Abstract-Polarization-independent all-silicon dielectric metasurfaces in the terahertz regime

Huifang Zhang, Xueqian Zhang, Quan Xu, Qiu Wang, Yuehong Xu, Minggui Wei, Yanfeng Li, Jianqiang Gu, Zhen Tian, Chunmei Ouyang, Xixiang Zhang, Cong Hu, Jiaguang Han, and Weili Zhang

https://www.osapublishing.org/prj/abstract.cfm?uri=prj-6-1-24&origin=search

Dielectric metasurfaces have achieved great success in realizing high-efficiency wavefront control in the optical and infrared ranges. Here, we experimentally demonstrate several efficient, polarization-independent, all-silicon dielectric metasurfaces in the terahertz regime. The metasurfaces are composed of cylindrical silicon pillars on a silicon substrate, which can be easily fabricated using etching technology for semiconductors. By locally tailoring the diameter of the pillars, full control over abrupt phase changes can be achieved. To show the controlling ability of the metasurfaces, an anomalous deflector, three Bessel beam generators, and three vortex beam generators are fabricated and characterized. We also show that the proposed metasurfaces can be easily combined to form composite devices with extended functionalities. The proposed controlling method has promising applications in developing low-loss, ultra-compact spatial terahertz modulation devices.

© 2017 Chinese Laser Press

Abstract-Multi-wavelength lenses for terahertz surface wave

Minggui Wei, Quanlong Yang, Quan Xu, Xueqian Zhang, Yanfeng Li, Jianqiang Gu, Jiaguang Han, and Weili Zhang

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-21-24872

Metasurface-based surface wave (SW) devices working at multi-wavelength has been continuously arousing enormous curiosity recently, especially in the terahertz community. In this work, we propose a multi-layer metasurface structure composed of metallic slit pairs to build terahertz SW devices. The slit pair has a narrow bandwidth and its response frequency can be altered by its geometric parameter, thereby suppressing the frequency crosstalk and reducing the difficulty of design. By elaborately tailoring the distribution of the slit pairs, a series of achromatic SW lenses (SWLs) working at 0.6, 0.75 and 1 THz are experimentally demonstrated by the near field scanning terahertz microscope (NSTM) system. In addition, a wavelength-division-multiplexer (WDM) is further designed and implemented, which is promising in building multiplexed devices for plasmonic circuits. The structure proposed here cannot only couple the terahertz wave from free space to SWs, but also control its propagation. Moreover, our findings demonstrate the great potential to design multi-wavelength plasmonic metasurface devices, which can be extended to microwave and visible frequencies as well.

© 2017 Optical Society of America

Abstract-Polarization and Frequency Multiplexed Terahertz Meta-Holography

Authors

http://onlinelibrary.wiley.com/doi/10.1002/adom.201700277/full

Seeking effective and precise control over electromagnetic waves has always been an important focus in optics. Advances in nanofabrication technology have led to designer metasurfaces, which open up new possibilities by allowing almost arbitrary spatial distributions of optical properties to be realized. This study demonstrates a multiplexed meta-hologram generating different images for different polarizations and different terahertz frequencies. By utilizing C-shape bar resonators as the basic unit cells, simultaneous binary amplitude modulation and binary phase modulation in each pixel is realized. With polarization and frequency selective independent simultaneous control of amplitude and phase in every pixel, the proposed meta-hologram makes use of all four fundamental properties of electromagnetic waves. Generation of holographic images of “C,” “F,” “T,” or “W” depending on polarization and frequency is demonstrated theoretically and experimentally. This approach, allowing for modulation of all characteristics of electromagnetic waves, paves the way for designing complex metasurfaces and metaholograms with multiplexed functionalities, which may have applications in multichannel communication and data storage.

Abstract-Ultrathin metasurface-based carpet cloak for terahertz wave

Minggui Wei, Quanlong Yang, Xueqian Zhang, Yanfeng Li, Jianqiang Gu, Jiaguang Han, and Weili Zhang

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-14-15635

Ultrathin metasurfaces with local phase compensation deliver new schemes to cloaking devices. Here, a large-scale carpet cloak consisting of an ultrathin metasurface is demonstrated numerically and experimentally in the terahertz regime. The proposed carpet cloak is designed based on discontinuous-phase metallic resonators fabricated on a polyimide substrate, offering a wide range of reflection phase variations and an excellent wavefront manipulation along the edges of the bump. The invisibility is verified when the cloak is placed on a reflecting triangular surface (bump). The multi-step discrete phase design method would greatly simplify the design process and is probable to achieve large-dimension cloaks, for applications in radar and antenna systems as a thin, lightweight, and easy-to-fabricate solution for radio and terahertz frequencies.

© 2017 Optical Society of America

Abstract-Polarization and Frequency Multiplexed Terahertz Meta-Holography

Qiu Wang, Xueqian Zhang, Eric Plum, Quan Xu, Minggui Wei, Yuehong Xu, Huifang Zhang, Yi Liao, Jianqiang Gu, Jiaguang Han, Weili Zhang

http://onlinelibrary.wiley.com/doi/10.1002/adom.201700277/full

Seeking effective and precise control over electromagnetic waves has always been an important focus in optics. Advances in nanofabrication technology have led to designer metasurfaces, which open up new possibilities by allowing almost arbitrary spatial distributions of optical properties to be realized. This study demonstrates a multiplexed meta-hologram generating different images for different polarizations and different terahertz frequencies. By utilizing C-shape bar resonators as the basic unit cells, simultaneous binary amplitude modulation and binary phase modulation in each pixel is realized. With polarization and frequency selective independent simultaneous control of amplitude and phase in every pixel, the proposed meta-hologram makes use of all four fundamental properties of electromagnetic waves. Generation of holographic images of “C,” “F,” “T,” or “W” depending on polarization and frequency is demonstrated theoretically and experimentally. This approach, allowing for modulation of all characteristics of electromagnetic waves, paves the way for designing complex metasurfaces and metaholograms with multiplexed functionalities, which may have applications in multichannel communication and data storage.

Abstract-Broadband and wide-angle RCS reduction using a 2-bit coding ultrathin metasurface at terahertz frequencies

• Lanju Liang
• , Minggui Wei
• , Xin Yan
• , Dequan Wei
• , Dachuan Liang
• , Jiaguang Han
• , Xin Ding
• , GaoYa Zhang
•  & Jianquan Yao

http://www.nature.com/articles/srep39252

A novel broadband and wide-angle 2-bit coding metasurface for radar cross section (RCS) reduction is proposed and characterized at terahertz (THz) frequencies. The ultrathin metasurface is composed of four digital elements based on a metallic double cross line structure. The reflection phase difference of neighboring elements is approximately 90° over a broadband THz frequency. The mechanism of RCS reduction is achieved by optimizing the coding element sequences, which redirects the electromagnetic energies to all directions in broad frequencies. An RCS reduction of less than −10 dB bandwidth from 0.7 THz to 1.3 THz is achieved in the experimental and numerical simulations. The simulation results also show that broadband RCS reduction can be achieved at an incident angle below 60° for TE and TM polarizations under flat and curve coding metasurfaces. These results open a new approach to flexibly control THz waves and may offer widespread applications for novel THz devices.