氦原子在双色强激光驱动下产生的太赫兹波辐射

Terahertz wave radiation of helium atom driven by intense two-color laser fields

基于量子力学的数值求解二维含时薛定谔方程的方法,研究了双色激光场驱动氦原子辐射太赫兹波的特点.研究结果表明,两束激光的相位差对太赫兹波的产额具有显著的调制作用,在高强度激光驱动下,当相位差分别为-0.5π和0.55π时,太赫兹波有最大产额,与光电流模型得到的结论一致.比较光电流模型和量子力学结果表明,在高强度激光驱动下,原子实的库仑场对形成电流的自由电子影响较小;同时,通过调节双色场的相位差,能够从氦原子发射的宽频太赫兹波得到时域空间脉宽在30飞秒以下的半周期波形.

We investigate the characteristics of terahertz wave radiation for a model helium atom driven by the two - color laser field, based on the numerical solution of two - dimensional time - dependent Schrtidinger equation in quantum mechanics. Our results show that the phase difference of the two - color laser pulses has signifi- cant effect on the strength of the terahertz wave. Under the intense laser driver, terahertz waves have the stronger yields when the phase differences are - 0.5 π and 0.55 π, which is consistent with the results of photocurrent model. Compared the results of photocurrent model with that of quantum mechanics calculation, it shows that the Coulomb force of the atomic core has small influence on the currents formed by the free electrons for helium atom driven by intense laser pulse. Meanwhile, by adjusting the phase difference of the two - color laser pulse, we can obtain a waveform of half - cycle within 30 femtosecond pulse width in time domain based on emission tera- hertz spectra of helium atom in intense two - color laser pulses.