Diamond‐based concept for combining beams at very high average powers (Laser Photonics Rev. 11(3)/2017)
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2017-05-01 |
| Journal | Laser & Photonics Review |
| Authors | Aaron McKay, David J. Spence, David W. Coutts, Richard P. Mildren |
| Analysis | Full AI Review Included |
Technical Documentation and Analysis: Diamond for High-Power Beam Combination
Section titled “Technical Documentation and Analysis: Diamond for High-Power Beam Combination”Executive Summary
Section titled “Executive Summary”This research highlights the critical role of CVD diamond in next-generation high-average-power laser systems, specifically addressing the challenge of thermal management in beam combination architectures. Diamond’s unique physical properties enable system scalability previously unattainable with conventional materials.
- Core Application: Utilizing MPCVD diamond plates for beam combination concepts in very high average power laser systems (kW-class and above).
- Fundamental Challenge Solved: Diamond’s unparalleled thermal conductivity mitigates thermal lensing and wavefront distortion, which are primary limiting factors in high-power optics.
- Material Requirement: Requires ultra-high purity, low-loss Optical Grade Single Crystal Diamond (SCD) to minimize intrinsic absorption and prevent thermal runaway.
- Design Implication: The concept relies on precision machining and ultra-smooth polishing of the SCD component to ensure minimal scattering and high optical fidelity across the operating bandwidth.
- 6CCVD Advantage: We provide large-area, high-transmittance SCD wafers, customizable geometries, and industry-leading surface polishing (Ra < 1 nm) necessary for this demanding photonics application.
Technical Specifications
Section titled “Technical Specifications”The realization of high-power diamond-based optics depends on exploiting diamond’s fundamental material limits. The following table summarizes the critical material properties and geometric requirements for diamond components used in this beam combining application.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Required Material Grade | Optical Grade SCD | N/A | Essential for low absorption at common laser wavelengths (e.g., 1064 nm) |
| Thermal Conductivity (Bulk) | > 2000 | W/mK | Maximum thermal management capacity required to handle high average power |
| Component Dimensions | Custom (Prism/Plate) | mm/cm | 6CCVD offers plates up to 125 mm (PCD) and custom laser-cut sizes |
| Thickness (SCD Wafer) | 100 - 500 | µm | Optimized thickness for thermal transport and minimized absorption losses |
| Surface Roughness (Ra) | < 1 | nm | Required for minimizing scattering losses and high Laser-Induced Damage Threshold (LIDT) |
| Intrinsic Absorption (Alpha) | < 0.05 | cm-1 | Crucial for minimizing bulk heating and subsequent thermal lensing |
| Required Metalization | AR/HR Coatings | N/A | Custom Ti/Pt/Au or dielectric stacks for anti-reflection purposes |
Key Methodologies
Section titled “Key Methodologies”The high-power beam combination concept necessitates CVD diamond components grown and processed under stringent specifications. Replicating or extending this research requires expertise in high-purity MPCVD growth and advanced post-processing:
- High-Purity MPCVD Growth: Growth of Single Crystal Diamond (SCD) layers, typically on a proprietary diamond seed crystal, using the MPCVD process. Achieving extremely low nitrogen incorporation (< 1 ppm) is vital to ensure minimal absorption centers.
- Structural Integrity Control: Precise control of growth parameters (gas flow, pressure, temperature 800 °C - 1300 °C) to minimize strain and defects, ensuring optical uniformity across the finished plate.
- Defect Reduction Processing: Post-growth annealing (often at > 1800 °C, HPHT) or electron irradiation treatments to convert residual nitrogen impurities into optically benign states, maximizing transparency in the visible and infrared spectra.
- Precision Geometrical Machining: Using high-precision laser cutting or ablation techniques to achieve the specific prism, slab, or wedge geometries required for the beam combination scheme (e.g., specific angles for total internal reflection or interference).
- Ultra-Precision Surface Finishing (Polishing): Chemical-Mechanical Polishing (CMP) optimized for diamond surfaces to achieve roughness Ra < 1 nm. This step is non-negotiable for high-LIDT applications.
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”6CCVD is uniquely positioned to supply the advanced diamond materials and processing services required to manufacture next-generation, high-power beam combiners and thermal optics based on this diamond concept.
Applicable Materials
Section titled “Applicable Materials”To replicate and scale the thermal management capabilities described in this study, 6CCVD recommends:
- Optical Grade SCD: High-purity Single Crystal Diamond (SCD) optimized for transmission across common laser wavelengths (NIR, MIR). Available in thicknesses from 0.1 µm up to 500 µm.
- Large-Area PCD (For Non-Critical Areas): For larger, less optically demanding thermal spreaders or structural supports used in the laser housing, our high-quality Polycrystalline Diamond (PCD) substrates (up to 125mm in size) offer exceptional thermal sinking capabilities.
Customization Potential
Section titled “Customization Potential”The geometric requirements for beam combining (prisms, wedges, critical angles) necessitate bespoke manufacturing, a core strength of 6CCVD:
- Custom Dimensions and Shaping: We offer custom laser cutting and shaping services to produce the specific angled components or critical mounting dimensions required by the beam combiner architecture. Plates/wafers are available up to 125 mm (PCD).
- Advanced Polishing Services: We guarantee ultra-smooth SCD surfaces with roughness Ra < 1 nm, critical for minimizing scattering losses and maximizing the Laser-Induced Damage Threshold (LIDT) at high average powers.
- Integrated Metalization: 6CCVD provides in-house metalization services for electrodes or coating adhesion layers. We routinely deposit Au, Pt, Pd, Ti, W, and Cu, necessary for robust mounting, heat sinking, or preparation for specialized Anti-Reflection (AR) or High-Reflectivity (HR) dielectric coatings.
Engineering Support
Section titled “Engineering Support”Successfully integrating diamond into high-power laser systems is a nuanced process.
- 6CCVD’s in-house PhD engineering team specializes in material selection and processing specifications for demanding high-power photonics and thermal management projects.
- We assist clients in defining the optimal material grade (purity, thickness, surface finish) needed to achieve specified thermal stability and optical throughput for similar high-power beam combining systems.
- We offer global logistics support, providing reliable shipping (DDU default, DDP available) of custom diamond components directly to your research facility.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Researchers in Australia report a novel approach to laser brightness scaling based on beam combination in a diamond Raman amplifier. Efficient power transfer to a Stokes input is demonstrated using a three pump beam arrangement. An analysis is also presented revealing that the concept may be applicable to continuous beam generation at kilowatt power levels and orders-of-magnitude higher when using isotopically purified diamond at reduced temperature. (Picture: Aaron McKay et al., article number 1600130 in this issue, Image credit: Ondrej Kitzler)