Lasers with high average and high peak power as well as ultrashort pulse width have been all along demanded by nonlinear optics studies, strong-field experiments, electron dynamics investigations, and ultrafast spectroscopy. While the routinely used titanium-doped sapphire (Ti:sapphire) laser faces a bottleneck in the average power upscaling, ytterbium (Yb)-doped lasers have remarkable advantages in achieving high average power. However, there is still a substantial gap of pulse width and peak power between the Ti:sapphire and Yb-doped lasers. Here we demonstrate a high-power $\mathrm{Yb}\text{:}{\mathrm{CaAlGdO}}_4$ (Yb:CALGO) regenerative amplifier system, delivering 1040 nm pulses with 11 W average power, 50 fs pulse width, and 3.7 GW peak power at a repetition rate of 43 kHz, which to some extent bridges the gap between the Ti:sapphire and Yb lasers. An ultrabroadband Yb-doped fiber oscillator, specially designed spectral shapers, and Yb:CALGO gain medium with broad emission bandwidth, together with a double-end pumping scheme enable an amplified bandwidth of 19 nm and 95 fs output pulse width. To the best of our knowledge, this is the first demonstration of sub-100 fs regenerative amplifier based on Yb-doped bulk medium without nonlinear spectral broadening. The amplified pulse is further compressed to 50 fs via cascaded-quadratic compression with a simple setup, producing 3.7 GW peak power, which boosts the record of peak power from Yb:CALGO regenerative amplifiers by 1 order. As a proof of concept, pumped by the high-power, 50 fs pulses, 7.5–11.5 µm mid-infrared (MIR) generation via intrapulse difference-frequency generation is performed, without the necessity of nonlinear fiber compressors. It leads to a simple and robust apparatus, and it would find good usefulness in MIR spectroscopic applications.

中文翻译：

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多千兆瓦 50 fs Yb:CALGO 再生放大器系统，具有 11 W 平均功率和中红外生成

非线性光学研究、强场实验、电子动力学研究和超快光谱一直需要具有高平均和高峰值功率以及超短脉冲宽度的激光器。常规使用的掺钛蓝宝石 (Ti:sapphire) 激光器在平均功率提升方面面临瓶颈，而掺镱 (Yb) 激光器在实现高平均功率方面具有显着优势。然而，钛：蓝宝石和掺镱激光器之间的脉冲宽度和峰值功率仍有很大差距。在这里，我们展示了一个高功率$镝\text{：}{\mathrm{氧化钙}}_4$(Yb:CALGO) 再生放大器系统，以 43 kHz 的重复频率提供 1040 nm 脉冲，平均功率为 11 W，脉冲宽度为 50 fs，峰值功率为 3.7 GW，这在一定程度上弥合了 Ti:sapphire 和镱激光器。超宽带掺镱光纤振荡器、专门设计的光谱整形器和具有宽发射带宽的 Yb:CALGO 增益介质，以及双端泵浦方案，可实现 19 nm 的放大带宽和 95 fs 输出脉冲宽度。据我们所知，这是基于 Yb 掺杂体介质且无非线性光谱展宽的亚 100 fs 再生放大器的首次演示。放大的脉冲通过简单设置的级联二次压缩进一步压缩到 50 fs，产生 3.7 GW 的峰值功率，从而提高了 Yb 的峰值功率记录：CALGO 再生放大器 1 阶。作为概念证明，由高功率 50 fs 脉冲泵浦，通过脉冲内差频生成产生 7.5–11.5 µm 中红外 (MIR)，无需非线性光纤压缩器。它导致了一种简单而坚固的设备，并且在 MIR 光谱应用中会有很好的用处。