超强频率梳激光场驱动下多光子共振谐波辐射的相位突变研究

本文从理论上研究了在双色频率梳激光场驱动下多光子谐波辐射光谱中的相位突变现象。我们利用Floquet理论非微扰地模拟了频率梳激光场与原子分子等量子系统的相互作用过程。谐波辐射信号是多光子偶极跃迁相干叠加的结果,通过调节频率梳激光场间的相对相位,可以相干地控制谐波辐射信号的强度。通过对谐波信号进行傅里叶变换,可以提取不同跃迁路径的相对相位信息。我们通过改变频率梳组激光场的强度和频率组分实现多光子跃迁频率,让其跨越共振跃迁频率时,谐波相位会发生突变。从而可以观测超强激光场驱动下量子系统共振跃迁频率的斯塔克能移。

Phase jump in multiphoton resonant harmonic emission driven by strong frequency-comb fields

This paper presents a theoretical investigation of the phase jump of multiphoton harmonic emission driven by two frequency-comb fields.The Floquet theorem is employed to provide a nonperturbative and exact treatment of the interaction between a quantum system and frequency-comb fields.Multiple multiphoton-transition paths for the harmonic emission are coherently summed.The phase information about paths can be extracted via the Fourier Transform analysis of the harmonic signals which oscillate as a function of the relative phase between two frequency-comb fields.Phase jumps were observed when harmonic emission was sweeping across the resonance by varying the frequency or intensity of two frequency-comb fields,which allows us to observe the Stark-shifted transition energy of resonant frequency of quantum system driven by strong laser fields.