提出了一种通过共线型双等离子体的简单方法实现双色场作用下辐射太赫兹波的频谱调制。利用修正的光电流模型, 模拟了共线型双等离子体在双色场条件下辐射太赫兹波的频谱分布。通过调节体系的参数, 研究了两等离子体间距及激光光强对太赫兹波频谱调制的影响。结果表明, 太赫兹频谱分布与两等离子体间距及双色激光强度有关。等离子体间距影响太赫兹波频谱的峰值个数和频移; 激光光强虽会影响单个等离子体辐射太赫兹波的峰值频率, 但是对于调制的频谱而言只会改变峰值的幅值。

A simple method to modulate the spectrum of the terahertz waves generated by two-color femtosecond pulses has been proposed, in which the terahertz waves generated from two collinear plasmas interfere each other. With a modified photocurrent model, the spectrum of the output terahertz wave has been simulated. By changing the time intervals between two plasmas and the pump power of femtosecond pulse, the modulated spectrum of terahertz can be observed. The results show that the number of peaks and frequency-shift of the terahertz spectrums are only depended on the time intervals between two plasmas; the power of pump laser makes great contributions to the frequency-shift of the terahertz wave generated by a single plasma, but for the whole output terahertz spectrum, it only affects the modulation amplitude not the frequency-shift.