Pancharatnam–Berry metasurface for terahertz wave radar cross section reduction

The digital coding metasurfaces need several kinds of meta-particle structures to obtain corresponding electromagnetic wave responses and require time-consuming optimization.In this paper, we present train-symbol-shaped meta-particles with various orientations utilizing Pancharatnam-Berry(PB) phase to achieve 1-, 2-, and 3-bit digital coding metasurfaces.Terahertz wave scattering patterns of the coding metasurfaces with regular and random sequences are given and discussed.They have strongly suppressed backward scattering with approximately-13.5 dB radar cross section(RCS) reduction in a wide band range from 0.85 THz to 1.6 THz.The proposed digital coding metasurfaces provide a simple way and new opportunities for manipulating terahertz wave scattering with polarization independence.

Experimental Realization of Perfect Discrimination for Two Unitary Operations

We experimentally demonstrate perfect discrimination between two unitary operations by using the sequential scheme proposed by Duan et al.[Phys. Rev. Lett. 98 （2007） 100503] Also, we show how to understand the scheme and to calculate the parameters for two-dimensional operations in the picture of the Bloch sphere.

Wideband switchable dual-functional terahertz polarization converter based on vanadium dioxide-assisted metasurface

The terahertz technology has attracted considerable attention because of its potential applications in various fields.However,the research of functional devices,including polarization converters,remains a major demand for practical applications.In this work,a reflective dual-functional terahertz metadevice is presented,which combines two different polarization conversions through using a switchable metasurface.Different functions can be achieved because of the insulator-to-metal transition of vanadium dioxide(VO_(2)).At room temperature,the metadevice can be regarded as a linear-to-linear polarization convertor containing a gold circular split-ring resonator(CSRR),first polyimide(PI)spacer,continuous VO_(2) film,second PI spacer,and gold substrate.The converter possesses a polarization conversion ratio higher than 0.9 and a bandwidth ratio of 81%in a range from 0.912 THz to 2.146 THz.When the temperature is above the insulator-to-metal transition temperature(approximately 68℃)and VO_(2) becomes a metal,the metasurface transforms into a wideband linear-to-circular polarization converter composed of the gold CSRR,first PI layer,and continuous VO_(2) film.The ellipticity is close to-1,while the axis ratio is lower than 3 dB in a range of 1.07 THz-1.67 THz.The metadevice also achieves a large angle tolerance and large manufacturing tolerance.

Switchable vortex beam polarization state terahertz multi-layer metasurface

We propose a switchable vortex beam polarization state terahertz multi-layer metasurface,which consists of threelayer elliptical metal crosses,four-layer dielectrics,and two-layer hollow metal circles,which are alternately superimposed.Under the normal incidence of left-handed circularly polarized(LCP)wave and the right-handed circularly polarized(RCP)waves,the proposed structure realizes three independent control functions,i.e.,focused and vortex beam,vortex beam with different topological charges,and polarization states switching,and azimuth switching of two vortex beams with different polarization states.The results show that the proposed metasurface provides a new idea for investigating the multifunctional terahertz wave modulation devices.

Graphene-metasurface for wide-incident-angle terahertz absorption

We demonstrate a graphene-metasurface structure for tunable wide-incident-angle terahertz wave absorption,which involves depositing planar arrays of Omega-shaped graphene patterns on a silicon dioxide substrate.We also discuss how the graphene Fermi-level layer and various substrates affect the absorption characteristics.The absorption of the proposed terahertz absorber is above 80%at an incident angle of 0°–60°in frequencies ranging from 0.82 to 2.0 THz.Our results will be very beneficial in the application of terahertz wave communications and biomedical imaging/sensing systems.