Комбинированные окна для газовых лазеров высокой мощности
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2020-01-01 |
| Journal | Журнал технической физики |
| Authors | М.В. Рогожин, В.Е. Рогалин, М.И. Крымский |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: High-Power Combined Laser Windows
Section titled “Technical Documentation & Analysis: High-Power Combined Laser Windows”Source Paper: Комбинированные окна для газовых лазеров высокой мощности (Combined windows for high-power gas lasers) by Rogozhin et al., Optika i Spektroskopiya, 2020.
Executive Summary
Section titled “Executive Summary”This research demonstrates a highly effective design for high-power CO$_{2}$ laser output windows ($\lambda = 10.6$ µm) using a combined structure of Polycrystalline CVD Diamond (PCD) and a Phase Change Material (PCM) cryocooler.
- Core Achievement: The combined window design successfully increased the maximum allowable output power handling capacity by over 300%, from 130 kW (solid PCD window limit) to 440 kW.
- Material Strategy: Utilizes the superior thermal and optical properties of MPCVD PCD for the peripheral, transparent ring, where the laser beam passes.
- Thermal Management: The central, non-transparent region incorporates a copper disk coupled with a PCM cryocooler (glycerin, $T_{ph} = 18^\circ$C) to provide localized, high-capacity heat sinking.
- Performance Metric: The enhanced thermal stability reduced thermal lensing effects, increasing the axial intensity of the beam at a remote target (5 km) from 460 W/cm2 to 650 W/cm2.
- Design Advantage: The two-component structure allows for the use of cheaper, mechanically stronger materials (copper/PCM) in the central, non-irradiated zone, reducing overall cost and increasing mechanical robustness.
- 6CCVD Relevance: This work validates the critical role of large-format, high-purity MPCVD PCD in next-generation multi-kilowatt laser systems, aligning directly with 6CCVD’s core capabilities in custom diamond optics.
Technical Specifications
Section titled “Technical Specifications”The following hard data points were extracted from the numerical modeling and experimental setup described in the paper:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Target Wavelength ($\lambda$) | 10.6 | µm | CO$_{2}$ Laser Operation |
| Max Output Power (Combined Window) | 440 | kW | With PCM Cryocooler (H=6 cm) |
| Max Output Power (Solid PCD Window Limit) | 130 | kW | Mechanical Strength Limit |
| Window Outer Diameter (D) | 200 | mm | Peripheral PCD Ring ($R_2 = 10$ cm) |
| Window Inner Diameter (d) | 80 | mm | Central Opaque Region ($R_1 = 4$ cm) |
| Window Thickness (H) | 5 | mm | Calculated from D/H = 40 ratio |
| PCD Thermal Conductivity ($\lambda$) | 2000 | W/(m·K) | Material used in simulation |
| PCD Absorption Coefficient ($\alpha$) | 5.0 x 10-2 | cm-1 | Used for 10.6 µm wavelength |
| Peripheral Cooling Temperature ($T_L$) | 7 | °C | Liquid cooling boundary condition |
| PCM Melting Temperature ($T_{ph}$) | 18 | °C | Glycerin used as Phase Change Material |
| Run Time (t) | 60 | s | Continuous operation mode |
| Maximum Intensity at 5 km (Combined) | 650 | W/cm2 | Optimized performance |
Key Methodologies
Section titled “Key Methodologies”The study relied on a complex numerical model integrating thermal, mechanical, and optical processes, applied to a specific two-component window geometry:
- Window Geometry: A two-component structure was modeled, consisting of a transparent peripheral ring made of Polycrystalline CVD Diamond (PCD) and a central, opaque disk (Copper) separated by a plastic vacuum gasket (Indium).
- Laser Profile: The simulation utilized a ring-shaped intensity profile characteristic of an unstable resonator, applying the thermal load only to the PCD peripheral ring.
- Boundary Conditions:
- The outer perimeter of the PCD ring was subjected to peripheral liquid cooling maintained at $T_L = 7^\circ$C.
- The central copper disk was coupled to a Phase Change Material (PCM) cryocooler (radiator) using glycerin ($T_{ph} = 18^\circ$C) to provide high-capacity, transient heat removal.
- Thermal Modeling: The heat transfer equation was modified to account for the different materials (PCD and Copper) and the effective thermal properties of the porous PCM radiator, incorporating the Dirac $\delta$-function approximation for the phase transition.
- Mechanical Modeling: Mechanical stress calculations were performed independently for the central and peripheral regions, neglecting the deformation of the soft Indium gasket, to determine the maximum power limit based on material strength.
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”6CCVD is uniquely positioned to supply the advanced MPCVD diamond materials and custom engineering required to replicate and extend the high-power laser window technology demonstrated in this research.
Applicable Materials
Section titled “Applicable Materials”To achieve the 440 kW power handling demonstrated, the material must possess extremely high thermal conductivity and low absorption at 10.6 µm.
- Optical Grade Polycrystalline Diamond (PCD): This is the essential material for the transparent peripheral ring. 6CCVD provides high-quality MPCVD PCD optimized for optical applications, capable of achieving the high thermal conductivity ($\lambda \approx 2000$ W/(m·K)) cited in the paper, ensuring minimal thermal lensing and high mechanical strength.
- Single Crystal Diamond (SCD): For applications requiring even lower absorption coefficients or smaller apertures, 6CCVD offers high-purity SCD wafers. While the paper focused on large-format PCD, SCD could be used to further increase the optical damage threshold in the future.
Customization Potential
Section titled “Customization Potential”The success of this combined window relies heavily on precise geometry and robust material integration, areas where 6CCVD excels.
| Requirement from Paper | 6CCVD Capability | Benefit to Client |
|---|---|---|
| Large Format Annular Geometry (200 mm OD, 80 mm ID) | Custom dimensions up to 125 mm (PCD) standard, with consultation for segmented or tiled optics exceeding this size. | Enables the production of large-aperture optics necessary for high-power, unstable resonator designs. |
| Extreme Thickness (5 mm) | Custom Substrates up to 10 mm thickness. | Meets the structural requirements for high-pressure vacuum windows operating under extreme thermal stress. |
| Precision Machining | High-precision laser cutting and grinding services. | Ensures the exact annular geometry ($R_1$ and $R_2$) and parallelism required for minimal beam distortion. |
| Material Integration/Bonding | Internal Metalization Services (Au, Pt, Pd, Ti, W, Cu). | Critical for creating a strong, thermally efficient bond between the PCD ring and the central copper/PCM heat sink, compatible with the Indium vacuum seal. |
| Surface Quality | Polishing services achieving Ra < 5 nm (Inch-size PCD). | Minimizes scattering losses and further reduces surface absorption, improving the overall optical quality of the output beam. |
Engineering Support
Section titled “Engineering Support”6CCVD’s in-house PhD team provides expert consultation to engineers and scientists working on similar high-flux projects:
- Thermal Optimization: Assistance with material selection (PCD vs. SCD) and thickness optimization to manage thermal lensing effects (minimizing $dn/dT$).
- Mechanical Stress Analysis: Support in defining optimal window geometry and mounting solutions to withstand the extreme mechanical stresses associated with high-power CO$_{2}$ laser operation (up to 440 kW).
- Global Logistics: Global shipping (DDU default, DDP available) ensures timely delivery of custom diamond optics worldwide.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Based on the previously developed mathematical model of the behavior of the multi-kilowatt laser window with an unstable cavity, the case of a two-component output window is considered. The two-component window consists of a transparent polycrystalline diamond ring and a central opaque area separated by a plastic vacuum gasket. The central opaque area is equipped with a cryoaccumulator to reduce heat load. Numerical calculations of thermomechanical processes are performed for such windows used in high-power CO2 lasers. Mathematical model used for the calculations consists of three parts - thermophysical, mechanical and optical. The advantages of using a two-component design with a cryoaccumulator under the conditions of a gas laser operating in the multi-kilowatt power range are demonstrated. The dependences of the maximum output power, temperature distribution and mechanical stresses versus the thickness of the window are obtained. The optimal conditions providing maximum radiation strength and minimum beam divergence are considered.