摘要:
通过数值求解一维含时薛定谔方程,本文研究了具有特定波长的双色激光脉冲与氦原子相互作用产生的高次谐波和阿秒脉冲,这里双色激光脉冲由5 fs较低强度基频钛宝石主脉冲与另一束较高强度的1330 nm红外附加脉冲构成.研究发现,若两束脉冲之间的相对相位选择合适,可以获得宽带连续辐射的高次谐波谱,叠加该连续辐射谱可获得脉宽为38 as的孤立短脉冲.进一步研究发现,不同于以往孤立阿秒脉冲研究中选出长、短量子路径之一作为辐射源,这里单阿秒脉冲来源于长、短两个量子路径的贡献,只是这两个量子路径在很宽的谐波次数变化范围内辐射时刻比较集中.
Abstract:
We have investigated theoretically the high-order harmonics and attosecond pulse generation by numerically solving the one-dimensional time-dependent Schr¨odinger equation from a helium atom in a two-color laser field, which is synthesized by adding a 1330-nm infrared pulse with higher intensity to an 800-nm fundamental pulse with lower intensity. Our results clearly show that if the phase difference between the two pulses is selected suitably, the generation of high-order harmonics spectrum with a broadband supercontinuum characteristic can be achieved, and an isolated 38 as pulse can be realized. By the time-frequency analysis, we find that the isolated attosecond pulse comes from the contribution of the long and short quantum paths, and for these two quantum paths the change of emission time with the harmonics order is rather slow. This is different from the traditional isolated attosecond pulse generation that a single quantum path needs to be picked up to obtain an isolated attosecond pulse.
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