三色激光控制量子路径生成短于30阿秒的孤立脉冲

采用多周期的800 nm钛宝石激光组合1600 nm中红外脉 冲辐照氦离子产生高次谐波发射功率谱. 相对于单色场情形, 谐波谱出现明显的双平台结构, 且在第二平台区出现了光滑的连续辐射谱, 其转化效率相对于第一平台低了约两个数量级. 通过附加脉宽为1 fs的27次谐波脉冲到双色激光场的特定时域, 可以控制电子电离在半个光学周期内迅速提升, 获得了由单一短量子路径贡献的连续辐射谱, 使得第二平台区谐波的转化效率相对于组合场情形增强4个数量级, 且连续谱的频谱范围从第二平台区扩展到第一平台区, 叠加该连续谱190次到285次谐波生成了脉宽为29 as的强、短孤立脉冲.

Isolated intense sub-30-as pulse generation by quantum path control in the three-color laser pulse

We theoretically investigate the high-order harmonic generation from He⁺in the two-color laser pulse, which is composed of a multi-cycle 800 nm laser and 1600 nm laser. Compared with the case of the fundamental laser, the harmonic spectrum presents a two-plateau structure, and a broadband supercontinuum appears in the second plateau, of which the efficiency is approximately 2 orders of magnitude lower than that of the first plateau. Adding the 27th harmonic pulse to the two-color laser at a proper time, we can control the ionization mostly occurring at half the optical cycle, and the short quantum path can be picked out, the second plateau is heightened four orders of magnitude compared with the case of the two-color case. Furthermore, the supercontinuum spectrum is extended from the second plateau to the first one. An intense isolated pulse with a duration of 29 as is obtained by superposing the 190th---285th harmonics in the continuous region.