Tcypkin Anton N, Ponomareva Evgenia A, Putilin Sergey E, Smirnov Semen V, Shtumpf Sviatoslav A, Melnik Maksim V, E Yiwen, Kozlov Sergei A, Zhang Xi-Cheng
Opt Express. 2019 May 27;27(11):15485-15494. doi: 10.1364/OE.27.015485.
Polar liquids are strong absorbers of electromagnetic waves in the terahertz range, therefore, historically such liquids have not been considered as good candidates for terahertz sources. However, flowing liquid medium has explicit advantages, such as a higher damage threshold compared to solid-state sources and more efficient ionization process compared to gases. Here we report systematic study of efficient generation of terahertz radiation in flat liquid jets under sub-picosecond single-color optical excitation. We demonstrate how medium parameters such as molecular density, ionization energy and linear absorption contribute to the terahertz emission from the flat liquid jets. Our simulation and experimental measurements reveal that the terahertz energy has quasi-quadratic dependence on the optical excitation pulse energy. Moreover, the optimal pump pulse duration, which depends on the thickness of the jet is theoretically predicted and experimentally confirmed. The obtained optical-to-terahertz energy conversion efficiency is more than 0.05%. It is comparable to the commonly used optical rectification in most of electro-optical crystals and two-color air filamentation. These results, significantly advancing prior research, can be successfully applied to create a new alternative source of terahertz radiation.
极性液体是太赫兹波段电磁波的强吸收体，因此，从历史上看，这类液体一直未被视为太赫兹源的理想候选材料。然而，流动的液体介质具有明显的优势，比如与固态源相比具有更高的损伤阈值，与气体相比具有更高效的电离过程。在此，我们报告了在亚皮秒单频光激发下，对扁平液体射流中太赫兹辐射高效产生的系统研究。我们展示了诸如分子密度、电离能和线性吸收等介质参数如何对扁平液体射流的太赫兹发射产生影响。我们的模拟和实验测量表明，太赫兹能量与光激发脉冲能量呈准二次方依赖关系。此外，理论上预测并通过实验证实了取决于射流厚度的最佳泵浦脉冲持续时间。所获得的光到太赫兹的能量转换效率超过0.05%。这与大多数电光晶体中常用的光整流以及双色空气丝形成相当。这些结果显著推进了先前的研究，可成功应用于创建一种新的太赫兹辐射替代源。
