量子路径控制生成宽频软X射线连续辐射谱

数值研究了双色激光脉冲与一维氩原子相互作用的谐波发射功率谱.双色激光脉冲由800 nm和1600 nm的两束激光组成，脉冲持续时间为9.7 fs.计算结果表明，相对相位为π时，谐波截止频率从单色场情形的58 eV大幅度地展宽到316 eV，获得频宽为93 eV的软X射线连续辐射谱.此外，还采用短程的普薛耳－特勒势和长程的软化库仑势进行比对，数值结果表明该连续辐射谱的存在具有普适性.通过半经典的“三步”模型和时频分析小波变换方法对该连续辐射谱进行分析，发现其主要由单一的“短”量子路径生成，直接叠加频率从22 关键词： 红外双色激光脉冲 连续辐射谱 阿秒脉冲

Generation of a broadband soft X-ray supercontinuum by quantum path control

We theoretically investigate the high-order harmonic generation (HHG) power spectra from a one-dimensional argon model atom irradiated by an infrared two-color laser beam, which are composed of 9.7 fs/800 nm laser pulses and 9.7 fs/1600 nm laser pulses. It is found that, when the relative phase equals π, the harmonic cutoff is dramatically widened from 58 eV to 316 eV compared with the case with the single color laser beam. It is also demonstrated that an ultrabroad soft-X-ray harmonic supercontinuum with a bandwidth of 93 eV can be obtained by adopting the soft-core potential and the Pschl-Tell potential calculations. In terms of the time-frequency analysis and the semiclassical three-step model, we also demonstrate that the ultrabroad harmonic supercontinuum is mainly generated from the short path. By superposing a series of properly selected harmonics, an isolated attosecond pulse with duration of 46 as is obtained. Compared with other schemes of generating single as pulses by quantum path control in two-color laser pulse, the10 fs/800 nm pulse used in our scheme enables easier manipulations in practical experimental implementations.