碟片再生放大器实现110 mJ、2.1 ps、1 kHz重复频率激光输出

Thin-Disk Regenerative Amplifier with 110 mJ,2.1 ps,and 1 kHz Repetition Rate Laser Output

为实现高重复频率、百毫焦、高光束质量皮秒激光的输出,基于激光谐振腔设计方法,设计了Yb∶YAG双碟片再生放大器。采用啁啾脉冲放大技术路线,实现了重复频率为1 kHz、单脉冲能量为110 mJ、脉冲宽度为2.1 ps、光束质量因子M^(2)<1.1、波长为1030.2 nm的激光输出。脉冲压缩前单脉冲能量为124.2 mJ,>1 h的平均输出功率稳定性均方根值为0.56%@120 W。研究结果对于大能量高重复频率碟片激光器的发展有着重要意义。

Objective Thin-disk structures have excellent thermal conductivity and small thermal aspheric aberration. Therefore, thin-disk lasers have excellent power and energy scalability and simultaneously ensure good beam quality. Thin-disk regenerative amplifiers can achieve a magnification of 105-108 in a single stage, making them ideal sources for small-signal amplification. Currently, the maximum energy and highest average power of the thin-disk regenerative amplifier are 300 mJ and 1.9 kW, as reported by the Max Bonn Institute and TRUMPF Company of Germany in 2016 and 2019, respectively. Compared with foreign countries, there is a large gap in single-pulse energy and average power in China.Methods A chirped pulse amplification technology route including pulse broadening, energy amplification, and pulse compression is used. A seed laser is generated using an all-fiber mode-locked oscillator and an amplifier, and an appropriate pulse repetition frequency is generated using a frequency selector. The regenerative amplifier is designed based on the laser resonant cavity design method, and it possesses a Yb∶YAG dual thin-disk ring cavity structure. The pulse compressor consists of two reflective gratings for pulse width compression.Results and Discussions The maximum average output power of the regenerative amplifier(with uncompressed pulses) is 124.2 W, with a slope efficiency of 27.4% and an optical-to-optical conversion efficiency of 11.4%. The root-mean-square(RMS)value of the power stability at an average power of 120.4 W is 0.56% and the peak-to-valley(PV) proportion is 4.3%, indicating good power stability. The compressed pulse energy is 110 mJ, the measured center wavelength is 1030.2 nm, and the spectral bandwidth is 1.26 nm. The actual measured pulse width is 2.10 ps, and the measured beam quality, denoted M^(2), is less than 1.1, indicating that the amplifier has beam transmission capacity close to the diffraction limit.Conclusions This study designs a dual thin-disk regenerative amplifier and achieves a long-term stable laser output with a maximum power of 124.2 W, pulse width of 580 ps, and repetition rate of 1 kHz before pulse compression. Using a reflective grating compressor, the pulse width is compressed to 2.1 ps, the single pulse energy is 110 mJ, and the beam quality M^(2) is <1.1. The next step in this work is to use this laser as a seed source and conduct research on Joule-level high-energy thin-disk multi-pass amplifiers.