Terahertz emission from diamond nitrogen-vacancy centers
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2024-05-29 |
| Journal | Science Advances |
| Authors | SĂĄndor Kollarics, Bence G. MĂĄrkus, Robin Kucsera, GergĆ Thiering, ĂdĂĄm Gali |
| Institutions | HUN-REN Wigner Research Centre for Physics, Institute for Solid State Physics and Optics |
| Citations | 10 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive Summaryâ- Core Achievement: Demonstrated the generation of coherent terahertz (THz) radiation (0.42 THz) using nitrogen-vacancy (NV) centers embedded in a single crystal diamond.
- Mechanism: Population inversion is achieved by combining selective optical pumping (532 nm laser) of the Sz = 0 sublevel and Zeeman splitting of the S=1 ground state triplet in a strong 15 T magnetic field.
- Coherence Confirmation: Phase-sensitive THz detection confirmed that the emitted photons are coherent with the incoming excitation, validating the potential for a solid-state THz maser (TASER).
- Tunability: The frequency of the THz emission is directly tunable by adjusting the external magnetic field strength.
- Spin Dynamics: The spin-lattice relaxation time (T1) remains long (milliseconds at room temperature) and is unaffected by the high magnetic fields (up to 15 T), which is crucial for maintaining efficient population inversion.
- Methodology: Utilized a highly sensitive, home-built High-Field/High-Frequency Electron Spin Resonance (HFESR) setup combined with a double lock-in Light-Induced ESR (LESR) technique for precise spin dynamics measurement.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Coherent Emission Frequency | 0.42 (and 0.21) | THz | Corresponds to Zeeman splitting at 15 T. |
| Magnetic Field (B) | 15 | T | Required for 0.42 THz population inversion. |
| NV Center Concentration | 12 | ppm | High concentration in Type Ib diamond sample. |
| Ground State Zero-Field Splitting (D/h) | 2.87 | GHz | Intrinsic splitting of the NV S=1 state. |
| Excitation Laser Wavelength | 532 | nm | Used for selective optical pumping. |
| Laser Intensity (Reaching Sample) | 1 | W/cm2 | Effective intensity for pumping. |
| Spin-Lattice Relaxation Time (T1) | ~4 | ms | Room temperature value; maintained up to 15 T. |
| HFESR Spectrometer Sensitivity | 3 x 1010 | spins / 10-4 TâHz | Optimized for phase-coherent detection. |
| ESR Operating Frequency Range | 0.052 to 0.420 | THz | Range of the HFESR instrument used. |
| Minimum Measurement Temperature | 2 | K | Used for temperature-dependent ESR studies. |
Key Methodologies
Section titled âKey Methodologiesâ- Sample Preparation: A Type Ib single crystal diamond plate (5 mm diameter) with 12 ppm NV concentration was used. The NV centers were created via electron beam irradiation followed by thermal annealing.
- High-Field Environment: The sample was placed inside a liquid helium variable temperature insert (VTI) within a superconducting solenoid capable of generating fields up to 16 T.
- Quasi-Optical Setup: Microwaves (near-THz) were directed to the sample via a corrugated waveguide, isolated by a thin Mylar sheet (low loss in THz and visible ranges).
- Optical Pumping: A 532 nm Nd:YAG laser (100 mW max incident power) was guided quasi-optically to the sample surface for continuous illumination and selective spin polarization.
- HFESR Detection: Reflected THz radiation was detected using a liquid helium-cooled InSb hot-electron bolometer in a homodyne single-ended mixer configuration, enabling phase-sensitive detection.
- Conventional ESR Measurement: Detected using magnetic field modulation (0.05 mT at 20 kHz) and a first lock-in amplifier (SR830).
- Light-Induced ESR (LESR) and T1 Measurement: The laser light was amplitude-modulated (chopped) at frequencies ranging from 1 to 400 Hz. A second lock-in amplifier, synchronized to the chopper, detected the change in the conventional ESR signal, allowing for the measurement of the spin-lattice relaxation time (T1).
Commercial Applications
Section titled âCommercial Applicationsâ- Broadband Communication: Development of tunable, coherent THz sources to fill the âTHz gapâ (0.1 to 10 THz), enabling next-generation high-speed wireless data transmission.
- Security and Medical Imaging: THz radiation is non-ionizing and highly sensitive to water content, making it valuable for advanced medical diagnostics and security screening systems.
- Quantum Amplification (TASER): The NV system, due to its long T1 time and efficient optical pumping, is a promising candidate for a solid-state, tunable THz maser (TASER) or high-frequency amplifier.
- Condensed Matter Research: Provides a coherent, tunable source necessary for fundamental studies of correlated electron systems, superconductors, density wave systems, and non-equilibrium dynamics.
- Spintronics and Quantum Sensing: The NV center is a leading platform for quantum metrology and magnetometry; this work enables high-field, high-frequency control necessary for advanced spintronic devices and quantum communication.
View Original Abstract
Coherent light sources emitting in the terahertz range are highly sought after for fundamental research and applications. Terahertz lasers rely on achieving population inversion. We demonstrate the generation of terahertz radiation using nitrogen-vacancy centers in a diamond single crystal. Population inversion is achieved through the Zeeman splitting of the S = 1 state in 15 tesla, resulting in a splitting of 0.42 terahertz, where the middle S z = 0 sublevel is selectively pumped by visible light. To detect the terahertz radiation, we use a phase-sensitive terahertz setup, optimized for electron spin resonance (ESR) measurements. We determine the spin-lattice relaxation time up to 15 tesla using the light-induced ESR measurement, which shows the dominance of phonon-mediated relaxation and the high efficacy of the population inversion. The terahertz radiation is tunable by the magnetic field, thus these findings may lead to the next generation of tunable coherent terahertz sources.