Gate-tuned graphene meta-devices for dynamically controlling terahertz wavefronts

Abstract

Dynamical controls on terahertz (THz) wavefronts are crucial for many applications, but available mechanism requests tunable elements with sub-micrometer sizes that are difficult to find in the THz regime. Here, different from the local-tuning mechanism, we propose an alternative approach to construct wavefront-control meta-devices combining specifically designed metasurfaces and globally tuned graphene layers. Coupled-mode-theory (CMT) analyses reveal that graphene serves as a tunable loss to drive the whole meta-device to transit from one functional phase to another passing through an intermediate regime, exhibiting distinct far-field (FF) reflection wavefronts. As a proof of concept, we design/fabricate a graphene meta-device and experimentally demonstrate that it can reflect normally incident THz wave to pre-designed directions with different polarizations under appropriate gating voltages. We finally design a graphene meta-device and numerically demonstrate that it can generate vectorial THz beams with continuously varying polarization distributions upon gating. These findings pave the road to realizing a wide range of THz applications, such as sensing, imaging, and wireless communications.

Optical properties and polaritons of low symmetry 2D materials

“…Thus, anisotropic 2D materials benefit from the common merits of 2D materials, such as strong light-matter interaction and high tunability, and at the same time, with additional anisotropy, are expected to show much richer physics, which is very promising for basic research and practical applications in photonics and optoelectronics. In fact, optical anisotropy can be found in in-plane isotropic 2D materials with anisotropic nanostructures as well [15,32,33] . However, it should be noted there is an essential difference between low symmetry 2D materials and symmetric 2D materials with anisotropic nanostructures.…”

Optically controlled dielectric metasurfaces for dynamic dual-mode modulation on terahertz waves

“…Metasurfaces, ultrathin metamaterials constructed by planar microstructures exhibiting tailored electromagnetic responses, provide a powerful platform to manipulate light at the deep-subwavelength scale 1 – 7 Combining passive metasurfaces with different external-stimuli-controlled materials (e.g., semiconductors, 8 – 11 2D materials, 12 – 15 phase-change materials, 16 – 21 PIN diodes, 22 elastic materials, 23 microfluidic materials, 24 mechanical devices, 25 , 26 and liquid crystals 27 – 30 ), many tunable metadevices were successfully constructed, which can dynamically control THz waves by applying different external stimuli 31 . Among these attempts, optically controlled metadevices 32 – 35 have gained intensive attention due to their attractive properties, including ultrafast modulation speed and high modulation pixel resolution.…”

Effects of propagation phase on the coupling of plasmonic optical modes

“…Another development path is to keep the mode simple, while consider complicated source and detection (port) like oblique incident light sources [25,26] and detection with different polarizations (polarization conversion) [27] . In recent years, TCMT has been further generalized [28][29][30][31][32][33][34] . For example, in 2021 Alu's research group used TCMT to explain the thermal metasurface of the combined local and nonlocal light-matter interaction [25] .…”