Spectral broadening and ultrafast dynamics of a nitrogen-vacancy center ensemble in diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-03-29 |
| Journal | Materials for Quantum Technology |
| Authors | Albert Liu, Steven T. Cundiff, Diogo B. Almeida, Ronald Ulbricht |
| Institutions | University of Michigan, Max Planck Institute for Polymer Research |
| Citations | 34 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Ultrafast Dynamics of NV Centers in Diamond
Section titled âTechnical Documentation & Analysis: Ultrafast Dynamics of NV Centers in DiamondâExecutive Summary
Section titled âExecutive SummaryâThis research successfully employed Multi-Dimensional Coherent Spectroscopy (MDCS) and Four-Wave Mixing (FWM) to isolate and characterize the fundamental decoherence mechanisms of Nitrogen-Vacancy (NV) center ensembles in bulk diamond at cryogenic temperatures. The findings provide critical insight necessary for engineering spectrally stable NV centers for quantum technologies.
- Core Achievement: Successfully circumvented inhomogeneous broadening in NV ensembles to measure the intrinsic homogeneous dephasing rate ($\gamma$) across a temperature range of 6 K to 140 K.
- Key Decoherence Mechanism: The primary Zero-Phonon Line (ZPL) dephasing mechanism was identified as a Jahn-Teller-induced vibronic state, characterized by a localized phonon mode energy ($E_{ph}$) of 34.41 meV.
- Intrinsic Performance: The intrinsic zero-temperature dephasing rate ($\gamma_0$) was determined to be 37.31 GHz, corresponding to an ensemble-averaged coherence time (T2) of 26.8 ps.
- Ultrafast Dynamics: Ultrafast spectral diffusion was observed (rates up to 1.98 MHz/ps), driven solely by resonant photo-excitation and subsequent reorganization of the surrounding diamond lattice.
- Sensing Potential: The observation of temperature-dependent Stark splitting of the excited orbital states suggests the feasibility of developing microwave-free, all-optical electric-field sensing protocols using NV ensembles.
- Material Requirement: The study relies on high-quality, bulk monocrystalline diamond (Type Ib) with controlled NV incorporation (1-2 ppm density).
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the MDCS and FWM measurements on the NV center ensemble:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Sample Material | Type Ib Bulk Diamond | N/A | Monocrystalline, NV ensemble |
| NV Center Density | 1 - 2 | ppm | Introduced via 1 MeV electron irradiation |
| ZPL Resonance Energy | 1946 (637) | meV (nm) | Zero-Phonon Line |
| Measurement Temperature Range | 6 to 140 | K | Cryogenic environment |
| Excitation Pulse Duration | 90 | fs | Used for MDCS/FWM |
| Laser Repetition Rate | 250 | kHz | Optical Parametric Amplifier (OPA) source |
| Zero-Temperature Dephasing Rate ($\gamma_0$) | 37.31 | GHz | Intrinsic homogeneous linewidth |
| Coherence Time (T2) | 26.8 | ps | Calculated as 1 / ($\pi \gamma_0$) |
| Involved Phonon Mode Energy ($E_{ph}$) | 34.41 | meV | Jahn-Teller vibronic A1 mode |
| Ultrafast Spectral Diffusion Rate | 1.59 to 1.98 | MHz/ps | Measured at 10 K, T increasing from 1 ps to 2 ns |
| Internal Electric Field Range | 0.29 to 0.43 | MV/cm | Corresponding to observed Stark splitting (50 K to 140 K) |
Key Methodologies
Section titled âKey MethodologiesâThe experiment utilized advanced nonlinear optical techniques to probe the ultrafast dynamics of the NV center ensemble:
- Sample Preparation: Type Ib bulk monocrystalline diamond was used. NV centers were created via 1 MeV electron irradiation followed by subsequent annealing, resulting in a controlled NV density of 1-2 ppm.
- Spectroscopy Technique: Multi-Dimensional Coherent Spectroscopy (MDCS) and Four-Wave Mixing (FWM) were performed using a three-pulse sequence ($\tau$, T, $t$) in a box geometry setup to generate a photon echo signal.
- Excitation Source: Three resonant laser pulses, approximately 90 fs in duration and generated by an Optical Parametric Amplifier (OPA) at 250 kHz, were centered on the NV ZPL (1946 meV).
- Signal Detection: The FWM photon echo signal was heterodyne detected using a separate local-oscillator pulse.
- Environmental Control: The sample was mounted to a cold-finger cryostat and maintained at cryogenic temperatures (6 K to 140 K) for temperature-dependent analysis.
- Dephasing Analysis: Fourier transformation of the FWM signal along the time delays yielded one-quantum spectra, allowing for the unambiguous separation of homogeneous ($\gamma$) and inhomogeneous ($\sigma$) broadening components.
- Spectral Diffusion Measurement: Waiting time (T) dependent measurements of the dephasing rate ($\gamma$) were used to quantify ultrafast spectral diffusion dynamics on the picosecond timescale.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe successful replication and extension of this quantum research require high-quality, low-strain diamond material with precise control over defect incorporation and surface termination. 6CCVD is uniquely positioned to supply the necessary MPCVD diamond substrates and engineering services.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate or extend the study of NV center dynamics, researchers require high-purity SCD material optimized for quantum applications:
- Optical Grade Single Crystal Diamond (SCD): The foundation of this research is bulk monocrystalline diamond. 6CCVD provides high-purity SCD substrates with extremely low nitrogen content (below 1 ppm) and low strain, which is critical for achieving the narrow optical linewidths necessary for stable quantum transitions.
- Controlled Defect Precursors: While the paper used post-growth irradiation, 6CCVD can supply SCD material with controlled, low concentrations of substitutional nitrogen (P1 centers) optimized for efficient NV- conversion via subsequent irradiation and annealing.
- Polycrystalline Diamond (PCD): For large-area sensing arrays or integrated photonics requiring larger wafers, 6CCVD offers high-quality PCD up to 125 mm in diameter, polished to an optical finish (Ra < 5 nm).
Customization Potential for Integrated Devices
Section titled âCustomization Potential for Integrated DevicesâThe paper highlights the potential for all-optical electric-field sensing, which often requires integrated diamond devices (e.g., waveguides or electrodes). 6CCVD offers comprehensive customization services:
| Requirement from Research | 6CCVD Capability | Technical Specification |
|---|---|---|
| Substrate Dimensions | Custom Plates/Wafers | Up to 125 mm (PCD), Custom SCD plates |
| Thickness Control | SCD and PCD Films | 0.1 ”m to 500 ”m (for thin film devices) |
| Surface Quality | Ultra-Low Roughness Polishing | Ra < 1 nm (SCD), Ra < 5 nm (PCD) |
| Integrated Sensing | Custom Metalization | Internal capability for Au, Pt, Pd, Ti, W, Cu |
| Device Integration | Laser Cutting & Shaping | Precision cutting for waveguides or resonators |
Engineering Support
Section titled âEngineering SupportâThe complex dynamics observed (Jahn-Teller effect, ultrafast spectral diffusion, Stark splitting) underscore the need for precise material engineering.
- Material Selection for Quantum Sensing: 6CCVDâs in-house PhD team specializes in optimizing MPCVD growth parameters to minimize lattice defects and strain, which are primary contributors to the inhomogeneous broadening and spectral diffusion observed in this study.
- Defect Engineering Consultation: We provide consultation on optimizing post-processing steps (e.g., irradiation dose and annealing temperature) to achieve the desired NV density (1-2 ppm) while maintaining high crystal quality, crucial for maximizing T2 coherence times.
- Global Logistics: 6CCVD ensures reliable global shipping (DDU default, DDP available) for sensitive quantum materials, minimizing delays in critical research timelines.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract Many applications of nitrogen-vacancy (NV) centers in diamond crucially rely on a spectrally narrow and stable optical zero-phonon line transition. Though many impressive proof-of-principle experiments have been demonstrated, much work remains in engineering NV centers with spectral properties that are sufficiently robust for practical implementation. To elucidate the mechanisms underlying their interactions with the environment, we apply multi-dimensional coherent spectroscopy to an NV center ensemble in bulk diamond at cryogenic temperatures. Our spectra reveal thermal dephasing due to quasi-localized vibrational modes as well as ultrafast spectral diffusion on the picosecond timescale. The intrinsic, ensemble-averaged homogeneous linewidth is found to be in the tens of GHz range by extrapolating to zero temperature. We also observe a temperature-dependent Stark splitting of the excited state manifold, relevant to NV sensing protocols.