Abstract-High-efficiency terahertz devices based on cross-polarization converter

• Huan Zhao, 
• Xinke Wang, 
• Jingwen He, 
• Jinying Guo, 
• Jiasheng Ye, 
• Qiang Kan,  
• Yan Zhan

• https://www.nature.com/articles/s41598-017-18013-6#Sec2

Metasurface-based devices have been investigated intensively because of their attractive properties but these devices generally suffer from low efficiency. Here we demonstrate several high-efficiency terahertz (THz) devices based on cross-polarization converters that is composed of bilayer metasurface-based structures. The converter can transfer the polarization states of transmitted THz waves from the x-direction into the y-direction with an experimental conversion efficiency of 85%. This high-efficiency transfer mechanism is investigated in detail. Furthermore, this kind of devices can be fabricated easily. A THz metalens is designed and fabricated and its focusing and imaging properties are investigated experimentally. A pure phase THz hologram that can generate different images on different propagation planes is also designed and the image reconstruction capabilities of the phase holograms are demonstrated experimentally. The performance levels of all designed devices show excellent agreement between the theoretical expectations and the corresponding experimental results. This technology may pave the way towards practical applications of such metasurface devices.

Abstract-A broadband terahertz ultrathin multi-focus lens

• Jingwen He
• , Jiasheng Ye
• , Xinke Wang
• , Qiang Kan
•  & Yan Zhang

http://www.nature.com/articles/srep28800

Ultrathin transmission metasurface devices are designed on the basis of the Yang-Gu amplitude-phase retrieval algorithm for focusing the terahertz (THz) radiation into four or nine spots with focal spacing of 2 or 3 mm at a frequency of 0.8 THz. The focal properties are experimentally investigated in detail, and the results agree well with the theoretical expectations. The designed THz multi-focus lens (TMFL) demonstrates a good focusing function over a broad frequency range from 0.3 to 1.1 THz. As a transmission-type device based on metasurface, the diffraction efficiency of the TMFL can be as high as 33.92% at the designed frequency. The imaging function of the TMFL is also demonstrated experimentally and clear images are obtained. The proposed method produces an ultrathin, low-cost, and broadband multi-focus lens for THz-band application

Abstract-Abruptly autofocusing terahertz waves with meta-hologram

Abruptly autofocusing terahertz waves with meta-hologram

ingwen He, Sen Wang, Zhenwei Xie, Jiasheng Ye, Xinke Wang, Qiang Kan, and Yan Zhang

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-41-12-2787

An abruptly autofocusing ring-Airy beam is demonstrated in the terahertz (THz) waveband with a meta-hologram. The designed meta-hologram is composed of gold C-shaped slot antennas, which can realize both phase and amplitude modulation of the incident THz wave. A THz holographic imaging system is utilized to measure the generated ring-Airy beam; an abrupt focus following a parabolic trajectory is subsequently observed. THz ring-Airy beams with different parameters are also generated and investigated. This method can be expanded to other wavebands, such as the visible band, for which the meta-hologram can replace traditional computer-generated holography to avoid undesirable multiple diffraction orders.

© 2016 Optical Society of America

Abstract-An ultrathin terahertz lens with axial long focal depth based on metasurfaces

Xiao-Yan Jiang,¹ Jia-Sheng Ye,^1,2,* Jing-Wen He,^1,3 Xin-Ke Wang,^1,2 Dan Hu,^1,3 Sheng-Fei Feng,^1,2 Qiang Kan,⁴ and Yan Zhang^1,2,3,5

¹Department of Physics, Capital Normal University and Beijing Key Lab for THz Spectroscopy and Imaging, Key Lab of THz Optoelectronics, Ministry of Education, Beijing 100048, China

²Beijing Center for Mathematics and Information Interdisciplinary Sciences, Harbin Institute of Technology, Harbin 150001, China

³Department of Physics, Harbin Institute of Technology, Harbin 150001, China

⁴State Key Laboratory for integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China

⁵yzhang@mail.cnu.edu.cn

^*Corresponding author: jiashengye@gmail.com

http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-21-24-30030

The plasmonic resonance effect on metasurfaces generates an abrupt phase change. We employ this phase modulation mechanism to design the longitudinal field distribution of an ultrathin terahertz (THz) lens for achieving the axial long-focal-depth (LFD) property. Phase distributions of the designed lens are obtained by the Yang-Gu iterative amplitude-phase retrieval algorithm. By depositing a 100 nm gold film on a 500 μm silicon substrate and etching arrayed V-shaped air holes through the gold film, the designed ultrathin THz lens is fabricated by the micro photolithography technology. Experimental measurements have demonstrated its LFD property, which basically agree with the theoretical simulations. In addition, the designed THz lens possesses a good LFD property with a bandwidth of 200 GHz. It is expected that the designed ultrathin LFD THz lens should have wide potential applications in broadband THz imaging and THz communication systems.
© 2013 Optical Society of America