Abstract-Temperature-controlled terahertz polarization conversion bandwidth

 

Jing Zhao, Chunmei Ouyang, Xieyu Chen, Yanfeng Li, Caihong Zhang, Longcheng Feng, Biaobing Jin, Jiajun Ma, Yi Liu, Shoujun Zhang, Quan Xu, Jiaguang Han,  Weili Zhang, 

Schematic diagram of the metasurface structure and experimental system. (a) Unit cell, composed of sapphire substrate, VO2 and gold SRRs layers, polyimide dielectric layer and a gold grating, with geometrical parameters h = 2000 µm, P = 80 µm, d = 200 nm, t = 35 µm, d1 = 10 µm, and d2 = 22 µm. (b) Vertical view of the unit cell. (c) Gold SRR with geometrical parameters O = 10°, O1 = 10°, C1 = 30°, and C2 = 45°. (d)-(f) Optical microscope images of the fabricated VO2 and gold SRRs, gold grating and their combined structure, respectively. (g) Sample characterization by THz-TDS.

https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-29-14-21738&id=452731

Active control of metasurfaces has attracted widespread attention because of the adjustable electromagnetic properties obtained. Here we designed and experimentally studied a dynamically controllable polarization converter in the terahertz band. By designing the structural parameters and utilizing the insulator-to-metal phase transition of vanadium dioxide and principle of current resonance, dynamic tunability of the polarization conversion function from dual-broadband (0.45∼0.77 THz and 0.97∼1.2 THz) to ultra-broadband (0.38∼1.20 THz) can be realized with a high polarization conversion ratio. The scheme proposed here can find potential applications in integrated terahertz systems, sensing, imaging and communications areas.

© 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Four resonators based high sensitive terahertz metamaterial biosensor used for measuring concentration of protein

Yuanyuan Li, Xieyu Chen, Fangrong Hu, Dongxia Li, Huan Teng, Qi Rong, Wentao zhang, Jiaguang Han,  Huasheng Liang

http://iopscience.iop.org/article/10.1088/1361-6463/aaf7e9

A terahertz (THz) metamaterial biosensor based on four identical resonators is experimentally demonstrated, and high sensitivity is achieved by exciting four synchronous LC oscillations in a unit cell. The effect of geometries on the resonance frequency of the sensor is investigated using finite integration time domain (FIDT) method, and the simulated sensitivity is 85 GHz per refractive index unit (RIU). The biosensor sample is fabricated using a surface micromachining process and characterized by a THz time domain spectroscopy (TDS) system combined with bovine serum albumin (BSA) solution as anelyte. The experimental results indicate that the resonance frequency shows distinct redshift when increases the concentration of BSA solution. When the concentration is high up to 765μmol/L, the frequency shift reaches 50 GHz, and the measurable minimum concentration is low to 1.5μmol/L. The biosensor is small in shape, wide in measurable range, convenient in operation and rapid in detection, which is of great significance for rapid concentration measurement, biomolecules detection and disease diagnosis.

Abstract-Broadband terahertz rotator with an all-dielectric metasurface

Quanlong Yang, Xieyu Chen, Quan Xu, Chunxiu Tian, Yuehong Xu, Longqing Cong, Xueqian Zhang, Yanfeng Li, Caihong Zhang, Xixiang Zhang, Jiaguang Han, and Weili Zhang

Fig. 1. (a) Conceptual description of the metasurface based on two identical dielectric antennas to manipulate the polarization of the terahertz wave. 𝛼$\alpha$ and 𝛽$\beta$ represent the orientations of two dielectric antennas (marked by the orange arrows), and 𝛾$\gamma$ is the effective optical axis orientation from the superposition of two antennas (marked by the navy arrow). (b) Schematic illustration of the two silicon antennas with geometrical parameters 𝑊=45  μm$W=45\mathrm{\mu m}$, 𝐿=180  μm$L=180\mathrm{\mu m}$, 𝐻=200  μm$H=200\mathrm{\mu m}$, and period 𝑃=375  μm$P=375\mathrm{\mu m}$. (c),(d) Schematic diagrams for high-quality polarization generation. Without introducing the phase gradient, both the 𝑥$x$-polarized and 𝑦$y$-polarized light propagates in the normal direction forming dispersive polarization states within the frequency range of interest. The phase gradient enables spatial separation of the two orthogonal polarization components, giving rise to pure linearly polarized components within a broad frequency range.

https://www.osapublishing.org/prj/fulltext.cfm?uri=prj-6-11-1056&id=399205

Polarization manipulation is essential in developing cutting-edge photonic devices ranging from optical communication displays to solar energy harvesting. Most previous works for efficient polarization control cannot avoid utilizing metallic components that inevitably suffer from large ohmic loss and thus low operational efficiency. Replacing metallic components with Mie resonance-based dielectric resonators will largely suppress the ohmic loss toward high-efficiency metamaterial devices. Here, we propose an efficient approach for broadband, high-quality polarization rotation operating in transmission mode with all-dielectric metamaterials in the terahertz regime. By separating the orthogonal polarization components in space, we obtain rotated output waves with a conversion efficiency of 67.5%. The proposed polarization manipulation strategy shows impressive robustness and flexibility in designing metadevices of both linear- and circular-polarization incidences.

© 2018 Chinese Laser Press

Abstract-Anisotropic plasmonic response of black phosphorus nanostrips in terahertz metamaterials

Qingqing Fo,  Ling Pan, Xieyu Chen, Quan Xu, Chunmei Ouyang, Xueqian Zhang,   Zhen Tian, Jianqiang Gu, Liyuan Liu,   Jiaguang Han,  Weili Zhang

https://ieeexplore.ieee.org/document/8369157/

Two-dimensional black phosphorus (BP) recently emerged as an outstanding material for optoelectronics and nanophotonics applications. In contrast to graphene, BP has a sufficiently large electronic bandgap and its high carrier mobility allows for efficient free-carrier absorption in the infrared and terahertz regimes. Here, we present a reflective structure to enhance the response of nanostructured monolayer BP at terahertz frequencies and investigate localized surface plasmon resonances in BP nanostrip arrays. Anisotropic absorption is observed in the proposed BP metamaterials due to the puckered crystal structure of monolayer BP, and further investigations show that the plasmonic resonances are strongly depending on the geometric parameters of the nanostrips and the coupling between the adjacent nanostrips. We expect that the monolayer BP is an outstanding candidate of highly anisotropic plasmonic material for ultra-scaled optoelectronic integration.