European XFEL GmbH, Albert-Einstein-Ring 19, D-22761 Hamburg, Germany.
Elettra-Sincrotrone Trieste, Basovizza I-34149, Italy.
Nat Commun. 2014 Apr 16;5:3648. doi: 10.1038/ncomms4648.
Ultrafast extreme ultraviolet and X-ray free-electron lasers are set to revolutionize many domains such as bio-photonics and materials science, in a manner similar to optical lasers over the past two decades. Although their number will grow steadily over the coming decade, their complete characterization remains an elusive goal. This represents a significant barrier to their wider adoption and hence to the full realization of their potential in modern photon sciences. Although a great deal of progress has been made on temporal characterization and wavefront measurements at ultrahigh extreme ultraviolet and X-ray intensities, only few, if any progress on accurately measuring other key parameters such as the state of polarization has emerged. Here we show that by combining ultra-short extreme ultraviolet free electron laser pulses from FERMI with near-infrared laser pulses, we can accurately measure the polarization state of a free electron laser beam in an elegant, non-invasive and straightforward manner using circular dichroism.
超快极紫外和 X 射线自由电子激光有望在生物光子学和材料科学等领域引发变革，其作用类似于过去二十年来的光学激光。尽管在未来十年内，它们的数量将稳步增长，但对它们进行全面表征仍然是一个难以实现的目标。这是它们更广泛采用的一个重大障碍，因此也是充分实现它们在现代光子科学中的潜力的一个重大障碍。尽管在超高极紫外和 X 射线强度下的时间特性和波前测量方面已经取得了很大进展，但在准确测量其他关键参数（如偏振状态）方面，如果有任何进展的话，也非常有限。在这里，我们展示了通过将 FERMI 的超短极紫外自由电子激光脉冲与近红外激光脉冲相结合，我们可以使用圆二色性以优雅、非侵入和直接的方式准确测量自由电子激光束的偏振状态。
