Abstract-Evanescent resonant mode for a T-shaped cavity in a terahertz parallel-plate waveguide

Kai Wang, Qing Cao, Huifang Zhang, Pengcheng Shen, and Lujing Xing

https://www.osapublishing.org/ao/abstract.cfm?uri=ao-57-27-7967

The evanescent resonant modes are proposed for a T-shaped cavity in a terahertz (THz) parallel-plate waveguide (PPWG) to understand the essence of the resonant phenomenon. The theoretical modal field and the resonant frequency of the TE2${}_{\mathrm{}}$-like evanescent resonant mode show agreement with the simulated ones through the whole THz region. The modal field consists of three evanescent fields outside the cross region and one propagation field inside the cross region. When the TE2${}_{\mathrm{}}$-like mode is excited, the input THz wave is reflected. The resonance frequency of the TE2${}_{\mathrm{}}$-like mode depends closely on the geometrical parameters of the T-shaped cavity. In particular, the separation of the PPWG must be twice larger than the width of the groove to avoid the non-evanescent electric field in the groove. In addition, the electric field of the TE1${}_{\mathrm{}}$-like mode is localized in the T-shaped cavity. These results have potential applications in field enhancement, sensors, and filters.

© 2018 Optical Society of Americahttps://www.osapublishing.org/ao/abstract.cfm?uri=ao-57-27-7967

Abstract-Interferometric control of dual-band terahertz perfect absorption using a designed metasurface

Ming Kang, Huifang Zhang, Xueqian Zhang, Quanlong Yang, Weili Zhang,  Jiaguang Han

https://journals.aps.org/prapplied/accepted/b3077A50X33E621a909b163840c172b9fbca3365e

Coherent perfect absorber (CPA), a time-reversed counterpart to the laser emission, could cause all energy fed to the system to be absorbed. It can also be as an absorptive interferometer, which could provide applications in controllable optical energy transfer. Here, in order to achieve terahertz CPA, we propose a designed metasurface and experimentally demonstrate that it can serve as a polarization-insensitive CPA at one-frequency channel under normal symmetric excitation, while a transverse electric (TE) CPA at two-frequency channels around oblique ${40}^o$symmetric incidence. Such phenomena in this system can be attributed to Fano resonance consisting of interacting one bright and one dark modes under normal incidence and an additional operative dark mode under oblique symmetric excitation. The experimental results finds good agreement with the fitted coupled mode theory(CMT). Moreover, we show the output amplitude can be effectively tuned from 0 to 1 only by varying the relative phase between the two input waves. The designed CPA could find potential application in effectively controlling absorption for terahertz imaging and terahertz switches.

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-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-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.