Abstract-A flexible, multifunctional, active terahertz modulator with an ultra-low triggering threshold

He Ma,   Yu Wang,   Rong Lu,   Fangrui Tan,  Yulan Fu,  Guang Wang,  Dayong Wang,  Kai Liu,   Shoushan Fan,  Kaili Jiang  Xinping Zhang 

https://pubs.rsc.org/en/content/articlelanding/2020/tc/d0tc02446e#!divAbstract

Active terahertz (THz) modulators play an essential role in THz technology. Because of the excellent THz modulation properties bestowed by its intrinsic metal-insulator transition (MIT) at 68 °C, vanadium dioxide (VO2) is an appealing active THz modulator material. Current active THz modulator designs based on pure VO2 films or metasurfaces deposited on traditional semiconductor substrates are typically subject to high triggering thresholds and slow responses. Therefore, further development of VO2 active THz modulators for superior performance requires new material and device designs. In this paper, we develop a flexible active THz modulator based on an aligned carbon nanotube thin film coated with VO2. THz wave modulation driven by the MIT of VO2 presents a giant modulation depth up to 91% and broad bandwidth (>2.3 THz). Various stimuli can be utilized to trigger the THz modulator. The response time of the THz modulator is 27 ms, which can be further shortened by decreasing the device size. In addition, the light-triggering threshold is quite low (0.58 mW/mm2). Optical anisotropy enables polarization of the THz modulator. Since they combine superior modulation performance, responsive stimuli diversity, versatility, and flexibility, these active THz modulators find applications in THz communication, THz imaging, etc.

Abstract-Multi-layered full-field phase imaging using continuous-wave terahertz ptychography

Dayong Wang, Bing Li, Lu Rong, Fangrui Tan, John J. Healy, Jie Zhao, and Yunxin Wang

https://www.blogger.com/blogger.g?blogID=124073320791841682#editor/target=post;postID=6482707098183844787

Due to the unique properties of terahertz (THz) waves, THz phase imaging has been widely investigated to retrieve the absorption and phase modulation of dielectric two-dimensional thin samples, as well as multiple stacked samples. In this Letter, we apply the three-dimensional ptychographic iterative engine algorithm for continuous-wave THz full-field multi-layered phase imaging. The complex-valued transmission function of two-layered polypropylene thin plates and the corresponding probe function are reconstructed, respectively, which are immune to crosstalk of different layers. The phenomenon of the field-of-view enlargement at the second object layer is observed. This lensless compact imaging method can be potentially used for THz three-dimensional imaging.

© 2020 Optical Society of America

Abstract-Probe position correction based on overlapped object wavefront cross-correlation for continuous-wave terahertz ptychography

Lu Rong, Chao Tang, Dayong Wang, Bing Li, Fangrui Tan, Yunxin Wang, and Xiaoyu Shi

Fig. 1 A schematic representation of the proposed algorithm. If the initial probe position is determined, the following probe positions are successively estimated by Eqs. (2) – (5).

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-27-2-938

Continuous-wave terahertz ptychography is a promising large field-of-view lensless terahertz phase imaging method. Inaccurate probe positions would severely degrade the reconstruction quality, as compared to other spectral bands. In this paper, we propose a probe position correction method based on cross-correlation registration on overlapped regions of the object wavefront for terahertz ptychography. The translation errors could be minimized in the order of 0.01 pixels. The simulation results suggest good computational efficiency, correction, and reconstruction accuracy. We perform continuous-wave terahertz ptychography on a cicada’s forewing. The subcosta and the first radius vein are distinguished after position correction. The probe position distribution reveals that the tilt angle between the object plane and the recording plane is 0.26°.

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