Localized nitrogen-vacancy centers generated by low-repetition rate fs-laser pulses
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2022-10-07 |
| Journal | Diamond and Related Materials |
| Authors | Charlie Oncebay, Juliana M. P. Almeida, Gustavo F. B. Almeida, Sérgio Ricardo Muniz, Cléber Renato Mendonça |
| Institutions | National University of Engineering, Universidade Federal de UberlĂąndia |
| Citations | 4 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive Summaryâ- Core Achievement: Demonstrated the successful generation of localized Nitrogen-Vacancy (NV-) centers in type-Ib CVD diamond using a low-repetition rate (1 kHz) femtosecond (fs) laser system (150 fs, 775 nm).
- Optimal Processing Parameters: Identified the optimal irradiation conditions for active NV center creation with minimal surface damage: a pulse fluence of 14 mJ/cm2 and laser focus positioned 15 to 20 ”m above the sample surface.
- Damage Threshold: Determined the diamond surface damage threshold fluence (Fth) to be 1.3 ± 0.1 mJ/cm2 using a 1.25 NA objective.
- Stochastic Generation: Confirmed that NV center density generally increases with the number of fs-pulses, but the generation process remains stochastic, depending heavily on the local structure and nitrogen impurity distribution.
- Strain Detection (Critical Finding): Optically Detected Magnetic Resonance (ODMR) spectra exhibited a broad dual-dip separated by approximately 25 MHz at zero external magnetic field.
- Implication of Strain: This dual-dip feature is attributed to significant permanent lattice strain induced during the fs-laser irradiation, which shifts and broadens the electron-spin resonance, potentially jeopardizing the use of these defects in high-coherence quantum information applications.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Diamond Material | Type-Ib synthetic | 5x5x1 mm3 | CVD grown, N impurity < 1 ppm |
| Laser Pulse Duration | 150 | fs | Ti:sapphire (Clark-MXR) source |
| Laser Wavelength | 775 | nm | Excitation wavelength |
| Laser Repetition Rate | 1 | kHz | Low-repetition rate operation |
| Damage Threshold Fluence (Fth) | 1.3 ± 0.1 | mJ/cm2 | Determined using the zero-damage method |
| Optimal Fluence (Minimal Damage) | 14 | mJ/cm2 | Used for focusing and pulse number studies |
| Optimal Focus Position (Z) | 15 to 20 | ”m | Above sample surface (Positive Z) |
| Sample Translation Speed | 10 | ”m/s | Constant speed during line fabrication |
| Annealing Temperature | 680 | °C | Post-irradiation processing |
| Annealing Time | 30 | minutes | To mobilize vacancies and remove carbon |
| Diamond Raman Peak | 1332 | cm-1 | First-order Raman peak (sp3 carbon) |
| NV0 Zero-Phonon Line (ZPL) | 2010 | cm-1 (574 nm) | Neutral charge state detection |
| NV- ZPL Wavelength | 637 | nm | Negative charge state detection (1.945 eV) |
| ODMR Resonance Frequency | ~2870 | MHz | Ground state transition (ms = 0 to ms = ±1) |
| ODMR Dual-Dip Separation | ~25 | MHz | Zero-field splitting attributed to lattice strain |
Key Methodologies
Section titled âKey Methodologiesâ- Material Selection: Used a low-nitrogen concentration (less than 1 ppm) type-Ib synthetic diamond grown via Chemical Vapor Deposition (CVD).
- Fs-Laser Irradiation:
- Used 150 fs pulses at 775 nm and 1 kHz repetition rate.
- Lines were fabricated by translating the sample at 10 ”m/s while varying pulse fluence (1.3 to 34 mJ/cm2) and objective Numerical Aperture (NA=1.25 or NA=0.85).
- Spots were irradiated at fixed fluence (14 mJ/cm2) and focus position (Z = +15 ”m) while varying the number of pulses (2k to 64k) to study defect density.
- Post-Irradiation Processing:
- Annealing: Sample was annealed at 680 °C for 30 minutes to remove amorphous carbon generated during ablation and increase vacancy mobility.
- Cleaning: Sample was cleaned using a 1:1:1 mixture of hydrochloric acid, nitric acid, and sulfuric acid to remove surface impurities.
- Optical Characterization:
- Fluorescence Microscopy: Used a commercial confocal system (Zeiss LSM-780, 543 nm excitation) and a homebuilt setup (532 nm excitation) to map fluorescent defects (600-800 nm emission range).
- Raman Spectroscopy: Performed using a 514 nm Argon laser to confirm the diamond lattice structure (1332 cm-1 peak) and detect the NV0 center (2010 cm-1 peak).
- Quantum State Analysis (ODMR):
- Optically Detected Magnetic Resonance (ODMR) was conducted at room temperature (300 K) without an external magnetic field.
- The microwave frequency was swept around 2.8 GHz to monitor the change in fluorescence corresponding to the electron spin resonance (ESR) of the NV- center.
Commercial Applications
Section titled âCommercial Applicationsâ- Quantum Sensing and Metrology: NV centers are leading solid-state quantum sensors capable of detecting magnetic fields, electric fields, and temperature at the nanoscale. This localized fabrication method is essential for creating high-density sensor arrays.
- Integrated Quantum Photonics: The ability to precisely position NV centers allows for the integration of these spin qubits into diamond photonic circuits (e.g., waveguides and resonators), crucial for scalable quantum devices and frequency conversion applications.
- Solid-State Qubits: NV centers are robust, room-temperature qubits. Controlled production methods, like the fs-laser technique, are vital for engineering controlled ensembles or single NV centers for quantum computing and quantum simulation platforms.
- Nanofabrication and Defect Engineering: This methodology provides a non-traditional, mask-less approach to microfabrication, allowing for the creation of spatially localized defects in diamond, which can be applied to other wide-bandgap semiconductors for novel device architectures.
- Strain-Tuned Quantum Devices: Although the induced strain was identified as a challenge, controlled laser-induced strain can potentially be used to tune the electronic and spin properties of NV centers, opening avenues for strain-mediated quantum control.
Tech Support
Section titled âTech SupportâOriginal Source
Section titled âOriginal SourceâReferences
Section titled âReferencesâ- 2009 - The âtypeâ classification system of diamonds and its importance in gemology (vol 45, pg 96, 2009)
- 1997 - Electron paramagnetic resonance imaging of the distribution of the single substitutional nitrogen impurity through polycrystalline diamond samples grown by chemical vapor deposition [Crossref]
- 2011 - Properties of nitrogen-vacancy centers in diamond: the group theoretic approach [Crossref]
- 2010 - Optical properties of the nitrogen-vacancy singlet levels in diamond [Crossref]
- 2006 - Single defect centres in diamond: a review [Crossref]
- 2006 - Processing quantum information in diamond [Crossref]
- 2006 - Room-temperature coherent coupling of single spins in diamond [Crossref]
- 2013 - Quantum logic readout and cooling of a single dark electron spin [Crossref]
- 2013 - Heralded entanglement between solid-state qubits separated by three metres [Crossref]