| Metadata | Details |
|---|
| Publication Date | 2022-10-19 |
| Journal | Nanophotonics |
| Authors | Harini Hapuarachchi, Francesco Campaioli, Jared H. Cole |
| Institutions | RMIT University, Quantum (Australia) |
| Citations | 13 |
| Analysis | Full AI Review Included |
- Core Challenge Addressed: The primary limitation for Nitrogen-Vacancy (NV-) center quantum sensing is the low optical brightness and poor collection efficiency of the defects.
- Solution: A rigorous theoretical model is developed to describe the interaction between NV centers and Plasmonic Metal Nanoparticles (MNPs), demonstrating robust control and enhancement of NV emission.
- Model Novelty: The model extends existing isolated NV optical models by incorporating 3E vibronic contributions, accounting for both local electric field and decay rate modifications induced by the MNP, and solving the nonlinear open quantum system using a piecewise superoperator procedure.
- Validation Success: The model quantitatively explains existing experimental results, replicating the observed ~6x total NV emission enhancement and a Zero-Phonon Line (ZPL) decay rate enhancement of ~7.6x for an optimal NV-AuNP dimer configuration.
- Control Mechanisms: NV fluorescence can be actively controlled (enhanced or suppressed) by manipulating the NV orientation (parallel vs. perpendicular to the MNP surface), MNP size, NV-MNP separation, submerging medium permittivity, and the polarization/wavelength of the incoming light.
- Future Impact: This work provides a pathway for designing new plasmonic structures to significantly improve readout efficiencies, enabling higher precision, greater bandwidth quantum sensors, and novel readout modalities for quantum computing.
| Parameter | Value | Unit | Context |
|---|
| Emitter Type | Nitrogen-Vacancy (NV-) center | - | Solid-state quantum emitter in diamond. |
| Operating Condition | Room Temperature | - | Hybrid structures maintain stability at ambient conditions. |
| Gold Nanoparticle (AuNP) Radius (rm) | 30 | nm | Used for modeling optimal experimental configuration [3]. |
| NV-AuNP Center Separation (R) | 38 | nm | Optimal separation for maximum enhancement modeled. |
| Total Decay Rate Enhancement | ~6.5 | x | Modeled near-field enhancement (NV+MNP configuration). |
| ZPL Decay Rate Enhancement | ~7.6 | x | Modeled enhancement specific to the Zero-Phonon Line. |
| Far-Field Emission Enhancement (Observed) | ~6 | x | Experimentally reported enhancement for optimal dimer [3]. |
| Dimer Quantum Efficiency (QE) | ~0.78 | - | Estimated for the optimal NV-AuNP configuration. |
| Standard Input Laser Wavelength | 532 | nm | Green laser used for excitation. |
| Polarization Dependence | Proportional to sin2(θ) | - | Emission intensity dependence on excitation angle θ. |
| Submerging Media Tested | Air, Water, PMMA | - | Used to analyze the effect of medium permittivity (εb). |
- NV Center Optical Abstraction: The NV center is modeled as a multi-level atom, incorporating the 3A2 ground state (with n+1 vibronic levels) and the 3E excited state (with the zero phonon level |e0> and an effective upper excited level |e1> resonant with incoming radiation).
- Hamiltonian Formulation: A laboratory reference frame NV Hamiltonian is constructed, assuming dipole-dipole interaction between the NV center and the MNP. This formulation explicitly includes the nonlinear self-feedback field component (Etot(3)+).
- Effective Field Calculation: The total effective electric field (Etot) experienced by the NV center is calculated as the superposition of the screened external field (Etot(1)+) and the MNP direct dipole response field (Etot(2)+).
- MNP Modeling: The polarizability α(ωd) of small MNPs is determined using the Generalized Nonlocal Optical Response (GNOR) theory, which accounts for finite size effects crucial at nanoscale separations.
- Open Quantum System Solution: The nonlinear evolution of the NV density matrix is solved in a rotating reference frame using a Lindblad master equation approach. This solution is achieved via a computationally efficient piecewise superoperator procedure.
- Decoherence and Rate Modification: All relevant decoherence mechanisms (radiative, nonradiative, dephasing) are included, alongside modifications to both the local electric field and the emission decay rates induced by the proximal MNP.
- Control Parameter Sweeps: Systematic simulations were performed by varying the NV orientation (NV+MNP vs. NV||MNP), MNP radius (rm), center separation (R), submerging medium permittivity (εb), and input wavelength (resonant vs. off-resonant) to map emission control capabilities.
- Quantum Sensing (Enhanced Readout):
- Enables the development of next-generation, high-sensitivity quantum sensors (magnetometers, electrometers, thermometers) by significantly boosting the optical readout signal-to-noise ratio.
- Quantum Information Technology:
- Provides robust, room-temperature building blocks for quantum information processing and communication networks by creating stable, bright, single-photon sources.
- Bio-Sensing and Medical Imaging:
- NV-AuNP nanohybrids are highly promising due to the biocompatibility of both components (nanodiamonds and gold).
- The enhanced NV emission resides in the near-infrared therapeutic window (650-900 nm), allowing for deep tissue penetration in bio-sensing and biomarking applications.
- Nanophotonics and Optoelectronics:
- Utilizing high quality factor MNPs (like Silver) to create nanoscale optoelectronic devices that leverage large emission enhancements achievable when illuminated at plasmon resonance.
- Advanced Readout Modalities:
- Investigating strongly-nonlinear NV-plasmonic dynamics to develop new, initial-state-dependent readout modalities, potentially enhancing the discrimination capabilities of quantum sensors.
View Original Abstract
Abstract The nitrogen-vacancy (NV) center in diamond is very sensitive to magnetic and electric fields, strain, and temperature. In addition, it is possible to optically interrogate individual defects, making it an ideal quantum-limited sensor with nanoscale resolution. A key limitation for the application of NV sensing is the optical brightness and collection efficiency of these defects. Plasmonic resonances of metal nanoparticles have been used in a variety of applications to increase the brightness and efficiency of quantum emitters, and therefore are a promising tool to improve NV sensing. However, the interaction between NV centers and plasmonic structures is largely unexplored. In particular, the back-action between NV and plasmonic nanoparticles is nonlinear and depends on optical wavelength, nanoparticle position, and metal type. Here we present the general theory of NV-plasmonic nanoparticle interactions. We detail how the interplay between NV response, including optical and vibrational signatures, and the plasmonic response of the metal nanoparticle results in modifications to the emission spectra. Our model is able to explain quantitatively the existing experimental measurements of NV centers near metal nanoparticles. In addition, it provides a pathway to developing new plasmonic structures to improve readout efficiencies in a range of applications for the NV center. This will enable higher precision sensors, with greater bandwidth as well as new readout modalities for quantum computing and communication.