Center for Ultrafast Optical Science, University of Michigan, 2200 Bonisteel Boulevard, Ann Arbor, Michigan 48109, USA.
Opt Lett. 2010 Oct 1;35(19):3186-8. doi: 10.1364/OL.35.003186.
Harmonics up to the 18th order are generated from solid targets by focusing 2 mJ, 50 fs pulses at 800 nm to a spot size of 1.7 μm (FWHM). To our knowledge, this is the first demonstration of high-harmonic generation with a very short focal length paraboloid (f/1.4) and kilohertz laser system. The harmonics have a low divergence (<4°) compared to the driving beam and conversion efficiencies (>10(-7) per harmonic) comparable to gas harmonics. No contrast enhancement techniques are employed, and the system is capable of operating at 500 Hz.
从固体目标产生的 18 阶谐波是通过将 2mJ、50fs 的 800nm 脉冲聚焦到 1.7μm 的光斑尺寸（FWHM）来实现的。据我们所知，这是首次使用非常短焦距抛物面镜（f/1.4）和千赫兹激光系统进行高次谐波产生的演示。与驱动光束相比，谐波的发散角较低（<4°），转换效率（每个谐波>10(-7)）与气体谐波相当。没有采用对比度增强技术，该系统能够以 500Hz 的频率运行。
