Abstract-Strong Terahertz Radiation from a Liquid-Water Line

Liang-Liang Zhang, Wei-Min Wang, Tong Wu, Shi-Jia Feng, Kai Kang, Cun-Lin Zhang, Yan Zhang, Yu-Tong Li, Zheng-Ming Sheng, and Xi-Cheng Zhang

https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.12.014005

Terahertz radiation generation from liquid water has long been considered impossible due to strong absorption. A few very recent works reported terahertz generation from water, but the mechanism is not clear and the efficiency demands to be enhanced. We show experimentally that strong single-cycle terahertz radiation with field strength of $0.2\mathrm{MV}{\mathrm{cm}}^{-1}$ is generated from a water line (or column) of approximately $200\mu m$ in diameter irradiated by a mJ femtosecond laser beam. This strength is 100-fold higher than that produced from air using single-color pumping. We attribute the mechanism to the laser-ponderomotive-force-induced current with the symmetry broken around the water-column interface. This mechanism can explain our following observations: the radiation can be generated only when the laser propagation axis deviates from the column center; the deviation determines its field strength and polarity; it is always $p$ polarized no matter whether the laser is $p$ or $s$ polarized. This study provides a simple and efficient scheme of table-top terahertz sources based on liquid water.

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Abstract-An Improved Ultrawideband Open-Short De-Embedding Method Applied up to 220 GHz

Yunqiu Wu,  Ya’nan Hao, Jun Liu,  Chenxi Zhao,  Yuehang Xu, Wenyan Yin, Kai Kang,

https://ieeexplore.ieee.org/document/8123503/

This paper presents an improved ultrawideband open-short de-embedding methodology. In contrast to the conventional measurement-based open-short de-embedding method, the presented method is a measurement-calculation hybrid method. First, the open and short de-embedding structures are measured, and the corresponding scattering parameters are obtained. Based on this, lumped-parameter models of the open and short de-embedding structures are established. Then, the established models are modified to solve the over de-embedding problem. Finally, the modified de-embedding structure models are implemented in the scattering parameters of device test structures to achieve ultrawideband de-embedding. To verify the proposed de-embedding method, the method is applied to active devices. The results before and after de-embedding are compared under multiple bias conditions. Furthermore, the results after de-embedding based on the conventional open-short method and the proposed method are compared up to 220 GHz. These results show that using the proposed method can achieve accurate ultrawideband de-embedding up to the terahertz frequency band.