Abstract
Arbitrary control and dynamic tuning of circularly polarized (CP) wave are of great significance to photonic research and application. Here, a terahertz switchable metasurface is designed with bifunctional properties based on a mixed structure of graphene and vanadium dioxide (VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ). The design consists of VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> strips, topas spacer, VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> film, graphene patch, topas spacer, and metallic film. When VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> is metal, this metasurface realizes photonic spin Hall effect (PSHE) for CP wave in a wide frequency band of 0.7-1.5 THz. When VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> is insulator, the design behaves as an absorber. It has a broadband absorption with more than 90% absorptance in the range of 0.48-1.88 THz, and there are two resonant peaks with ~100% absorptance at 0.92 THz and 1.74 THz. Meanwhile, absorption bandwidth and intensity can be dynamically tuned by changing Fermi energy level of graphene. Besides, broadband absorption is robust against incident angle. Our design may promote the realization of terahertz switchable and multifunctional metasurfaces.
Highlights
T RADITIONAL methods of manipulating electromagnetic wave depend on gradually changing the phase during propagation, so the involved devices have complex and irregular shapes
photonic spin Hall effect (PSHE) is a photon analogy of Spin Hall effect (SHE), and it refers to the transverse spin splitting of optical orbit
We introduce graphene layer and add cross pattern to increase absorption
Summary
T RADITIONAL methods of manipulating electromagnetic wave depend on gradually changing the phase during propagation, so the involved devices have complex and irregular shapes. It is not in line with the current trend of integration. Metasurface as a 2D ultra-thin metamaterial integrates artificially subwavelength microstructure into an interface. Since the concept was put forward, metasurface has attracted much attention because of its extraordinary electromagnetic properties [1]–[3]. Metasurface with the subwavelength thickness can modify boundary conditions of incident waves to control amplitude, phase, polarization, and wavefront. Many interesting phenomena have been proposed, such as beam-steerers [4]–[6], photonic spin Hall effects (PSHEs) [7]–[9], focusing lenses [10]–[12], optical holograms [13]–[15], intelligent codings [16]–[18], waveplates [19]–[21], invisible cloaks [22]–[24], and so on
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