Generation ofintense harmonics in the water window bytwo-color field and its applications

这三年的研究成果总结如下：(1)在双色场作用下，在10级以下，谐波显著增强，截止范围明显延长。水窗口(4.4~2.3 nm)内的谐波仅由基场证实。(2)通过控制两场之间的相对相位，使上下分支明显分开。用含时薛定谔方程计算的原子偶极矩解释了这一结果。(3)A 5-f。研制了载波包络相位稳定的全波型光学参量啁啾脉冲放大(OPCPA)系统，用于在水窗口产生高次谐波。OPCPA获得的最短脉冲宽度为5.5fs，最大平均功率为2.5W。(4)研制了一台超高分辨率激光光电子能谱仪。150μEV的分辨率是有史以来获得的最高分辨率。利用该系统对各种超导材料进行了研究。在不久的将来，利用新研制的OPCPA系统的双色场将在水窗内实现几十阿秒的脉冲。

The achievements for these 3 years are summarized as follows.(1) The significant enhancement of harmonics and the extension of cut off were observed below 10 run by two Color field. The harmonics in the water window (4. 4〜2. 3 nm) were confirmed by the fundamental field alone.(2) By controlling the relative phase between two fields, the lower and upper branches were clearly separated. The results were explained by the calculated atomic dipole moment from time-dependent Schrodinger equation.(3) A 5-fs. TW-class, carrier-envelope-phase-stabilized optical parametric chirped-pulse amplification (OPCPA) system was developed to generate intense harmonics in the water window. The pulse width of 5. 5 fs was the shortest and the average power of 2. 5 W at 1 kHz was the highest ever obtained by OPCPA(4) An ultra-high resolution laser-photoelectron spectrometer was developed. The resolution of 150 μeV is the highest ever obtained. The various superconductor materials were investigated by using this system. In the near future, a few tens of attosecond pulses will be realized in the water window by two-color field of a newly developed OPCPA system.