Abstract-Determination of Dielectric Function of Water in THz Region in Wood Cell Wall Result in an Accurate Prediction of Moisture Content

Han Wang, Tetsuya Inagaki, Ian D. Hartley,  Satoru Tsuchikawa, Matthew Reid

https://link.springer.com/article/10.1007/s10762-019-00594-0

This report follows up previous work that presented a model for the simultaneous detection of moisture content and density of wood using Terahertz time-domain spectroscopy. A significant improvement in the prediction accuracy of the model is demonstrated by including a moisture content-dependent dielectric function for the water within the wood samples. Justification for using the dielectric function is presented, the prediction accuracy is quantified, and the results compared with prior work.

Abstract-Subcycle Terahertz Nonlinear Optics

Xin Chai, Xavier Ropagnol, S. Mohsen Raeis-Zadeh, Matthew Reid, Safieddin Safavi-Naeini, and Tsuneyuki Ozaki

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.121.143901

The nonlinear interaction of subcycle electromagnetic radiation with matter is the current frontier in ultrafast nonlinear optics and high-field physics. Here, we investigate nonlinear optical effects induced by intense, subcycle terahertz radiation in a doped semiconductor. We observe a truncation of the half-cycle terahertz pulse and an emission of high-frequency terahertz photons. We attribute our observations to the abrupt current drop caused by strong intervalley scattering effects. By adding an extra half-cycle terahertz pulse with opposite polarity, we monitor the evolution of the nonlinear carrier dynamics during a quasi-single-cycle pulse. Our results demonstrate the differences between nonlinear effects for subcycle and multicycle terahertz pulses. It also suggests a new approach to subcycle control of terahertz waveforms, and the generation of high-order terahertz harmonics could be realized by using multicycle pulses.

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