三色圆偏振激光组合脉冲驱动氦原子产生椭圆偏振的阿秒脉冲

我们提出利用频率为ω,3ω和强度较弱的2ω组成的三色圆偏振激光组合脉冲驱动氦原子能够得到椭偏率较大的阿秒脉冲链的一种方法.通过强场近似方法,计算了氦原子在两色和三色圆偏振激光组合脉冲驱动下发射高次谐波谱及其合成阿秒脉冲链,比较了氦原子(初态为s态)在这两种情况下发射高次谐波谱的特点及其合成阿秒脉冲链椭偏率的大小,结果发现,在反旋的两色ω,3ω激光脉冲基础上加入了频率为2ω的第三色激光脉冲联合作用到氦原子上,所得到的阿秒脉冲链的椭偏率相对于双圆场情况下有所增加,通过调整ω,3ω激光的强度比,并且选择适当的第三色激光的强度,对初态为s态的原子,仍能够得到具有较大椭偏率的阿秒脉冲链.

Generation of elliptically polarized attosecond pulse trains of He atom driven by tri-circular laser pulses

We present a method to obtain a large elliptical attosecond pulse train of He atom driven by a trichromatic circular polarization laser pulse composed of the counterrotating circularly polarized laser pulse with frequencies , and frequency with a weak intensity. We calculate the high-order harmonic spectra emitted by helium atoms driven by two-color and three-color circularly polarized laser pulses and the synthesized attosecond pulse train by using the strong field approximation method. It is found that the ellipticity of the attosecond pulse train emitted He atom driven by the two-color laser pulse joined the third color laser pulse with a low intensity can be enhanced, compared with the case of two-color laser pulse. A big ellipticity for attosecond pulse train can be obtained for atom whose initial state is s state by adjusting the intensity ratio of laser pulses with the appropriate intensity of the third color laser with frequency .