1 kHz Yb -YAG thin-disk high-energy picosecond regenerative amplifier
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2022-01-01 |
| Journal | EPJ Web of Conferences |
| Authors | Marie-Christine Nadeau, Ph. Balcou, Dominique Descamps, Christophe FĂ©ral, Vincent Fortin |
| Institutions | Université de Bordeaux, Centre National de la Recherche Scientifique |
| Citations | 1 |
| Analysis | Full AI Review Included |
Technical Documentation: Diamond Heat Sinks for 1 kHz High-Energy Picosecond Regenerative Amplifiers
Section titled âTechnical Documentation: Diamond Heat Sinks for 1 kHz High-Energy Picosecond Regenerative AmplifiersâThis analysis addresses the critical role of Single Crystal Diamond (SCD) in managing extreme thermal loads within Yb:YAG thin-disk laser systems, based on the research detailing a high-energy picosecond regenerative amplifier operating at 1 kHz.
Executive Summary
Section titled âExecutive SummaryâThe reported research demonstrates a high-performance thin-disk regenerative amplifier reliant on advanced thermal management provided by a diamond heat sink.
- Record Performance: Achieved 50 mJ amplified pulse energy at 1 kHz repetition rate, representing the highest performance reported for a CW-pumped regenerative cavity using a single Yb:YAG thin-disk head.
- High Efficiency: Demonstrated high optical-optical efficiencies: 35% in CW mode (220 W output) and 18% in regenerative operation.
- Thermal Foundation: The high-power density pumping is enabled by mounting the 220-”m thick Yb:YAG disk onto a diamond heat-sink, leveraging diamondâs superior thermal conductivity (k > 2000 W/mK).
- Beam Quality: Maintained near diffraction-limited beam quality in CW operation (M2=1.08).
- Limitation Identified: Output power is currently limited by thermal issues in peripheral optical components (specifically the BBO Pockels cell), which experience temperature increases beyond 40 °C, degrading voltage contrast ratio and stability.
- Future Improvement: The success of the diamond-mounted Yb:YAG disk suggests that integrating CVD diamond into other thermally stressed optical components (such as Pockels cells or frequency conversion crystals) is key to further power scaling.
Technical Specifications
Section titled âTechnical SpecificationsâKey operational parameters and performance metrics extracted from the study, highlighting the demands placed on the diamond heat sink.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Gain Medium Heat Sink | Diamond | N/A | Essential component for thermal management |
| Yb:YAG Disk Thickness | 220 | ”m | Extremely thin active material layer |
| Yb:YAG Disk Diameter | 12 | mm | Standard thin-disk size |
| CW Pump Wavelength | 969 | nm | Diode pumping source |
| Maximum CW Output Power | > 220 | W | Achieved in fundamental mode |
| Maximum Pulse Energy | 50 | mJ | Amplified regenerative output |
| Repetition Rate | 1 | kHz | System operational frequency |
| Beam Quality Factor | 1.08 | M2 | Near diffraction-limited performance (CW) |
| CW Optical-Optical Efficiency | 35 | % | High efficiency achieved using diamond cooling |
| Pockels Cell Thermal Limit | > 40 | °C | BBO crystal temperature increase at 50 W output |
| Compressed Pulse Duration | 900 | fs | Final laser output |
Key Methodologies
Section titled âKey MethodologiesâThe high-power performance is contingent upon a specific configuration, emphasizing the role of the CVD diamond material in thermal stabilization.
- Gain Medium Preparation: A 220-”m thick Yb:YAG disk (7% doping, 12 mm diameter) was used as the active material.
- Interface Bonding: The Yb:YAG thin-disk was mounted directly onto a Single Crystal Diamond (SCD) heat-sink to enable efficient and rapid heat dissipation.
- Cavity Setup: Established a 4.8 m long linear regenerative cavity.
- Pump Scheme: Used CW diode pumping at 969 nm.
- Mode Matching: A magnification telescope was employed to match the 4.8 mm fundamental mode diameter to 86% of the flat-top pump diameter on the disk surface.
- Switching Mechanism: Regeneration was controlled via a combination of a thin-film polarizer and a large aperture BBO single crystal Pockels cell (12x12x40 mm3) operating at 1 kHz.
6CCVD Solutions & Capabilities: Enabling High-Power Laser Stability
Section titled â6CCVD Solutions & Capabilities: Enabling High-Power Laser StabilityâThis application relies entirely on diamondâs ability to handle high heat flux. 6CCVD provides the necessary ultra-high purity MPCVD diamond substrates required to replicate and significantly scale this research, particularly addressing secondary thermal issues (Pockels cell degradation).
Applicable Materials
Section titled âApplicable MaterialsâTo replicate the demonstrated heat management, 6CCVD recommends:
- Optical Grade Single Crystal Diamond (SCD): Required for thin-disk mounting. Our SCD offers superior purity and thermal conductivity (> 2000 W/mK) necessary for minimizing temperature gradients across the Yb:YAG interface, ensuring stable operation and high beam quality.
- High-Purity Polycrystalline Diamond (PCD): Suitable for large-area heat spreaders or supporting structures where the SCD crystal size is a limiting factor, potentially providing a cost-effective platform for future scaled systems (up to 125 mm wafers).
- Boron-Doped Diamond (BDD): Highly relevant for future addressing of the Pockels cell thermal limitations. BDD can be engineered as thermally robust, highly conductive electrodes or resistive heaters for precise temperature control or integrated heat removal near the BBO crystal.
Customization Potential
Section titled âCustomization Potentialâ6CCVDâs in-house capabilities meet and exceed the material specifications required for next-generation high-energy amplifiers:
| Capability | Specification | Relevance to Research |
|---|---|---|
| Custom Dimensions | Plates/wafers up to 125 mm (PCD), Substrates up to 10 mm thick. | Allows for scaling beyond the 12 mm Yb:YAG disk used in the study. |
| SCD Thickness Control | 0.1 ”m to 500 ”m (SCD) | Provides flexibility for various heat spreading or optical window applications. |
| Surface Finish | Ra < 1 nm (SCD) | Critical for achieving maximal thermal contact conductance (minimal air gaps) between the Yb:YAG and the diamond heat sink. |
| Custom Metalization | Au, Pt, Pd, Ti, W, Cu (Internal capability). | Allows for direct, customized application of robust contact layers for bonding the Yb:YAG disk or for creating integrated electrodes/sensors on SCD/BDD elements. |
| Precision Shaping | High-precision laser cutting and grinding services. | Enables custom shaping of the SCD heat sink to fit complex cavity designs and cooling manifolds. |
Engineering Support
Section titled âEngineering Supportâ6CCVDâs commitment extends beyond material supply. We offer specialized support for resolving complex high-power issues:
- Thermal Modeling Expertise: Our in-house PhD team can assist engineers with thermal finite element analysis (FEA) to optimize material thickness, mounting geometry, and cooling interfaces for high-power laser systems.
- Interface Optimization: We provide consultation on achieving optimal diamond-to-crystal bonding to maximize heat flux and preserve the beam quality factor (M2) at increasing pump powers.
- Mitigating Secondary Thermals: We can assist in designing BDD solutions or custom diamond cooling components to manage heat in secondary systems (e.g., Pockels cells), thereby increasing the long-term voltage contrast stability and output energy ceiling of the regenerative amplifier.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
1J-1kW-1ps is a real scientific and technological challenge involving thermal, energy and short pulse management.Yb:YAG is nowadays the best-suited amplifier material to address these challenges.Recently, 1.1 J at 1 kHz has been reported with cryogenic-cooled thick Yb:YAG disks but at a longer pulse duration of 4.5 ps [1].On the other hand, shorter pulses of 920 fs have been obtained by the solely thin-disk technology with an energy of 720 mJ at 1 kHz [2].In the frame of laser development (HORIZON) for new high energy secondary sources and plasma physics, CELIA has chosen an alternative way combining thin-disk technology to provide a high energy front-end and rotating water-cooled disk technology for the final power amplifier.Although the best performances of Yb:YAG thin-disk regenerative amplifiers reach 200 mJ at 1-5 kHz [2,3], most of the published schemes are rather complex and may leave key issues unreported.Here, we report on the development of the Yb:YAG thin-disk front-end based on a simple scheme with the experimental results and the faced issues.The regenerative cavity is based on a 220-”m 7%-doped Yb:YAG thin-disk CW diode-pumped at 969 nm.The 12 mm disk is mounted on a diamond heat-sink and it has a 4 m radius of curvature when not pumped.The thindisk is placed at one end of a 4.8 m long linear cavity.A magnification telescope is inserted in such a way that the fundamental mode has a 4.8 mm diameter on the disk matching 86% of the flat-top pump diameter.The regenerative operation is insured by a thin-film polarizer combined with a large aperture BBO single crystal (12x12x40 mm 3 ) operating at 1 kHz.The cavity is seeded by 1.2 mJ-1.4 ns stretched pulses with a 2.5 nm spectral bandwidth (FWHM).