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 | Commissariat Ă lâĂnergie Atomique et aux Ănergies Alternatives, UniversitĂ© de Bordeaux |
| Citations | 1 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis report details the development and performance of a 1 kHz Yb:YAG thin-disk regenerative amplifier designed for high-energy picosecond operation, aiming toward the 1 J-1 kW-1 ps class challenge.
- Core Achievement: The system demonstrated an amplified pulse energy of up to 50 mJ at a 1 kHz repetition rate, recompressed to 900 fs.
- Efficiency Benchmark: This performance yielded an 18% non-saturated optical-optical efficiency, cited as the best reported for a CW-pumped regenerative cavity utilizing a single Yb:YAG thin-disk head.
- Material System: The amplifier uses a 220 ”m thick, 7%-doped Yb:YAG thin-disk, CW diode-pumped at 969 nm and mounted on a diamond heat-sink.
- CW Baseline: In fundamental mode CW operation, the cavity delivered > 220 W of output power with a high beam quality factor (M2=1.08) and 35% optical-optical efficiency.
- Limiting Factor: The primary constraint on output power is thermal loading within the BBO Pockels cell. At only 50 W output power, the BBO crystal temperature rises beyond 40 °C.
- System Degradation: This thermal issue degrades the long-term voltage contrast ratio of the Pockels cell, leading to reduced beam quality and output power stability.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Gain Medium | Yb:YAG (7% doped) | N/A | Thin-disk material |
| Disk Thickness | 220 | ”m | Thin-disk dimension |
| Disk Diameter | 12 | mm | Thin-disk dimension |
| Pumping Wavelength | 969 | nm | CW Diode Pumping |
| Cavity Length | 4.8 | m | Linear regenerative cavity |
| Disk Curvature (Unpumped) | 4 | m | Radius of curvature |
| Fundamental Mode Diameter | 4.8 | mm | On the thin-disk |
| Mode Matching Percentage | 86 | % | Match to flat-top pump diameter |
| Repetition Rate | 1 | kHz | Regenerative operation frequency |
| Seeding Pulse Energy | 1.2 | mJ | Stretched input pulse |
| Seeding Pulse Duration | 1.4 | ns | Stretched input pulse |
| Seeding Spectral Bandwidth | 2.5 | nm | FWHM |
| CW Output Power | > 220 | W | Fundamental mode operation |
| CW Optical-Optical Efficiency | 35 | % | Fundamental mode operation |
| CW Beam Quality (M2) | 1.08 | N/A | Fundamental mode operation |
| Amplified Pulse Energy | Up to 50 | mJ | Regenerative operation |
| Regenerative Efficiency | 18 | % | Non-saturated optical-optical efficiency |
| Recompressed Pulse Duration | 900 | fs | Final output pulse length |
| BBO Crystal Dimensions | 12x12x40 | mm3 | Pockels cell aperture |
| BBO Operating Temperature | > 40 | °C | At 50 W output power (limiting factor) |
Key Methodologies
Section titled âKey MethodologiesâThe regenerative amplifier utilizes a simple, linear cavity design combined with high-power thin-disk technology to manage thermal load and achieve high average power.
- Gain Medium Configuration: A 220 ”m, 7%-doped Yb:YAG thin-disk is mounted on a diamond heat-sink for efficient thermal extraction.
- Pumping Scheme: The disk is continuously wave (CW) diode-pumped at 969 nm, providing the necessary gain for high-repetition-rate operation.
- Cavity Design: A 4.8 m long linear cavity is employed, incorporating a magnification telescope to optimize the mode size.
- Mode Matching: The fundamental cavity mode (4.8 mm diameter) is carefully matched to 86% of the flat-top pump diameter on the disk to maximize energy extraction efficiency.
- Seeding: The cavity is seeded with 1.2 mJ, 1.4 ns stretched pulses, ensuring the input signal is compatible with the regenerative amplification process.
- Pulse Selection/Switching: Regenerative operation at 1 kHz is achieved using a thin-film polarizer in combination with a large aperture BBO single crystal Pockels cell for high-speed switching.
- Thermal Management Challenge: Despite the use of a thin-disk, the BBO Pockels cell acts as the limiting component due to thermal absorption, requiring future engineering solutions to maintain stability and increase output energy beyond 50 mJ.
Commercial Applications
Section titled âCommercial ApplicationsâThe development of high-energy, high-repetition-rate picosecond lasers based on Yb:YAG thin-disk technology is critical for applications requiring high average power and precise energy delivery.
- Advanced Micromachining: Used for high-speed, high-precision ablation, drilling, and cutting of hard materials (e.g., ceramics, semiconductors) where minimal heat-affected zones are required.
- High-Energy Secondary Source Generation: Provides the necessary pump energy for driving high-flux X-ray sources, high-energy electron beams, or other particle accelerators used in research and industrial inspection.
- Plasma Physics and Fusion Research: Serves as a robust front-end or driver for large-scale laser facilities, enabling experiments in high-field physics and inertial confinement fusion studies.
- Industrial Manufacturing: Applicable in high-throughput manufacturing lines where 1 kW class average power is needed for rapid processing of components.
- Atmospheric Research: High-power, high-repetition-rate systems are essential for advanced LIDAR and remote sensing applications, as referenced by related work in the field.
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).