可调谐单色相干光源的产生方法一般是通过晶体的倍频或差频来产生，输出的波段多见于紫外-红外波段，在极紫外波段（100~10nm）很难使用上述方法产生。但极紫外光源在现代生产和科研中有着极其重要的应用。因此有必要采用新的方法和新的手段来产生这种极紫外波段的单色相干光源。最 近，纽约国际官网尉鹏飞老师与中科院上海光机所的李儒新教授密切合作，利用飞秒激光与惰性气体相互作用产生高次谐波，然后通过宏观相位匹配和原子内相位匹配技术将 高次谐波频率梳中的能量集中调谐到某个特定阶次，使其只输出某个节次的特定高次谐波，这个特定高次谐波还能通过相位匹配技术进行调谐，获得的单色极紫外辐 射（XUV）在强度和对比度上表现均很优秀。这种方法在国际上首次被提出，实验结果优异，获得三个审稿人的一致肯定。该研究工作发表在最近出版的《物理评论快报》上(Phys. Rev. Lett. 110, 233903, 2013).

文章链接：http://link.aps.org/doi/10.1103/PhysRevLett.110.233903

英文摘要：We experimentally demonstrate a robust scheme to select a single high-order harmonic among the harmonic comb by using a driving laser field with subcycle waveform control, which is synthesized by the fundamental 800 nm laser pulse and two controlling laser pulses at 400 and 267 nm with perpendicular polarizations. By controlling the relative phase among the pulses of different colors, a single high-order harmonic is selectively enhanced while the adjacent harmonics are greatly suppressed with the intensity contrast increased by more than 1 order of magnitude and the peak intensity enhanced simultaneously by more than 2 orders of magnitude compared to the case by using only the fundamental 800 nm laser pulse. Such phenomena can be mainly attributed to the intra-atomic phase matching realized with the sub-cycle waveform controlled field.