material scientists specialize in MPCVD growth parameters and post-processing techniques necessary for optimizing alternative color centers (Silicon-Vacancy, Tin-Vacancy) mentioned in the paperâs conclusion. |
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract We report on the characterization of the angular-dependent emission of single-photon emitters based on single nitrogen-vacancy (NV-) centers in nanodiamond at room temperature. A theoretical model for the calculation of the angular emission patterns of such an NV-center at a dielectric interface will be presented. For the first time, the orientation of the NV-centers in nanodiamond was determined from back focal plane images of NV-centers and by comparison of the theoretical and experimental angular emission pattern. Furthermore, the orientation of the NV-centers was also obtained from measurements of the fluorescence intensity in dependence on the polarization angle of the linearly polarized excitation laser. The results of these measurements are in good agreement. Moreover, the collection efficiency in this setup was calculated to be higher than 80% using the model of the angular emission of the NV-centers.