Abstract-Optimization for vertically scanning terahertz attenuated total reflection imaging

Hongxiang Liu, Yuye Wang, Degang Xu, Zhinan Jiang, Jining Li, Limin Wu, Chao Yan, Longhuang Tang, Yixin He, Dexian Yan, Xin Ding, Hua Feng, and Jianquan Yao

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-16-20744

Terahertz attenuated total reflection imaging has been used to develop preliminary applications without any in-depth analysis of the nature of present systems. Based on our proposed vertically scanning imaging system, an analysis of optimum prism design and polarization selection for error reduction is presented theoretically and experimentally, showing good agreement. By taking the secondary reflection inside the prism and the prism deflection into consideration, p-polarized terahertz waves are recommended for prisms with a base angle below 31°, leading to minimum error. This work will contribute to the development of more practical application of terahertz attenuated total reflection scanning imaging in various fields with enhanced performance.

© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Compact and stable high-repetition-rate terahertz generation based on an efficient coaxially pumped dual-wavelength laser

Yang Liu, Kai Zhong, Jialin Mei, Chu Liu, Jie Shi, Xin Ding, Degang Xu, Wei Shi, Jianquan Yao

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-25-31988

A compact and stable terahertz (THz) source is demonstrated based on difference frequency generation (DFG) pumped by an efficient dual-wavelength acousto-optic (AO) Q-switched solid-state Nd:YLF laser with composite gain media (a-cut and c-cut) in the coaxial pumping configuration. Optimal power ratio and pulse synchronization of the orthogonal polarized 1047/1053 nm dual-wavelength laser could be realized by varying the pump focusing depth and/or pump wavelength. The total power of 2.92 W was obtained at 5 kHz pumped by 10-W laser-diode power at 803 nm. Such an efficient dual-wavelength laser demonstrated good stability and inconspicuous timing jitter benefiting from the suppressed gain competition between two resonating wavelengths. An 8-mm-long GaSe crystal was employed to generate THz waves at 1.64 THz by DFG and the maximum THz average output power was about 0.93 μW. This compact coaxial pumping method can be extended to all kinds of neodymium (Nd) doped laser crystals to produce different dual-wavelength lasers for various THz wavelength generation, which have good prospects for portable and costless applications like imaging, non-destructive inspection, etc.

© 2017 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Active KTaO3 hybrid terahertz metamaterial

• Liang Wu, 
• Jinglong Liu, 
• Hui Li, 
• Chunfeng Ding, 
• Ningning Xu, 
• Xiaolei Zhao, 
• Zongcheng Xu, 
• Quan Sheng, 
• Jianquan Yao, 
• Jining Li, 
• Xin Ding & 
• Weili Zhang

https://www.nature.com/articles/s41598-017-05529-0

The dielectric properties of an active KTaO3 hybrid metamaterial structure and its tunability under external electric fields are investigated at room temperature by means of terahertz time-domain spectroscopy. Application of the electric field leads to an appreciable tuning of the dielectric loss, which is up to 17%. Meanwhile, the refractive index also changes appreciably. These findings are attributed to the internal space charge field in the crystal caused by the excited free carriers.

Abstract-Broadband and wide-angle RCS reduction using a 2-bit coding ultrathin metasurface at terahertz frequencies

• Lanju Liang
• , Minggui Wei
• , Xin Yan
• , Dequan Wei
• , Dachuan Liang
• , Jiaguang Han
• , Xin Ding
• , GaoYa Zhang
•  & Jianquan Yao

http://www.nature.com/articles/srep39252

A novel broadband and wide-angle 2-bit coding metasurface for radar cross section (RCS) reduction is proposed and characterized at terahertz (THz) frequencies. The ultrathin metasurface is composed of four digital elements based on a metallic double cross line structure. The reflection phase difference of neighboring elements is approximately 90° over a broadband THz frequency. The mechanism of RCS reduction is achieved by optimizing the coding element sequences, which redirects the electromagnetic energies to all directions in broad frequencies. An RCS reduction of less than −10 dB bandwidth from 0.7 THz to 1.3 THz is achieved in the experimental and numerical simulations. The simulation results also show that broadband RCS reduction can be achieved at an incident angle below 60° for TE and TM polarizations under flat and curve coding metasurfaces. These results open a new approach to flexibly control THz waves and may offer widespread applications for novel THz devices.

Abstract-Broadband, wide-angle, low-scattering terahertz wave by a flexible 2-bit coding metasurface

Xin Yan, Lanju Liang, Jing Yang, Weiwei Liu, Xin Ding, Degang Xu, Yating Zhang, Tiejun Cui, and Jianquan Yao
https://www.osapublishing.org/oe/abstract.cfm?uri=oe-23-22-29128

Abstract: Expanding bandwidths and arbitrary control of technology remain key issues in the field of electromagnetic waves, especially in terahertz (THz) wave. In this paper, we propose a novel method to achieve broadband low-scattering THz characteristics with wide-angle and polarization independence by a 2-bit flexible and nonabsorptive coding metasurface. The coding metasurface is composed of four digital elements based on double cross metallic line for “00”, “01”, “10”, and “11.” The reflection phase difference of neighboring elements is about 90° over a broad THz frequency band and wide incident angles. The low scattering coefficients below –10 dB were achieved over a wide frequency band from 0.8 THz to 1.5 THz when the incident angle is less than 50° by coding the four elements sequences. This superior property is maintained when the flexible coding metasurface is wrapped around a metallic cylinder with different dimensions. These results present a novel method to control THz waves freely and demonstrate significant scientific value in practical applications.

© 2015 Optical Society of America

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