Quasi-phase-matched generation of coherent extreme-ultraviolet light
Quasi-phase-matched generation of coherent extreme-ultraviolet light
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DOI：
10.1038/nature01222
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发表时间：
2003-01-02
期刊：
影响因子：
64.8
通讯作者：
Backus, S
中科院分区：
文献类型：
--
作者：
Paul, A;Bartels, RA;Backus, S
高次谐波发生是一种众所周知的产生相干极紫外 (EUV) 光的方法，光子能量高达约 0.5 keV（参考文献 1、2）。这是通过将飞秒激光聚焦到气体中并向前辐射基频激光频率的高次谐波来实现的(3,4)。然而，尽管该过程可以产生高能光子，但仅针对 50-100 eV 量级的光子能量证明了有效的高次谐波产生（参考文献 5）。气体电离阻止激光和 EUV 光以相同的速度传播，这严重限制了转换效率。在这里，我们报告了一种克服这个问题的技术，并演示了激光到 EUV 的准相位匹配频率转换。使用调制空心波导周期性地改变驱动转换的激光强度，即使在存在大量电离的情况下，我们也能有效地产生 EUV 光。调制光纤的使用将高次谐波光的能谱转变为比其他方式更高的光子能量。我们预计这项技术可以成为先进光刻和高分辨率成像应用的相干 EUV 源的基础。在未来的工作中，也有可能产生孤立的阿秒脉冲。
High-harmonic generation is a well-known method of producing coherent extreme-ultraviolet (EUV) light, with photon energies up to about 0.5 keV (refs 1, 2). This is achieved by focusing a femtosecond laser into a gas, and high harmonics of the fundamental laser frequency are radiated in the forward direction(3,4). However, although this process can generate high-energy photons, efficient high-harmonic generation has been demonstrated only for photon energies of the order 50-100 eV (ref. 5). Ionization of the gas prevents the laser and the EUV light from propagating at the same speed, which severely limits the conversion efficiency. Here we report a technique to overcome this problem, and demonstrate quasi-phase-matched frequency conversion of laser light into EUV. Using a modulated hollow-core waveguide to periodically vary the intensity of the laser light driving the conversion, we efficiently generate EUV light even in the presence of substantial ionization. The use of a modulated fibre shifts the energy spectrum of the high-harmonic light to significantly higher photon energies than would otherwise be possible. We expect that this technique could form the basis of coherent EUV sources for advanced lithography and high-resolution imaging applications. In future work, it might also be possible to generate isolated attosecond pulses.