Abstract-Terahertz wave front manipulation based on Pancharatnam-Berry coding metasurface

Li Shao-he, Li Jiu-sheng, and Sun Jian-Zhong

Fig. 1. Design of the basic coding particle. (a) Schematic diagram of the basic coding particle. Reflection magnitude of the basic coding particle under normal incidence of LCP (b) and RCP (c) waves. Here, RLL(RRR) and RRL(RLR) are the reflection magnitude with co-polarization and cross-polarization under normally incident LCP (RCP) waves, respectively. (d) Reflection phase and amplitude values under normal incidence of x- and y linearly polarized waves, respectively.

https://www.osapublishing.org/ome/abstract.cfm?uri=ome-9-3-1118

We design a coding metasurface based on Pancharatnam-Berry (PB) phase to manipulate terahertz waves, which is simple and flexible. Compared with the previous design of the coding metasurface, the present coding particles can be obtained by using a same size meta-particle with various orientations instead of designing multiple structures or changing specific size parameters. The PB coding metasurfaces composed of U-shaped particles with pre-designed coding sequences can generate multi-bit coding in the terahertz frequencies and control the reflected terahertz waves to the various directions. Both simulation and theoretical calculation scattering patterns of the designed PB coding metasurfaces demonstrate the expected manipulations. Additionally, the bandwidth of radar cross section (RCS) reduction of approaching −15 dB is 1.05THz (range from 0.9THz to 1.95THz). We believe that the proposed design provides a more flexible way for the manipulation of reflected terahertz waves.

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

Abstract-Terahertz modulator a using CsPbBr3 perovskite quantum dots heterostructure

• Li Shao-he, 
• Li Jiu-sheng
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• https://link.springer.com/article/10.1007/s00340-018-7094-7

A novel terahertz wave modulator based on CsPbBr3 perovskite quantum dots heterostructure is proposed. An external modulated 450 nm pumping laser is utilized to generate photoexcited free carriers at the CsPbBr3 perovskite quantum dots heterostructure medium. We measured an amplitude modulation of the terahertz transmission in the frequency range from 0.23 to 0.35 THz with various laser intensity irradiances. In addition, dynamic amplitude modulation at 0.27 THz carrier wave show that the modulator provides a modulation speed of 2.5 MHz at a external pump laser irradiance of 2.0 W/cm2. Our CsPbBr3 perovskite quantum dots heterostructure can high speed modulation and can be used for terahertz modulation in addition to photovoltaics application

Abstract- Terahertz Modulator Using 4-N,N-Dimethylamino-4′-N′-Methyl-Stilbazolium Tosylate (DAST)/Si Hybrid Structure

Li Jiu-sheng, Li Shao-he, Zhang Le,

(a) The image of the prepared DAST-Si sample, (b) Scanning microscope images of DAST film surface, (c) Raman spectra of the prepared DAST film, and (d) X-ray diffraction spectrum of the DAST film

https://ieeexplore.ieee.org/document/8306983/

Terahertz high-data communication creates numerous demands for terahertz wave amplitude modulation. Here, we experimentally demonstrate a high-speed terahertz wave modulator based on 4-N,N-dimethylamino-4'-N'-methyl-stilbazolium tosylate (DAST)/Si hybrid structure. An externally modulated 808-nm pumping laser is utilized to generate photoexcited free carriers at the DAST medium. With the increase of illumination laser intensity, the modulation depth continues to increase in the frequency range from 0.23 to 0.35 THz. A dynamic amplitude modulation at 0.25-THz carrier wave shows that the our modulator provides a modulation speed of 1.26 MHz with a depth of up to 53% at an external pump laser irradiance of 3.5 W/cm2. Our present DAST/Si hybrid structure provides a practicable route to achieve effective signal modulation for terahertz communication system.