Abstract-Active metasurface devices for terahertz wave front modulation

Yan Zhang, Jingying Guo, Teng Wang, and Xinke Wang

https://www.osapublishing.org/abstract.cfm?uri=CLEO_Europe-2019-cc_p_8

Terahertz (THz) radiation, which is sandwiched between the infrared and microwave in the electromagnetic spectrum, has become more and more attractive due to its special properties. Compared with the quick development of THz sources and detectors, THz functional devices are lagging behind, especially the devices for wave front modulation. Metasurface, a kind of artificial materials, is enable effective manipulation of the amplitude, phase and polarization state of electromagnetic waves with subwavelength spatial resolution. It has been used for ultrathin planar lenses, complex light field generation, spin orbital angular momentum coupling, and metasurface holograms. However, the function of this kind of metasurface based devices are fixed once they are fabricated, the spatial THz modulation which can dynamically modulate the wave front of THz radiation is demand in high resolution THz imaging and THz communication.

© 2019 IEEEhttps://www.osapublishing.org/abstract.cfm?uri=CLEO_Europe-2019-cc_p_8

Abstract-Thermally switchable terahertz wavefront metasurface modulators based on the insulator-to-metal transition of vanadium dioxide

Teng Wang, Jinwen He, Jinying Guo, Xinke Wang, Shengfei Feng, Florian Kuhl, Martin Becker, Angelika Polity, Peter J. Klar, and Yan Zhang

Fig. 1 Schematic image of the setup used for studying operational characteristics of the THz wavefront modulators as a function of temperature. (a) The device has no effect on the THz wave in its off-state (e.g., at T = 20 °C < TC). The THz device acts on the THz wave in its on-state (e.g., at T = 70 °C > TC) as (b) a multiple foci lens or (c) a Ariy beam generator. TTML: Temperature controlled THz multi-focus lens. TTAG: Temperature controlled THz Ariy beam gererator.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-27-15-20347

Active use of phase transition phenomena for reversibly tuning the properties of functional materials in devices currently is an attractive research area of materials science. We designed and fabricated two kinds of metasurface modulators for dynamically controlling the wavefront of terahertz (THz) radiation based on the temperature-induced insulator-to-metal phase transition of vanadium dioxide (VO2). The modulators designed are based on the C-shaped slot antenna array. The slot antennas are made of the VO2 films on c-sapphire substrates. The C-shaped slot antennas are active only when the VO2 is in its metallic phase, i.e. at temperatures T > TC ∼68 °C. At T > TC, the first kind acts as a THz multi-focus lens which converges an incident THz plane wave into four focal spots and the second kind as an Airy beam generator. We characterized the function of two THz wavefront modulators over a broad frequency range, i.e. from 0.3 to 1.2 THz. Such thermally switchable THz wavefront metasurface modulators with a capability of dynamically steering THz fields will be of great significance for the future development of THz active devices.

© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Reconfigurable Terahertz Metasurface Pure Phase Holograms

Jinying Guo, Teng Wang,  Huan Zhao, Xinke Wang,  Shengfei Feng, Peng Han, Wenfeng Sun,   Jiasheng Ye, Guohai Situ, Hou‐Tong Chen,Yan Zhang

https://onlinelibrary.wiley.com/doi/abs/10.1002/adom.201801696?af=R

Terahertz (THz) radiation has many potential applications. However, comparing with the rapid development of THz sources and detectors, functional devices for THz modulation, especially the spatial modulation devices, are still insufficient. Here, a novel approach for generating arbitrary wavefronts of a THz beam is presented. By dynamically creating metasurface structures through illuminating a thin silicon wafer with femtosecond laser, which is spatially modulated, an array of reconfigurable subwavelength resonators is generated. The wavefront of the THz beam is then determined by forming spatial profiles of the Pancharatnam–Berry scattering phase by dynamically controlling the resonator orientation. Proof‐of‐concept experiments demonstrate that streaming holographic images and lenses of variable focal length can be realized in real time. The reconfigurable scheme demonstrated here is convenient and fast, and may lead to advances in a host of THz applications.