Characterization of the angular-dependent emission of nitrogen-vacancy centers in nanodiamond
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2020-09-18 |
| Journal | Applied Physics B |
| Authors | Justus Christinck, Beatrice Rodiek, Marco López, Helmuth Hofer, Hristina Georgieva |
| Institutions | Physikalisch-Technische Bundesanstalt, Technische Universität Braunschweig |
| Citations | 10 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”This research focuses on the detailed characterization and modeling of single nitrogen-vacancy (NV-) centers in nanodiamonds (NDs) to advance the realization of a deterministic absolute single-photon source.
- Core Achievement: Successfully determined the 3D orientation (out-of-plane angle θ and in-plane angle φ) of single NV-centers in nanodiamonds using two independent experimental methods.
- Method Validation: Orientation results derived from Back Focal Plane Imaging (BFPI) showed strong agreement with results derived from Photoluminescence (PL) intensity dependence on laser polarization angle.
- Theoretical Model: A theoretical model based on Lukosz’s work was developed to calculate the angular emission patterns of two perpendicular dipoles (NV-center) at a dielectric interface (ND/cover glass).
- Single-Photon Purity: The investigated NV-center was confirmed as a single-photon emitter with a measured second-order correlation function g(2)(τ=0) = 0.09.
- Collection Efficiency (CE): Using the angular emission model, the calculated collection efficiency for the high NA (1.45) objective was determined to be high, ranging from 80% to 83%, depending on the NV-center orientation.
- Engineering Impact: This work provides the necessary tools (model and methods) for calculating and optimizing the collection efficiency of single-photon sources, a critical step for quantum metrology and communication applications.
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| Nanodiamond Diameter (Average) | 75 | nm | GAF 0.15 microdiamond AG sample |
| Excitation Laser Wavelength | 532 | nm | Used for NV-center excitation |
| Objective Numerical Aperture (NA) | 1.45 | - | Oil immersion objective (100x) |
| Zero-Phonon Line (ZPL) | 637 | nm | Confirms NV- center negative charge state |
| Second Order Correlation g(2)(τ=0) | 0.09 | - | Confirms single-photon emission purity |
| NV-Center Emission Lifetime | 12.2 | ns | Measured value |
| Calculated Collection Efficiency (CE) Range | 80 to 83 | % | Dependent on NV-center orientation (θ=0° to θ=90°) |
| NV-Center 1 Orientation (BFPI) | 70 / 345 | ° / ° | Out-of-plane (θ) / In-plane (φ) |
| NV-Center 1 Orientation (PL Polarization) | 60 / 334 | ° / ° | Out-of-plane (θ) / In-plane (φ) |
| Estimated Dipole Height (z0) | 60 | nm | Distance between dipoles and the dielectric interface |
| Bertrand Lens Focal Length | 500 | mm | Used for Back Focal Plane Imaging |
Key Methodologies
Section titled “Key Methodologies”- Sample Preparation and Setup: Nanodiamonds (75 nm) containing NV-centers were spin-coated onto a cover glass. The sample was investigated using a confocal laser-scanning microscope setup with a 532 nm excitation laser and a high NA (1.45) oil immersion objective.
- Single-Photon Confirmation: The single-photon purity was verified using a Hanbury Brown and Twiss (HBT) interferometer setup, measuring the second-order correlation function g(2)(τ).
- Back Focal Plane Imaging (BFPI): A Bertrand lens and a tube lens were introduced into the fluorescence path to image the angular emission pattern onto an sCMOS camera.
- Orientation Determination via BFPI: The measured BFPI image was compared against a calculated image derived from the theoretical Lukosz model. The in-plane angle (φ) was determined from the axis of symmetry in the BFPI image, and the out-of-plane angle (θ) was determined from the location of the minimum intensity.
- Orientation Determination via PL Polarization: The photoluminescence intensity was measured as the linear polarization angle (δ) of the excitation laser was rotated. The NV-center orientation angles (θ and φ) were derived from the ratio of minimum (Imin) to maximum (Imax) fluorescence intensity.
- Collection Efficiency Calculation: The theoretical angular emission patterns (P(s) and P(p) for s- and p-waves) were numerically integrated over the objective’s opening angle (α0) to calculate the total collection efficiency (CE) as a function of the NV-center out-of-plane angle (θ).
Commercial Applications
Section titled “Commercial Applications”The characterization and optimization of NV-center emission are foundational for several high-tech industries, particularly those requiring robust, deterministic quantum emitters.
- Quantum Metrology and Standards: Establishing deterministic absolute single-photon sources traceable to national standards, closing the gap between traditional and quantum radiometry.
- Quantum Communication (QKD): Providing stable, room-temperature single-photon sources necessary for secure quantum key distribution networks.
- Quantum Computing: NV-centers serve as solid-state qubits, and efficient photon collection is crucial for spin readout and entanglement operations.
- Advanced Microscopy and Imaging: The BFPI technique is essential for characterizing the orientation of single emitters (including SiV, SnV, and hBN centers) used in super-resolution imaging and material science.
- Nanoscale Sensing: Optimizing photon collection efficiency directly enhances the signal-to-noise ratio for NV-center-based sensors used in magnetic field, electric field, and temperature measurements at the nanoscale.
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.