Abstract-A Modularized and Switchable Component for Flexible Passive Device: Terahertz Photonic Crystals with Fine‐Tuning

Jiannan Gao, Rong Wang, Qian Zhao, Bo Li, Ji Zhou,




https://onlinelibrary.wiley.com/doi/abs/10.1002/adom.201800384?af=R

In this work, tunable terahertz photonic crystals (PCs) used as modularized and switchable components in flexible passive device are designed and prepared. Flexible woodpile structures created by the direct‐writing technology with a composite ink system composed of barium strontium titanate nanoparticles and polydimethylsiloxane are immersed in 5CB liquid crystals (LCs), where the orientation of LC molecule is modulated by the external magnetic field. Each of these can work in terahertz wavelength with specific position and depth of the dips in the transmittance spectra due to different geometries as well as having the ability of fine‐tuning. Experiments show that the photonic gaps of these PCs can cover from 0.2 to 0.3 THz, as well as about 7.5% fine tunability of photonic gap appearing with the orientation change of the magnetic field. More interestingly, the dips of photonic gaps keep the same position but become deeper with the increase of layer, an ability to realize another dimensional switchover. This work demonstrates that efficient terahertz PCs with different geometry parameters could be dynamically tuned by the orientation of magnetic field and it can open a universal approach to shrinking the size of device and rapid manufacturing in a large throughput.

Abstract-Experimental realization of Mie-resonance terahertz absorber by self-assembly method

Jiannan Gao, Chuwen Lan, Qian Zhao, Bo Li, and Ji Zhou

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-10-13001

Mie-resonance terahertz absorbers by self-assembly method are designed and demonstrated in experiments and simulations. A monolayer of zirconium dioxide (ZrO2) microspheres fixed on a copper film with designed grids that were manufactured by direct writing with a composite ink system composed of polydimethylsiloxane (PDMS). More importantly, different spacing and array configurations were created economically and efficiently, showing visual performance. Magnetic resonance leads to near-unity absorption at about 0.4 THz in the samples. This work demonstrates efficient terahertz absorbers and highlights a novel direct writing fabrication method that can be extended to produce other optical devices for applications.

© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Electrically Tunable Goos–Hänchen Effect with Graphene in the Terahertz Regime

1. Yuancheng Fan^1,*, 
2. Nian-Hai Shen², 
3. Fuli Zhang¹, 
4. Zeyong Wei³, 
5. Hongqiang Li³,
6. Qian Zhao⁴, 
7. Quanhong Fu¹, 
8. Peng Zhang²,
9. Thomas Koschny² and
10. Costas M. Soukoulis^2,5

Version of Record online: 14 JUL 2016

DOI: 10.1002/adom.201600303

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

http://onlinelibrary.wiley.com/doi/10.1002/adom.201600303/abstract

Goos–Hänchen (G–H) effect is of great interest in the manipulation of optical beams. However, it is still fairly challenging to attain efficient controls of the G–H shift for diverse applications. Here, a mechanism to realize tunable G–H shift in the terahertz regime with electrically controllable graphene is proposed. Taking monolayer graphene covered epsilon-near-zero metamaterial as a planar model system, it is found that the G–H shifts for the orthogonal s-polarized and p-polarized terahertz beams at oblique incidence are positive and negative, respectively. The G–H shift can be modified substantially by electrically controlling the Fermi energy of the monolayer graphene. Reversely, the Fermi energy dependent G–H effect can also be used as a strategy for measuring the doping level of graphene. In addition, the G–H shifts of the system are of strong frequency-dependence at oblique angles of incidence, therefore the proposed graphene hybrid system can potentially be used for the generation of terahertz “rainbow,” a flat analog of the dispersive prism in optics. The proposed scheme of hybrid system involving graphene for dynamic control of G–H shift will have potential applications in the manipulation of terahertz waves.

Abstract-Tunable terahertz coherent perfect absorption in a monolayer graphene

Yuancheng Fan, Fuli Zhang, Qian Zhao, Zeyong Wei, and Hongqiang Li  »View Author Affiliations

Optics Letters, Vol. 39, Issue 21, pp. 6269-6272 (2014)

http://dx.doi.org/10.1364/OL.39.006269

http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-39-21-6269

Coherent perfect absorber (CPA) was proposed as the time-reversed counterpart to laser: a resonator containing lossy medium instead of gain medium can absorb the coherent optical fields completely. Here, we exploit a monolayer graphene to realize the CPA in a nonresonant manner. It is found that quasi-CPA point exists in the terahertz regime for suspending monolayer graphene, and the CPA can be implemented with the assistance of proper phase modulation among two incident beams at the quasi-CPA frequencies. The graphene-based CPA is found of broadband angular selectivity: CPA point splits into two frequency bands for the orthogonal s and p polarizations at oblique incidence, and the two bands cover a wide frequency range starting from zero frequency. Furthermore, the coherent absorption can be tuned substantially by varying the gate-controlled Fermi energy. The findings of CPA with nonresonant graphene sheet can be generalized for potential applications in terahertz/infrared detections and signal processing with two-dimensional optoelectronic materials.

© 2014 Optical Society of America

Abstract-Hyperbolic metamaterial based on anisotropic Mie-type resonance

   

 
                                                
Chuwen Lan, Ke Bi, Bo Li, Xiaohan Cui, Ji Zhou, and Qian Zhao  »View Author Affiliations

 http://www.opticsinfobase.org/DirectPDFAccess/39485C48-C2C1-9228-2B4472D09D9DE1EE_274791/oe-21-24-29592.pdf?da=1&id=274791&seq=0&mobile=yes
A hyperbolic metamaterial (MM) based on anisotropic Mie-type resonance is theoretically and experimentally demonstrated in microwave range. Based on the shape-dependent Mie-type resonance, metamaterials with indefinite permeability or permittivity parameters are designed by tailoring the isotropic particle into an anisotropic one. The flat lens consisting of anisotropic dielectric resonators has been designed, fabricated and tested. The experimental observation of refocusing and a plane wave with ominidirectional radiation directly verify the predicted properties, which confirm the potential application in negative index material and superlens. This work will also help to develop all-dielectric anisotropic MM devices such as 3D spatial power combination, cloak, and electromagnetic wave converter, etc.