Optical levitation of nanodiamonds by doughnut beams in vacuum
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2017-03-01 |
| Journal | Laser & Photonics Review |
| Authors | Lei-Ming Zhou, Ke-Wen Xiao, Jun Chen, Nan Zhao, Lei-Ming Zhou |
| Institutions | Shanxi University, Beijing Computational Science Research Center |
| Citations | 38 |
| Analysis | Full AI Review Included |
Technical Analysis and Commercial Solutions Brief: MPCVD Diamond for High-Vacuum Optomechanics
Section titled âTechnical Analysis and Commercial Solutions Brief: MPCVD Diamond for High-Vacuum OptomechanicsâExecutive Summary
Section titled âExecutive SummaryâThe analyzed research proposes a novel solution for realizing stable, low-dissipation, hybrid spin-optomechanical systems in high vacuum by optically levitating composite core-shell nanodiamonds (ND core, Silica shell).
- Core Challenge Solved: Overcoming severe thermal damage and heating problems caused by the absorption of trapping laser energy by nanodiamond defects/graphitization in low-dissipation, high-vacuum environments (e.g., 10-6 Pa).
- Technique: Trapping a silica-coated nanodiamond core using highly focused doughnut beams (specifically, Azimuthally Polarized Gaussian or Linearly Polarized LG03 modes) which feature a dark intensity center.
- Thermal Suppression: Positioning the absorptive nanodiamond core in the dark region suppresses heat absorption by factors ranging from 102 up to 106 (depending on the beam mode and core size).
- Stability Achievement: This suppression allows the system to withstand high incident power (up to 1 Watt) without significant heating, enabling stable levitation necessary for quantum regimes.
- Performance Metrics: The system achieves ultra-high mechanical quality factors (Q) up to 1010 at pressures of 10-6 Pa, establishing a powerful platform for fundamental quantum physics experiments.
- Material Requirement: Success relies critically on high-purity nanodiamond material with integrated Nitrogen-Vacancy (NV) centers for the spin component, requiring precise MPCVD growth control.
Technical Specifications
Section titled âTechnical SpecificationsâThe following table summarizes the key physical and performance parameters demonstrated or modeled in the levitation experiment.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Diamond Core Status | Absorptive (Defects/Graphitization) | N/A | Requires NV centers (Spin) |
| Optimal Core Radius (r) | < 100 | nm | Key for strong suppression (l ≥ 3 modes) |
| Typical Shell Radius (R) | 0.5 - 2.0 | ”m | Required size range for stable trapping |
| Trapping Wavelength (λ) | 1064 | nm | Near-Infrared (NIR) |
| Numerical Aperture (NA) | 0.95 | N/A | Extremely strong focusing required |
| Maximum Incident Power (Pinc) | Up to 1 | Watt | Tolerated due to suppression |
| Target Residual Pressure (P) | 10-6 | Pa | Required for ultra-high Q factor |
| Mechanical Quality Factor (Q) | ≥ 1010 | N/A | Best figure of merit for optomechanics |
| Optimal Beam Modes | Azimuthally Polarized Gaussian / Linear LG03 | N/A | Provides absolute stable trapping regions |
| Absorption Suppression Ratio (Ο) | 10-2 to 10-6 | Ratio | Highly dependent on beam index (l) and core size |
| Optimal Trapping Frequency (Ω/2Ï) | ~100 | kHz | Achieved with Azimuthally Polarized beam |
Key Methodologies
Section titled âKey MethodologiesâThe study utilized a sophisticated theoretical approach combining advanced electrodynamics modeling to predict trapping stability and thermal performance in high vacuum.
- System Setup Modeling: A dual-beam optical tweezers system was modeled, using two incoherent counter-propagating laser beams focused by identical high-NA lenses (NA = 0.95).
- Beam Modeling: Strongly focused doughnut beams, including Linearly Polarized Laguerre-Gaussian (LG), Right Circularly Polarized LG (rcLG), and Azimuthally Polarized Gaussian (apG) beams, were modeled using the highly accurate Generalized Vector Debye Integral Theory.
- Core-Shell Particle Modeling: The absorption and scattering properties of the nanodiamond core and silica shell composite structure were calculated using Generalized Lorentz-Mie Theory (GLMT).
- Force Calculation: Time-averaged Maxwell Stress Tensor was used to calculate the optical force exerted on the sphere, enabling the determination of the trapping potential $U(x)$ and force constant matrix $K$.
- Trapping Stability Analysis: Stability diagrams were generated by calculating the complex eigenvalues of the force constant matrix $K$ and comparing them against the required critical damping coefficient ($\gamma_{c}$), focusing on absolutely stable regions (ASRs) where $\gamma$ = 0.
- Thermal Equilibrium Calculation: Equilibrium temperature (T) was estimated by balancing the absorbed laser power ($C_{abs} P_{inc}$) against black-body radiation loss ($\sigma AT^{4}$), neglecting residual gas surface conduction at ultra-low pressures.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research highlights the critical need for advanced diamond materials that can serve as the core spin-optomechanical component. 6CCVD is uniquely positioned to supply the requisite high-quality, custom MPCVD diamond necessary to replicate and extend this foundational work.
Applicable Materials
Section titled âApplicable MaterialsâTo achieve the low-absorption, high-coherence spin system required for this levitation platform, 6CCVD recommends:
- Single Crystal Diamond (SCD) Precursors: For the purest possible core material, optical-grade SCD wafers (or plates) are ideal. SCD offers the highest initial purity, minimizing intrinsic defects that contribute to heating ($K_{core}$ < 10-5).
- Controlled Nitrogen-Vacancy (NV) Integration: NV centers are the quantum component. 6CCVD can supply SCD or Polycrystalline Diamond (PCD) materials specifically engineered for NV integration, either through:
- In-situ Doping: Controlled nitrogen gas flow during MPCVD growth.
- Post-processing: Wafers/plates can be provided ready for external irradiation and annealing, ensuring precise control over NV depth and concentration.
- High-Purity Polycrystalline Diamond (PCD): Suitable for applications where larger volumes of core material are required, offering custom thicknesses up to 500 ”m and wafers up to 125 mm in diameter, which can be diced and processed into nanospheres.
Customization Potential
Section titled âCustomization PotentialâThe success of the core-shell levitation relies on precise particle geometry and purity, demanding customized precursors:
| Research Requirement | 6CCVD Custom Capability | Application Alignment |
|---|---|---|
| Ultra-thin Diamond Cores | SCD/PCD down to 0.1 ”m thickness. | Provides precise control over the mass and size of the precursor material for nanofabrication (e.g., R=100 nm particles). |
| Precise Geometry/Dicing | Laser cutting and dicing capabilities. | Fabrication of small, uniform precursor plates ready for mechanical or chemical processing into spheres/cores. |
| Ultra-Low Surface Roughness | SCD polishing to Ra < 1 nm. | Minimizes surface imperfections or graphitization [32] which significantly increase thermal absorption. |
| Specialized Thicknesses | Substrates up to 10 mm. | Thicker substrates available for complex fabrication steps or mounting fixtures related to the trapping optics. |
Engineering Support
Section titled âEngineering SupportâThe transition from theoretical optimization of laser modes (LG03, Azimuthal Gaussian) and particle geometry (core-shell R/r ratio) to a functioning experimental setup is highly complex.
6CCVDâs in-house team of PhD material scientists and technical engineers offers comprehensive support for similar spin-optomechanical levitation projects, specializing in:
- Material Selection Consultation: Advising on the optimal SCD or PCD grade based on required NV coherence time and maximum heat tolerance.
- NV Center Density Mapping: Characterizing nitrogen concentration uniformity across MPCVD grown wafers.
- Custom Metalization Schemes: While this paper focuses on optical trapping, 6CCVD offers custom metalization (Au, Pt, Ti, Cu, W, Pd) for ancillary electrode control, manipulation, or heating/cooling interfaces required in hybrid systems.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly. Global shipping (DDU default, DDP available) ensures rapid delivery to research institutions worldwide.
View Original Abstract
Abstract Optically levitated nanodiamonds with nitrogenâvacancy centers promise a highâquality hybrid spinâoptomechanical system. However, the trapped nanodiamond absorbs energy from laser beams and causes thermal damage in vacuum. It is proposed here to solve the problem by trapping a composite particle (a nanodiamond core coated with a less absorptive silica shell) at the center of strongly focused doughnutâshaped laser beams. Systematical study on the trapping stability, heat absorption, and oscillation frequency concludes that the azimuthally polarized Gaussian beam and the linearly polarized LaguerreâGaussian beam LG 03 are the optimal choices. With our proposal, particles with strong absorption coefficients can be trapped without obvious heating and, thus, the spinâoptomechanical system based on levitated nanodiamonds are made possible in high vacuum with the present experimental techniques. image