Thermometry of an optically levitated nanodiamond
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2022-07-01 |
| Journal | AVS Quantum Science |
| Authors | François Rivière, Timothée de Guillebon, Léo Maumet, G. Hétet, Martin Schmidt |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”This study utilizes the Nitrogen-Vacancy (NV) centers within levitated nanodiamonds (NDs) as highly sensitive thermometers to characterize material absorption properties at the single-nanoparticle level.
- Core Achievement: Measured the absorption cross-section (σabs) of single levitated NDs under Near-Infrared (NIR) trapping laser illumination (1550 nm).
- Absorption Mechanism: The absorption is confirmed to be extrinsic (due to defects/impurities) and volume-dominated, scaling proportionally to the particle radius cubed (rhydro3).
- Material Quality Assessment: The estimated bulk absorption coefficient (4 to 662 cm-1) is orders of magnitude greater than the expected value for ultra-pure diamond (< 0.01 cm-1), highlighting the critical need for material optimization.
- Thermometry Calibration: The temperature dependence of the NV center Zero Field Splitting, D(T), was calibrated for the specific ND batch up to 411 K, achieving a mean temperature uncertainty of ΔT = 2.0 K.
- Platform Value: Optical levitation is demonstrated as a unique, powerful platform for characterizing thermal properties and absorption mechanisms in materials at the nanoscale, independent of bulk measurements.
- Relevance to Quantum: This work provides essential data for optimizing diamond material, which is a critical step toward realizing stable, low-heating quantum spin-levitodynamics experiments.
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| Trapping Laser Wavelength (IR) | 1550 | nm | Primary heating source for levitation. |
| NV Excitation Wavelength (Green) | 532 | nm | Used for spin readout (photoluminescence). |
| Nanodiamond Type | FND-br100 (Bitotech) | N/A | Heavily doped, used for experiments. |
| Nitrogen Impurity Concentration | ~200 | ppm | High impurity level in the studied NDs. |
| NV Center Concentration | ~2 | ppm | Spin defects used for internal thermometry. |
| Calibration Temperature Range | 293 to 411 | K | Range used to calibrate D(T) response. |
| Maximum Stable Temperature | ~650 | K | Temperature limit before particle loss from the trap. |
| Operating Gas Pressure Range | 15 to 45 | mbar | Stability region for levitation experiments. |
| Mean Temperature Uncertainty (ΔT) | 2.0 | K | Uncertainty in temperature determination via D(T). |
| ESR Linewidth (Γ) | ~10 | MHz | Observed for HPHT diamonds near ambient T. |
| D(T) Derivative (dD/dT) | -74 | kHz/K | Sensitivity of the NV thermometer near ambient T. |
| Estimated Bulk Absorption Coefficient | 4 to 662 | cm-1 | Calculated from σabs, confirming high extrinsic absorption. |
| Intrinsic Diamond Absorption Limit | < 0.01 | cm-1 | Expected absorption for ultra-pure diamond at 1550 nm. |
| Absorption Cross-Section Scaling (σabs) | Proportional to rhydro3 | N/A | Confirms volume-dominated absorption mechanism. |
| Diamond Density (ρdiam) | ~3500 | Kg/m3 | Used in hydrodynamic radius calculation. |
Key Methodologies
Section titled “Key Methodologies”The study employed a two-stage methodology: NV thermometry calibration followed by single-particle levitation and thermal analysis.
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NV Thermometry Calibration (D(T)):
- Nanodiamonds were spin-coated onto a quartz coverslip placed on a heater stack.
- The temperature was controlled via a PID device coupled to a Pt100 sensor.
- Electron Spin Resonance (ESR) spectra were measured under 532 nm excitation across a temperature range (293 K to 411 K).
- The Zero Field Splitting (D) was extracted and fitted to a known polynomial function (Toyli et al.) to establish the D(T) relationship specific to the ND batch, correcting for internal strain (Dstrain).
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Single-Particle Levitation and Heating:
- A single nanodiamond was trapped in a vacuum chamber using a high-NA objective and a high-power 1550 nm IR laser.
- The chamber pressure (pgas) was maintained in the free-molecular regime (15 to 45 mbar).
- The internal temperature (Tint) was measured by performing ESR on the levitated ND at various IR laser power densities (Ilas).
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Thermal Analysis and Absorption Calculation:
- The particle damping coefficient (Γ) was measured from the particle dynamics Power Spectral Density (PSD) to determine the effective hydrodynamic radius (rhydro).
- Tint was modeled based on the balance between absorbed power (Pabs = σabsIlas) and gas conduction cooling (Pcond), yielding the heating coefficient (βheat).
- The measured βheat was used, along with rhydro, to calculate the absorption cross-section (σabs) for over 40 nanodiamonds.
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Mechanism Assessment:
- The calculated σabs was plotted against rhydro. A best fit confirmed a scaling proportional to rhydro3, demonstrating that absorption is dominated by volume effects rather than surface effects (which would scale as rhydro2).
Commercial Applications
Section titled “Commercial Applications”This research is highly relevant to industries requiring precise thermal management and defect engineering in nanoscale materials, particularly for quantum technologies.
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Quantum Sensing and Computing:
- Spin-Levitodynamics: Essential for optimizing diamond material used in hybrid spin-mechanics experiments, where heating severely limits coherence and stability. Requires ultra-low absorption NDs (e.g., CVD-grown ultra-pure diamond).
- NV Center Thermometry: Provides a robust, non-contact method for measuring localized temperatures in micro- and nano-devices.
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Advanced Materials Characterization:
- Nanoparticle Quality Control: Optical levitation offers a unique platform to characterize extrinsic defects (impurities, dislocations) and absorption coefficients in single nanoparticles, which is impossible using bulk methods.
- Defect Engineering: The ability to link absorption directly to volume defects guides the development of cleaner synthesis methods (e.g., high-purity CVD diamond growth) to minimize heating.
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High-Power Optics and Thermal Management:
- NIR Component Design: Provides fundamental data on the absorption properties of diamond in the critical 1550 nm telecommunications and high-power laser window.
- Micro-Device Cooling: Insights into gas conduction cooling mechanisms in the free-molecular regime are valuable for thermal modeling of micro- and nano-scale devices operating in low-pressure environments.
View Original Abstract
Using the spin properties of nitrogen-vacancy (NV) centers in levitated diamonds, we characterize the absorption of single nanodiamonds. We first calibrate the thermometry response of the NV centers embedded in our nanodiamonds. Then, using this calibration, we estimate the absorption cross-section of single levitated nanodiamonds. We show that this absorption is extrinsic and dominated by volumic effects. Our work opens the way to diamond material optimization for levitation quantum experiments. It also demonstrates optical levitation as a unique platform to characterize material thermal properties at the nanoparticle level.