Ultrafast high-power lasers are employed in a wide variety of applications in science and industry. Thin-disk oscillators can offer compelling performance for these applications. However, because of the high intracavity peak power, a large amount of self-phase modulation (SPM) is picked up in the intracavity air environment. Consequently, the highest performance oscillators have been operated in a vacuum environment. Here, we introduce a new concept to overcome this hurdle. We cancel the SPM picked up in air by introducing an intracavity phase-mismatched second-harmonic-generation crystal. The resulting cascaded ${\chi }^{(2)}$ processes provide a large SPM with a sign opposite the one originating from the air. This enables laser operation in air at 210 W average output power with 780 fs, 19 μJ pulses, the highest output power of any semiconductor saturable absorber mirror (SESAM) modelocked laser operated in air to date, to the best of our knowledge. This result paves the way to a novel approach for nonlinearity management in high-power lasers.

中文翻译：

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大功率超快薄盘激光振荡器中的自相位调制消除

超快高功率激光器广泛应用于科学和工业领域。薄盘振荡器可以为这些应用提供出色的性能。但是，由于腔内峰值功率高，因此在腔内空气环境中会拾取大量的自相位调制（SPM）。因此，性能最高的振荡器已在真空环境下工作。在这里，我们引入了一个新概念来克服这一障碍。我们通过引入腔内相位不匹配的第二谐波生成晶体来消除空气中拾取的SPM。结果级联${\chi }^{（\mathrm{2个}）}$流程提供了一个大型SPM，其符号与源自空气的符号相反。据我们所知，这使得激光器能够在780 fs，19μJ脉冲的情况下以210 W的平均输出功率在空气中运行，这是迄今为止在空气中运行的任何半导体可饱和吸收镜（SESAM）建模激光器中最高的输出功率。这一结果为大功率激光器非线性管理的新颖方法铺平了道路。