Real-time observation and control of the high-harmonics generation and coulomb explosion of metal clusters in intense laser fields

本研究旨在揭示强激光场中团簇多重电离和高次谐波产生的波包动力学过程，并基于量子光学原理对这些过程进行控制。首先，我们成功地观察到了金属-稀有气体或金属-双原子分子团簇激发态表面的波包运动。观测到的波包运动给出了激发态表面的形状。我们已经研究了控制相关波包运动的可能性，并发现锁相光脉冲对对于该目的是有效的。我们已经成功地进行了这种情况下，通过控制在一个单一的集群与阿秒的精度产生的两个核波包的干扰。接下来，我们构建了电子飞行时间探测器（e-TOF），旨在观察当相关波包暴露于拍瓦激光场时喷射的电子和离子。我们已经测量了原子和分子的光电子光谱，把在拍瓦激光场使用该e-TOF和第一次发现，除了低能量的化合价成分低于50 eV的许多团体观察到的200 eV左右的高能量成分。这种高能电子喷射预计是软X射线区域中高次谐波产生的对应物。目前，我们正试图通过拍瓦激光脉冲的相位调制来控制这种高能电子喷射。该技术有望在不久的将来实现阿秒软X射线脉冲源。

This research has been carried out in order to reveal the wave-packet dynamics associated with the multiple ionization and high harmonics generation of clusters in intense laser fields and to control those processes based on the quantum optical philosophy. First we succeeded in observing the wave-packet motion on the excited-state surface of the metal-rare gas or the metal-diatomic molecule clusters. The observed wave-packet motion has given the shape of the excited-state surface. We have examined the possibility of controlling the relevant wave-packet motion and found that a phase-locked optical-pulse pair is effective for that purpose. We have successfully carried out this scenario by controlling the interference of two nuclear wave packets generated in a single cluster with an accuracy of attoseconds. Next we constructed the electron time of flight detector (e-TOF) aiming at observing the electrons and ions that are ejected when the relevant wave packet is exposed to petawatt laser fields. We have measured the photoelectron spectra of atoms and molecules put in the petawatt laser fields using that e-TOF and found for the first time a high-energy component around 200 eV in addition to the low-energy valence component below 50 eV observed by many groups so far. This high-energy electron ejection is expected to be a counterpart of the high-harmonics generation in the soft X-ray region. At the moment we are trying to control this high-energy electron ejection through the phase modulation of the petawatt laser pulse. This technique is expected to realize the attosecond soft X-ray pulse source in the near future.