Dynamically Tunable Broadband Infrared Anomalous Refraction Based on Graphene Metasurfaces

Abstract

or wavelength of incident light. However, the anomalous refraction effi ciency is closely related to the resonance. The highest anomalous refraction effi ciency will occur at the resonant wavelength, and decrease when the wavelength of incident light is away from it. The highest conversion effi ciency has to be tuned to different wavebands by carefully reoptimizing and resizing the geometric parameters of the structures. This lacks fl exibility for active control, which limits its uses in practice.One way to realize the active control of the anomalous refraction effi ciency may be integrating metasurfaces with permittivity-tunable materials. [17][18][19] By external stimulus such as electric and/or magnetic fi eld, voltage, or temperature, the optical response of the integrated metasurfaces can be actively controlled. Graphene, which is a single 2D plane of carbon atoms arranged in a honeycomb lattice, has been demonstrated to support surface plasmon polaritons. [ 20,21 ] As its conductivity can be dynamically controlled by electrostatic gating, it seems to be a good candidate for designing tunable devices and becomes a hot material in both physics and engineering. [22][23][24][25][26] Graphene-based metamaterials have been wildly demonstrated to achieve tunable devices such as absorbers, [ 27 ] antennas, [ 28,29 ] polarization converters, [30][31][32] and transformation optical devices. [ 33 ] Recently, metasurfaces based on 1D graphene nanoribbons have been demonstrated to manipulate wavefront of light. [ 34 ] Since only the width of 1D nanoribbon is adjustable, the conductivity of the nanoribbons needs to be individually adjusted to realize the phase range covering from 0 to 2π, which is diffi cult in practical applications. However, there are more adjustable structural parameters for 2D graphene nanostructures to satisfy the phase condition. The new degrees of freedom of graphene metasurfaces may facilitate arbitrary manipulation of light wavefront by uniform conductivity and will profoundly affect a wide range of photonic applications.Here, we propose a highly tunable broadband anomalous refraction composed of periodically patterned graphene nanocrosses for circularly polarized waves in the infrared regime. We demonstrate the applicability of the scheme to generalize anomalous refraction by investigating the effect at various incident angles and different wavelengths. More importantly, the anomalous conversion effi ciency can be dynamically tuned and remain as high in a broadband frequency range by varying the Metasurfaces, which are capable of generating structure and wavelength dependent phase shift, have emerged as promising means for controlling the wavefront of electromagnetic waves. Finding new ways to realize broadband frequency response as well as maintaining high conversion effi ciency still requires research efforts. For the design of plasmonic metasurfaces, graphene represents an attractive alternative to metals due to its strong fi eld confi nement and versatile tunability. Here, a novel metasurf...

An electromagnetic modulator based on electrically controllable metamaterial analogue to electromagnetically induced transparency

“…However, the local-resonant nature of metamaterials limits its operation in a narrow frequency band. It is highly desirable to achieve frequency-agile or multi-band operating metamaterial to extend the working band of a manufactured metamaterial18192021222324252627. As part of this development, considerable interest has been focused on the realization of actively controlled metamaterials that exhibit tunable optical response for practical applications in functional optical devices.…”

Phase Manipulation of Electromagnetic Waves with Metasurfaces and Its Applications in Nanophotonics

“…[252] By introducing a phase gradient along the propagation direction of light with plasmonic or dielectric nanoantennas, an effective wavevector can be imparted to the incident mode, which can convert the higher-order waveguide mode into a lower-order mode or an SW. Currently, several methods have been proposed to realize dynamically reconfigurable metasurfaces, [255] such as electrical control, [55,153,215,256,257] optical control, [121,[258][259][260] mechanical control, [119,120] and thermal control. [253] Notably, an optical fiber, as another type of waveguide, can also be an important platform to implement phase gradient metasurfaces.…”

“…[46,47] Several strategies have also www.advopticalmat.de been demonstrated to improve the manipulation efficiency, such as introducing a reflection configuration, [48,49] plasmonic hybridization, [50] and few-layer nanoantennas. [55] Inspired by the concept of the linear P-B phase, a nonlinear metasurface allowing a continuous control of the phase of the local effective nonlinear polarizability was recently demonstrated, as illustrated in Figure 1h. [52][53][54] By implementing the P-B phase with silicon nanoantennas (Figure 1g), a highefficiency anomalous refraction metasurface operating in transmission mode can be achieved in the visible region.…”

Polarization State Manipulation of Electromagnetic Waves with Metamaterials and Its Applications in Nanophotonics

“…This tunable polarizers (or polarization switchers) provide an alternate way for the waveband controlling of polarization state manipulation. A step further, not only the waveband and functionalities of polarization state manipulation can be tuned with graphene-based metamaterials, Figure 7g shows tunable wavefront controlling of crosspolarized electromagnetic waves based on periodically paterned graphene nano-crosses in the infrared regime [60]. With this device, the wavefront of cross-polarized circular refraction waves can be efectively controlled with the polarization conversion induced geometric phase and the working waveband can be dynamically tuned (as shown in Figure 7h and i).…”