为了测量中红外激光相位及获得阿秒脉冲, 采用高次谐波截止能量随激光相位改变而变化的方法, 进行了中红外激光相位测量及阿秒脉冲输出的研究。引入一束少周期激光场后, 组合场相位对谐波发射截止能量的影响要比单独中红外激光场相位对谐波截止能量的影响明显很多。因此, 提出了一种利用谐波截止能量与相位角的对应关系测量多周期中红外激光相位的方法。同时理论研究了3束中红外激光场下发射高次谐波及阿秒脉冲的特点。结果表明, 适当调节3束激光场的延迟时间和相位角, 不仅谐波发射的截止能量得到了延伸, 而且单一的量子路径也被选择出来对谐波发射起作用, 形成了一个272eV的平台区; 通过叠加谐波谱上的谐波, 可获得一系列脉宽为34as的X射线光源。该研究对中红外激光相位测量及阿秒脉冲的输出是有帮助的。

In order to measure the phase of mid-infrared field and to obtain the attosecond pulse, the investigation on mid-infrared field phase measurement and attosecond pulse generation has been presented by using the relationship between phase and harmonic cutoff energy. With the introduction of a few-cycle pulse to mid-infrared field, the effect of phase of the combined field on harmonic cutoff energy became much more distinct in comparison with the single field. One new method of phase measurement was gotten. Further, harmonic extension spectra and attosecond pulse generation of the three-color mid-infrared field were numerically investigated. The results show that by properly adjusting the delay times and phases of three pulses, not only harmonic cutoff energy is extended, but also single quantum path is selected to contribute to the harmonic generation, resulting in supercontinuum with bandwidth of 272eV. Finally, by superposing the properly selected harmonics in supercontinuum region, a series of X-ray pulses with pulsewidth of 34as can be obtained. The investigation is helpful for phase measurement of mid-infrared field and attosecond pulse generation.