为了研究金属纳米结构下高次谐波辐射的过程,通过数值求解薛定谔方程理论研 究了He+在蝴蝶型金属纳米结构下高次谐波辐射的特点。结果表明在蝴蝶型金属纳米结构下,谐波 辐射截止频率随He+空间位置远离纳米结构中心点而增大;当He+沿正(负)向远离纳米结构中心点 时,谐波截止频率主要由激光正(负)向部分产生。由于金属纳米结构的间隙尺寸有限,谐波辐射 在某一特定He+空间位置呈现最大截止频率。在双色场调控下,谐波光谱呈现一个333 eV的 超长平台区,通过叠加该平台区谐波可获得脉宽在25～28 as的超短远紫外脉冲。

In order to study the high-order harmonic emission process in metal nanostructure, the high-order harmonic generation from He+ in bowtie-shaped metal nanostructure is theoretically investigated by solving time-dependent Schrdinger equation. Results show that in bowtie-shaped metal nanostructure, the harmonic radiation cut-off frequency can be extended when the spatial position of He+ is away from the nanostructure gap center. The harmonic cut-off frequency is mainly generated by the positive (negative) parts of laser when He+ is moving away from the gap center of nanostructure along the positive (negative) directions. Due to the limited gap size of metal nanostructure, the maximum cutoff frequency can be found in some specific spatial position of He+. With the control of two-color field, the harmonic spectrum shows a 333 eV super-continuum platform region. By superimposing the harmonics of the platform region, ultrashort ultraviolet pulses with pulse widths ranging from 25 as to 28 as can be obtained.