Abstract-Terahertz Spectral of Enantiomers and Racemic Amino Acids by Time-Domain-Spectroscopy Technology

Yan Liu, Tao Zhou, Jun-Cheng Cao,


https://www.sciencedirect.com/science/article/pii/S1350449518307102

The absorption spectra of four amino acids were studied. These spectra are obtained by terahertz time-domain spectroscopy (TDS) technique. The four amino acids are alanine, methionine, leucine, and valine, respectively. The spectra of their enantiomers (L-, D-) and racemic compounds (DL-) were investigated. Although the two isomers have very similar structures, their absorption spectra are obviously different. The absorption coefficient of each structure is calculated by the density functional theory (DFT), and the simulated spectra of each structure are obtained. It is shown that the number of the calculated peaks is in good agreement with the experimental ones. The experimental spectra were compared with the theoretical spectra. The differences between the absorption spectra of isomers are presented, and the reasons for the differences were analyzed. The vibratory spectra of biomolecules were studied, and the correlation between molecular structure and function was further understood.

Abstract-6.2-GHz modulated terahertz light detection using fast terahertz quantum well photodetectors

Hua Li, Wen-Jian Wan, Zhi-Yong Tan, Zhang-Long Fu, Hai-Xia Wang, Tao Zhou, Zi-Ping Li, Chang Wang, Xu-Guang Guo, Jun-Cheng Cao

(Submitted on 9 May 2017)

https://arxiv.org/abs/1705.03182

The fast detection of terahertz radiation is of great importance for various applications such as fast imaging, high speed communications, and spectroscopy. Most commercial products capable of sensitively responding the terahertz radiation are thermal detectors, i.e., pyroelectric sensors and bolometers. This class of terahertz detectors is normally characterized by low modulation frequency (dozens or hundreds of Hz). Here we demonstrate the first fast semiconductor-based terahertz quantum well photodetectors by carefully designing the device structure and microwave transmission line for high frequency signal extraction. Modulation response bandwidth of gigahertz level is obtained. As an example, the 6.2-GHz modulated terahertz light emitted from a Fabry-P\'{e}rot terahertz quantum cascade laser is successfully detected using the fast terahertz quantum well photodetector. In addition to the fast terahertz detection, the technique presented in this work can also facilitate the frequency stability or phase noise characterizations for terahertz quantum cascade lasers.