Faculty of Physics and International Laser Center of M.V. Lomonosov Moscow State University, Moscow, Russia.
Nat Commun. 2013;4:1936. doi: 10.1038/ncomms2923.
The advent of X-ray lasers allowed the realization of compact coherent soft X-ray sources, thus opening the way to a wide range of applications. Here we report the observation of unexpected concentric rings in the far-field beam profile at the output of a two-stage plasma-based X-ray laser, which can be considered as the first manifestation of a mirage phenomenon in X-rays. We have developed a method of solving the Maxwell-Bloch equations for this problem, and find that the experimentally observed phenomenon is due to the emergence of X-ray mirages in the plasma amplifier, appearing as phase-matched coherent virtual point sources. The obtained results bring a new insight into the physical nature of amplification of X-ray radiation in laser-induced plasma amplifiers and open additional opportunities for X-ray plasma diagnostics and extreme ultraviolet lithography.
X 射线激光的出现使得紧凑相干软 X 射线源得以实现，从而为广泛的应用开辟了道路。在这里，我们报告了在两级基于等离子体的 X 射线激光输出的远场光束轮廓中观察到意想不到的同心环，这可以被认为是 X 射线中海市蜃楼现象的首次表现。我们已经为这个问题开发了一种求解麦克斯韦-布洛赫方程的方法，并发现实验中观察到的现象是由于等离子体放大器中出现了 X 射线海市蜃楼，表现为相位匹配的相干虚拟点源。所得到的结果为激光诱导等离子体放大器中 X 射线辐射放大的物理性质带来了新的认识，并为 X 射线等离子体诊断和极紫外光刻开辟了更多的机会。
