Powerful ultrashort pulses in the deep-ultraviolet (deep-UV) are beneficial for diverse applications from fundamental science to industrial materials processing. However, reaching high powers via conventional approaches is challenging due to three central issues: dispersion, multiphoton absorption, and optical damage. Here, we simultaneously overcome these issues with a novel fifth-harmonic generation architecture optimized for group velocity matching. We use tilted pulse fronts, including a noncollinear geometry in the final sum-frequency generation stage. This enables lower intensities and longer crystals, thereby favoring the birefringently phase matched ${\chi ^{(2)}}$ process over higher-order multiphoton absorption processes. Moreover, we demonstrate low-loss cascaded ${\chi ^{(2)}}$-based spatiotemporal flattening of the input pulses, which enhances the uniformity of the conversion efficiency throughout the beam profile. Through these techniques, we realize a picosecond deep-UV generation source at 206 nm with record-high 2.5 W average output power and a repetition rate of 100 kHz. This result paves the way for a new era of high-power ultrafast deep-UV lasers.

中文翻译：

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通过组速度匹配的频率转换获得大功率皮秒深紫外光源

深紫外线（deep-UV）中强大的超短脉冲有益于从基础科学到工业材料加工的各种应用。然而，由于三个主要问题，通过常规方法达到高功率是具有挑战性的：色散，多光子吸收和光学损伤。在这里，我们通过针对组速度匹配进行了优化的新型第五谐波生成架构同时克服了这些问题。在最终的和频生成阶段，我们使用倾斜的脉冲前沿，包括非共线几何形状。这使得较低的强度和更长的晶体成为可能，从而与高阶多光子吸收过程相比，有利于双折射相匹配的$ {\ chi ^ {（2）}} $过程。此外，我们展示了低损耗的级联$ {\ chi ^ {（2）}} $基于输入脉冲的时空平坦化，这增强了整个光束轮廓的转换效率的均匀性。通过这些技术，我们实现了206 nm的皮秒深紫外线产生源，具有创纪录的2.5 W平均输出功率和100 kHz的重复频率。这一结果为大功率超快深紫外激光器的新时代铺平了道路。