Abstract-Printing special surface components for THz 2D and 3D imaging

                                                                 

Bo Yan, Zhigang Wang, Xing Zhao, Lie Lin, Xiaolei Wang, Cheng Gong,  Weiwei Liu

https://www.nature.com/articles/s41598-020-77998-9

The paper reports an off-axis large focal depth THz imaging system which consists of three 3D printed special surface components (two aspherical mirrors and an axicon). Firstly, the optical design software is used to design and optimize the aspherical parabolic mirror. Secondly, the optimized mirror is prepared by a 3D printing and metal cladding method. Thirdly, a THz axicon is designed for generation of quasi-Bessel Beam and a new geometric theoretical model of oblique incident light for axicon is established. Finally, the imaging system based on the special surface components is constructed. Its maximum diffraction-free distance is about 60 mm, which is 6 times higher than the traditional system. To verify the effectiveness, THz two-dimensional imaging experiments and three-dimensional computed tomography experiment are carried out. The results are consistent with the design and calculations.

Abstract-Tunable reflecting terahertz filter based on chirped metamaterial structure

• Jing Yang
• , Cheng Gong
• , Lu Sun
• , Ping Chen
• , Lie Lin
•  & Weiwei Liu

http://www.nature.com/articles/srep38732
Tunable reflecting terahertz bandstop filter based on chirped metamaterial structure is demonstrated by numerical simulation. In the metamaterial, the metal bars are concatenated to silicon bars with different lengths. By varying the conductivity of the silicon bars, the reflectivity, central frequency and bandwidth of the metamaterial could be tuned. Light illumination could be introduced to change the conductivity of the silicon bars. Numerical simulations also show that the chirped metamaterial structure is insensitive to the incident angle and polarization-dependent. The proposed chirped metamaterial structure can be operated as a tunable bandstop filter whose modulation depth, bandwidth, shape factor and center frequency can be controlled by light pumping.

Abstract-Strong Spatial Confinement of Terahertz Wave inside Femtosecond Laser Filament

Jiayu Zhao, Wei Chu, Zhi Wang, Yan Peng, Cheng Gong, Lie Lin, Yiming Zhu, Weiwei Liu, Ya Cheng, Songlin Zhuang, and Zhizhan Xu

ACS Photonics, Just Accepted Manuscript

DOI: 10.1021/acsphotonics.6b00512

Publication Date (Web): November 8, 2016

Copyright © 2016 American Chemical Society

http://pubs.acs.org/doi/abs/10.1021/acsphotonics.6b00512

In this paper, a new experimental phenomenon is demonstrated. During the femtosecond laser filamentation, the generated terahertz (THz) pulse has been found to be strongly confined inside the plasma channel, reaching a spatial diameter of a few tens of micrometres. It has been attributed to the formation of a plasma negative dielectric waveguide induced by the transverse inhomogeneous plasma density distribution. The new experimental phenomenon will renew the understanding of the THz wave generation and propagation dynamics during the femtosecond laser and air plasma interaction. Due to this strong spatial confinement, THz electric field strength could be enhanced by orders of magnitude, potentially providing a new approach to perform THz nonlinear optics with low laser energy.

Abstract-3D printed low-loss THz waveguide based on Kagome photonic crystal structure

Jing Yang, Jiayu Zhao, Cheng Gong, Haolin Tian, Lu Sun, Ping Chen, Lie Lin, and Weiwei Liu

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-24-20-22454

A low-loss hollow core terahertz waveguide based on Kagome photonic crystal structure has been designed and fabricated by 3D printing. The 3D printed waveguide has been characterized by using THz time-domain spectroscopy. The results demonstrate that the obtained waveguide features average power propagation loss of 0.02 cm−1 for 0.2-1.0 THz (the minimum is about 0.002 cm−1 at 0.75 THz). More interesting, it could be simply mechanically spliced without any additional alignment, while maintaining the excellent performance. The 3D printing technique will be a promising solution to fabricate Kagome THz waveguide with well controllable characteristics and low cost.

© 2016 Optical Society of America

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