We study the generation of terahertz (THz) radiation from a dual-color filament in air for a Ti:sapphire pump and with different wavelengths of the seed pulse using the unidirectional pulse propagation equation (UPPE). The local transient photocurrent model indicates that the most efficient THz generation corresponds to the seed with either halved or doubled pump frequency compared with the other seed frequencies studied. However, UPPE simulations reveal the crucial decrease in the effective interaction area of the pump and the seed pulses in the case of lower-frequency seeds, due to the strong diffraction of the seed radiation on the plasma obstacle formed by the pump pulse. As the result, the energy of THz radiation drops from 260 nJ for the double frequency to 7 nJ for the halved one.

我们使用单向脉冲传播方程（UPPE）研究了用于Ti：蓝宝石泵的空气中双色灯丝产生的太赫兹（THz）辐射，并具有不同波长的种子脉冲。局部瞬态光电流模型表明，与研究的其他种子频率相比，最有效的THz生成对应于泵频率减半或成倍的种子。但是，UPPE模拟表明，在低频种子的情况下，由于种子辐射在由泵浦脉冲形成的等离子障碍物上的强烈衍射，因此泵浦和种子脉冲的有效相互作用区域显着减小。结果，太赫兹辐射的能量从两倍频率的260 nJ下降到一半频率的7 nJ。