中文摘要：

报告由不同脉冲宽度（半高宽,FWHM）和不同载波-包络相位（CEP,Φ）的激光产生的高次谐波辐射能量输出时间特性即发射特性的研究结果.计算表明,由宽度为几个周期的激光产生的高次谐波辐射的截止能量明显低于由无限长脉冲宽度激光产生的截止能量ωmax=3.17Up＋Ip（其中ωmax为光子角频率,Up和Ip分别为激光有质动力势和原子的电离能）.例如,由两周期（FWHM）,Φ=15°的激光产生的高次谐波辐射的截止能量为ωmax=2.90Up＋Ip,此时发射特性单脉冲（即分布单脉冲）具有最大的能量带宽0.86Up.脉冲中心位置的载波相位和时间宽度分别为0.94rad（弧度）和1.29rad.而该激光脉冲在Φ=-75°时能产生截止能量为ωmax=2.70Up＋Ip,最大能量带宽为0.70Up的双分布脉冲,其中心位置分别为-0.58rad和2.43rad,宽度分别为1.22rad和1.33rad.随着激光脉冲宽度的增加,分布单脉冲的能量带宽比时间宽度下降得更快.对于一定宽度的激光脉冲,所产生的分布单脉冲的能量带宽和时间宽度的CEP依赖性显示出180°的周期结构.利用这个有趣的特点,在实验上可以通过调节CEP来选择分布脉冲的能量参数,也可用来定位和控制阿秒脉冲的时间参数.理论分析指出,只要选择合适的阿秒X射线能量带宽,CEP不稳定性对于光电子谱和测量结果的影响将大为降低,甚至在最大程度上消除这种影响.这些研究结果不仅有助于在物理上深入了解高次谐波辐射的动力学过程,而且对于进一步在实验上优化和选择阿秒单脉冲和双脉冲具有重要的参考和指导意义.

英文摘要：

Reported are the emission properties （energy-time distributions） of high-order harmonic generation （HHG） calculated for lasers of different pulse durations （ τL, in units of radian） in full width at half maximum （FWFIM） and different carrier-envelope phases （CEPs, Φ）. Calculations demonstrate that the cutoff energy of HHG spectrum produced by a few-cycle laser is less than thatby an infinite duration laser （hwmax = 3.17Up ＋ Ip, where ω max is the angular frequency of the photon, Up the ponderomotive potential of the laser field, and Ip the atomic ionization potential）. A τL = 4π rad, Φ = 15° laser can produce a single distribution pulse peaked at 0.94 rad and spanning 1.29 rad with a cutoff energy hw max = 2.90Up ＋ Ip and a bandwidth 0.86 Up. For the same laser but with Φ = - 75°, double distribution pulses occur with equal amplitudes, cutoff energy hwmax = 2.70 Up ＋ Ip and bandwidth 0.70 Up. These two pulses are peaked at - 0.58 rad and 2.43 rad,span 1.22 rad and 1.33 rad, respectively. Calculations also demonstrate that the bandwidth of a selected distribution pulse decreases much faster than its duration as the laser duration grows. The CEP dependence of the single distribution pulse parameters （its energy and time positions） show interesting 180° periodic structures. These features enable us to select attosecond pulse parameters and temporally control them by adjusting CEP. Theoretical analysis shows that the influences of CEP instability on the measured photoelectron spectra and the experimental results may be weakened to the maximum extent or even eliminated by choosing appropriate energy bandwidths of X-rays in attosecond measurements. All these results are helpful in realizing the HHG dynamic process. They can be used as new references in optimizing and selecting single and double attosecond pulses.