Abstract-A study of plant growth regulators detection based on terahertz time-domain spectroscopy and density functional theory

 

Xiaoxue Du, Yafei Wang, Xiaodong Zhang, Guoxin Ma, Yong Liu, Bin Wang,  Hanping Mao

https://pubs.rsc.org/en/content/articlelanding/2021/ra/d1ra05222e

Terahertz technology is receiving increasing attention for its use as an efficient non-destructive, non-contact and label-free optical method for qualitative and quantitative detection. The aim of this study was to develop a chemical analysis methodology based on terahertz time-domain spectra that could be used to detect plant growth regulators, such as glyphosine, naphthaleneacetic acid, daminozide and gibberellic acid. The THz fingerprint spectra of these four PGRs were located in the 0.3–1.8 THz, with the peaks of glyphosine at 0.32, 0.49, 0.74, 0.87, 0.96, and 1.49 THz; daminozide at 0.33, 0.39, 0.55, 0.67, and 1.17 THz; gibberellic acid at 0.46, 0.58, 0.92, and 1.38 THz and naphthaleneacetic acid at 0.43, 0.57, 0.73, and 0.90 THz. The results showed that these four plant growth regulators exhibited numerous distinct spectral features in frequency-dependent absorption spectra, which demonstrated the qualitative capacity of terahertz time-domain. The origin of the observed terahertz absorption peaks of these four plant growth regulators was determined through density functional theory calculations and analysis of absorption spectra. Discriminant analysis method was used to evaluate the classification trends of the four plant growth regulators based on their THz absorbance spectra. Generally, this study provides a reference for the rapid detection of plant growth regulators in fruits and vegetables by using terahertz spectroscopy technology.

Abstract-Terahertz Devices with EMXT Structure Fabricated by MEMS

Shengjie Yang, Hongda Lu, Zhipeng Liu, Yong Liu,  Bin Li , Xin Lv

https://ieeexplore.ieee.org/document/8563681

Due to the micro-dimension of terahertz devices and antennas, it requires more stringent processing technology. Micro-Electro-Mechanical Systems (MEMS) used to fabricate terahertz functional devices and antennas is a good choice for the high accuracy, good consistence and low cost. In this paper, one approach to obtain antennas and passive devices in terahertz band is proposed, which based on electromagnetic crystal structure and MEMS technology. The band-pass filter, 90° bend waveguide and H-plane horn antenna operating at terahertz band are presented as examples. All of them have good agreement between simulation and measurement.

Abstract-Active multifunctional terahertz modulator based on plasmonic metasurface

Jie Ji, Siyan Zhou, Weijun Wang, Chunya Luo, Yong Liu, Furi Ling, and Jianquan Yao

Fig. 1 (a) The schematic of an efficient light modulator based on a frequency-selective tunable terahertz metasurface. The sample size was 15 mm*15mm. (b) the OM image of the sample when the photo-resist was lift off. (c) Geometry of the unit-cell of the metasurface with parameters: L1 = 120 um, L2 = 80 um, h1 = 30 um, h2 = 25 um, a = 30 um, g = w = 5um. Metal thickness for the metasurface: d = 100 nm (5 nm Ti + 95 nm Al).

https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-27-3-2363&id=404331

An active multifunctional terahertz modulator based on plasmon-induced transparency (PIT) metasurface under the effect of external infrared light was investigated theoretically and experimentally. A distinct transparency window, which resulted from the near-field coupling between two resonators, could be observed in the transmission spectra. Experimental results showed a phenomenon infrared light induced blue shift on the both resonator with increasing optical powers. When the optical power was tuned from 0 mW to 400 mW, the amplitude tunability of transmission at transparency window reached to 34.01%, much larger than that at the two resonance frequencies. Moreover, the phase tunability of the transmission at 0.98 THz reached to 31.35%. Meanwhile, the amplitude variation was limited to 10%. Furthermore, a coupled Lorentz oscillator model was adopted to analyze the near-field interaction of the resonances. Experimental results were in good agreement with the analytical fitting results.

© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Experimental Realization of Terahertz Waveguide-Fed Circularly Polarized Double-Fan-Shaped Slot Antenna

Pengfei Zhao ;  Yong Liu ;  Hongda Lu ;  Yuming Wu ;  Xin Lv

http://ieeexplore.ieee.org/document/7904601/

A terahertz (THz) waveguide-fed circularly polarized double-fan-shaped slot antenna (DFSSA) based on a silicon micromachining technology is proposed. The antenna is fed by a WR1.9 waveguide. Optimized rotation angle of the double-fan-shaped slot can realize left-hand circular polarization or right-hand circular polarization. The measured axial ratios are lower than 1.5 dB from 490 to 500 GHz. The proposed DFSSA is suitable to be used as feeders in the THz imaging and detection systems.