Abstract-Manipulation terahertz wave with electro-rheological fluid

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 Li Jiu-sheng, Hu Mu-shu,

https://www.sciencedirect.com/science/article/abs/pii/S0030401820306611

Diverse applications of terahertz technology depend on the efficient manipulation of terahertz beam. Terahertz switch with transmitting electromagnetic intensity tunability is essential for effective control of terahertz wave. Existing approaches are a lack of simple structure able to achieve superior switching performance. Here we experimentally demonstrate a new approach to manipulate terahertz wave transmittance controlled by Calcium and Titanium Precipitate (CTP) electro-rheological (ER) fluid, and develop a novel CTP ER-fluid switch at terahertz frequencies based on this mechanism. In this way, we achieve perfect terahertz wave intensity switching through actively adjusting the external applied electric field. This operating principle ensures that our presented device can operate in terahertz frequency range.

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
• 
  
• 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.

Abstract-Double-Layer Frequency Selective Surface for Terahertz Bandpass Filter

Xiong Ri-Hui, Li Jiu-Sheng

https://link.springer.com/article/10.1007/s10762-018-0527-x

A thin, low-cost, double-layer frequency-selective surface (FSS) bandpass filter has been designed, fabricated, and measured for operation in the terahertz band. The present FSS structure is composed of double-layer tin foil with a hexagonal lattice array of circular holes. A flat passband is observed with a 3-dB bandwidth of 0.20 THz from 0.81 to 1.01 THz, which is about 22% relative to the center frequency. This bandpass filter based on double-layer FSS structures achieved average insertion loss of 0.7-dB and 106.31-dB/THz band-edge steepness. We have found good agreement between theoretical calculations and experimental results.

Abstract-Flexible manipulation of terahertz wave reflection using polarization insensitive coding metasurfaces

Li Jiu-sheng, Zhao Ze-jiang, and Yao Jian-quan

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-24-29983

In order to extend to 3-bit encoding, we propose notched-wheel structures as polarization insensitive coding metasurfaces to control terahertz wave reflection and suppress backward scattering. By using a coding sequence of “00110011…” along x-axis direction and 16 × 16 random coding sequence, we investigate the polarization insensitive properties of the coding metasurfaces. By designing the coding sequences of the basic coding elements, the terahertz wave reflection can be flexibly manipulated. Additionally, radar cross section (RCS) reduction in the backward direction is less than −10dB in a wide band. The present approach can offer application for novel terahertz manipulation devices.

© 2017 Optical Society of America

Abstract-Switching terahertz wave with grating-coupled Kretschmann configuration

Li Jiu-sheng

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-16-19422

We present a terahertz wave switch utilizing Kretschmann configuration which consists of high-refractive-index prism-liquid crystal-periodically grooved metal grating. The switching mechanism of the terahertz switch is based on spoof surface plasmon polariton (SSPP) excitation in the attenuated total reflection regime by changing the liquid crystal refractive index. The results highlighted the fact that the feasibility to “tune” the attenuated total reflection terahertz wave intensity by using the external applied bias voltage. The extinction ratio of the terahertz switch reaches 31.48dB. The terahertz switch has good control ability and flexibility, and can be used in potential terahertz free space device systems.

© 2017 Optical Society of America

Abstract-Numerical analysis of temperature-controlled terahertz power splitter

Li Yang, Li Jiu-Sheng

https://jeos.springeropen.com/articles/10.1186/s41476-017-0039-7

Background

As a significant terahertz functional device, terahertz beam splitters with high performance are highly required to meet the need for terahertz communication, terahertz image, and terahertz sensor systems.

Results

The proposed 1×6 power splitter becomes 1×4 power splitter with the aid of the localized temperature change at the frequency of 1.0THz. The total output power is equivalent to 97.8% of the input power for the six-channel splitter and 95.4% for the four-channel splitter. The dimension of the device is of 35a×27a.

Conclusions

A temperature-controlled terahertz power divider based on photonic crystal multimode interference structure and Y-junction photonic crystal waveguides is an efficient mechanism for the power divider of terahertz waves. The proposed device paves a promising way for the realization of terahertz wave integrated device.

Abstract-Terahertz wave polarization splitter using full band-gap photonic crystals

Sun Jian-zhong,  

Li Jiu-sheng

http://link.springer.com/article/10.1007/s10762-014-0131-7

Manipulation of terahertz wave polarization state exhibits tremendous potential in developing application of terahertz science and technology. A terahertz polarization beam splitter based on three linear defect photonic crystal waveguides is designed and numerically demonstrated. Both plane wave expansion method and finite-difference time-domain method are used to calculate and analyze the characteristics of the proposed device. The simulation results show that the designed polarization beam splitter can split TE and TM polarized mode into different propagation directions with high efficiency in the frequency range from 1.225THz to 1.260THz. Especially, the extinction ratios for both TE and TM modes are larger than 20dB.

Abstract-High absorption terahertz-wave absorber consisting of dual-C metamaterial structure

1. Li Jiu-Sheng

http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fmop.27468

We report a perfect absorber based on dual-C metamaterial structure operating in the terahertz regime.The proposed structure ism numerically investigated by the CST Microwave Studio. By manipulating the periodic patterned structures as well as the dielectric layer material, significantly high absorption can be obtained at specific resonance frequency. The fabricated device has been characterized using a Fourier transform infrared spectrometer. The experimental results show that the distinct absorption peak at 0.573 THz with absorption magnitudes of 0.996, which is in good agreement with the simulation.