Abstract-Super terahertz phase shifter achieving high transmission and large modulation depth

Shuai Li, Jing Wang, Hao Tian, Li Li, Jianlong Liu, Guan Chao Wang, Jiaojiao Gao, Chengpeng Hu, and Zhongxiang Zhou

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-45-10-2834

We propose an industrial-grade liquid-crystal-based terahertz (THz) 2π-phase shifter with predictable ultra-high amplitude transmittance. The phase retardation reaches 360.5° at 1.68 THz by analyzing the birefringence of liquid crystal (LC), and the amplitude transmittance in 0.3–1.5 THz is over 83%. More than 91.5% transmittance can be reached by decreasing the scattering of the THz wave in the dynamic deflection process of LC molecules, and that is close to the transmittance limit of quartz-based devices. This millimeter-thick phase shifter reaches full phase modulation and ultra-high transmittance in a broad THz band, is easy to be integrated in a quasi-optical system with a compact size and can be utilized as a wave plate, even an element in a THz phased array.

© 2020 Optical Society of America

Abstract-Imidazolium-grafted graphene oxide via free radical polymerization: An efficient and simple method for an interpenetrating polymer network as electrolyte membrane

Amina Ouadah, 

Tianwei Luo, 

Jing Wang, 

Shuitao Gao, 

Xing Wang, 

Xin Zhang, 

Zhou Fang, 

Zeyu Wu, 

Jie Wang, 

Changjin Zhu, 

https://www.sciencedirect.com/science/article/pii/S0266353817327422

In this work, graphene oxide (GO) is modified via free radical polymerization with butylvinylimidazolium (b-VIB) to produce GO/IM, which is characterized using FTIR spectral analysis, X-ray diffraction (XRD), thermogravimetric analysis (TGA), Raman analysis, X-ray photoelectron spectroscopy (XPS), elemental analysis, and a morphology study with transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Further, GO/IM is incorporated for an in-situ polymerization, with the synthesized copolymer para-methyl styrene/butylvinylimidazolium (PMS/b-VIB) and synthesized poly(4,4′-diphenyl ether-5,5′-bibenzimidazole) (DPEBI) as a matrix, giving nanocomposite membranes referred to as GO/IM-X. These nanohybrid membranes possess higher conductivity than the pristine membrane of PMS/b-VIB/DPEBI and the conductivity increases with increasing amount of GO/IM, reaching 78.5 mS cm⁻¹ at 100 °C and 26.5 mS cm⁻¹ 25 °C (chloride conductivity), enhancements of about 14.93% and 33.16% compared to the pristine membrane. Nanocomposite membrane properties were investigated; the swelling ratio and water uptake, ion exchange capacity (IEC), thermal properties via TGA, structure characterization using FTIR, morphology via TEM and mechanical properties. Taken together, these results suggest the present nanohybrid membranes have great potential for use as polymer electrolyte membranes with fuel cell applications.

Abstract-Tunable terahertz wave difference frequency generation in a graphene/AlGaAs surface plasmon waveguide

Tao Chen, Liangling Wang, Lijuan Chen, Jing Wang, Haikun Zhang, and Wei Xia

https://www.osapublishing.org/prj/abstract.cfm?uri=prj-6-3-186

Graphene-based surface plasmon waveguides (SPWs) show high confinement well beyond the diffraction limit at terahertz frequencies. By combining a graphene SPW and nonlinear material, we propose a novel graphene/AlGaAs SPW structure for terahertz wave difference frequency generation (DFG) under near-infrared pumps. The composite waveguide, which supports single-mode operation at terahertz frequencies and guides two pumps by a high-index-contrast AlGaAs/AlO𝑥$\mathrm{AlGaAs}/{\mathrm{AlO}}_x$ structure, can confine terahertz waves tightly and realize good mode field overlap of three waves. The phase-matching condition is satisfied via artificial birefringence in an AlGaAs/AlO𝑥$\mathrm{AlGaAs}/{\mathrm{AlO}}_x$ waveguide together with the tunability of graphene, and the phase-matching terahertz wave frequency varies from 4 to 7 THz when the Fermi energy level of graphene changes from 0.848 to 2.456 eV. Based on the coupled-mode theory, we investigate the power-normalized conversion efficiency for the tunable terahertz wave DFG process by using the finite difference method under continuous wave pumps, where the tunable bandwidth can reach 2 THz with considerable conversion efficiency. To exploit the high peak powers of pulses, we also discuss optical pulse evolutions for pulse-pumped terahertz wave DFG processes.

© 2018 Chinese Laser Press

Abstract-Liquid crystal terahertz modulator with plasmon-induced transparency metamaterial

Jing Wang, Hao Tian, Yu Wang, Xueyan Li, Yujie Cao, Li Li, Jianlong Liu, Zhongxiang Zhou

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-5-5769

An electrically tunable terahertz (THz) modulator with large modulation depth and low insertion loss is performed with liquid crystal (LC) metamaterial. The modulation depth beyond 90% and insertion loss below 0.5 dB are achievable at normal incidence by exploiting plasmon-induced transparency (PIT) effect. The PIT spectra can be manipulated by actively controlling the interference between dipole mode and nonlocal surface-Bloch mode with LC. The incident angle tuning effect on PIT spectra shows that the large modulation depth and low insertion loss can remain over a wide range of working angles. The superior property and simplicity of design make this modulator promising in advanced terahertz communication.

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

Abstract-Guiding terahertz orbital angular momentum beams in multimode Kagome hollow-core fibers

Haisu Li, Guobin Ren, Bofeng Zhu, Yixiao Gao, Bin Yin, Jing Wang, and Shuisheng Jian

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-42-2-179

We explore terahertz (THz) orbital angular momentum (OAM) modes supported in multimode Kagome hollow-core fibers. Numerical models are adopted to characterize the effective indices and confinement losses of vector modes over 0.2–0.9 THz, where two low-loss transmission windows are observed. Linearly combining the vector modes, THz OAM states can be generated. Covering a broad bandwidth of 0.25 THz, the purity values of OAM modes are beyond 0.9. Using numerical simulations, the hollow-core THz fibers with one and two rings of Kagome structures are also comparably investigated. We reveal that the OAM purity is dependent upon the confinement performance of THz fiber.

© 2017 Optical Society of America

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Abstract-Crystal engineering approach to produce complex of azelnidipine with maleic acid

Weiguang Lian , Dong Li , Min Wang , Caiqin Yang and Jing Wang                                            
http://pubs.rsc.org/en/content/articlelanding/2013/CE/C3CE26967A

A novel azelnidipine-maleic acid complex was prepared by the solvent-assisted cogrinding method. The obtained complex was characterized by powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), infrared (IR), Raman, solid-state nuclear magnetic resonance (ssNMR), and terahertz (THz) spectroscopy. The PXRD and DSC measurement identified new different crystal form of the obtained complex other than those of the single azelnidipine and maleic acid. It was revealed that the azelnidipine-maleic acid complex was formed at a molar ratio of 2:1. IR, Raman and ssNMR spectroscopy verified that C-H...O hydrogen bond was formed between C=O from maleic acid and methyl group from azelnidipine. The distinctive THz spectrum showed that the vibrational mode of the complex was different from those of the starting materials, suggesting that THz spectroscopy is an ideal tool to evaluate complex formation. The solubilities of azelnidipine in maleic acid with different concentrations at different temperatures were investigated; the obtained values were used to calculate the formation constants and thermodynamic parameters. The improved dissolution rate in vitro of the complex showed potential to improve the physicochemical properties of azelnidipine API by crystal engineering approach