Multifunctional analysis and verification of lightning-type electromagnetic metasurfaces

Abstract

Aiming at the problems that most of the existing electromagnetic metasurfaces have single function and narrow application scope, a highly integrated lightning-type metasurface is proposed in this study. It can realize the functions of circular dichroism (CD), absorption of electromagnetic waves, broadband x-to-y cross polarization conversion (CPC) function, linear-to-circular polarization conversion (LTC-PC) function and asymmetric transmission (AT), and its functions are also analyzed and verified. The designed metasurface consists of the bottom grating structure, the lower SiO2, the middle lightning-type graphene, the upper SiO2, the top graphene and photosensitive silicon. Through numerical calculations, the CD of design can reach more than 85% at 4.22 THz. The function of bimodal absorption is achieved at 4.09 and 8.69 THz. At 7.41∼8.21 THz, the polarization conversion ratio (PCR) of the metasurface reaches more than 99%. Simultaneously, the function of LTC-PC can be formed when PCR is 50%. Finally, when the designed metasurface is in the transmissive state, the AT of design is close to 60% at 7.84 THz. This design provides a new design idea and method for biomedical detection, image processing, modulators, smart switches, optical diodes and other fields.

A switchable and tunable multifunctional terahertz polarization converter based on a graphene metasurface

“…This causes LCP waves to be reflected and RCP waves to be absorbed, ultimately giving rise to CD. 12…”

“…In this context, E f for the top square graphene resonant ring is denoted as E f1 , while the middle N-type graphene layer's E f is designated as E f2 . The electrical conductivity of graphene is described using the Drude model, as expressed in eqn (2): 12 In the equation, ω is the angular frequency, μ c is the Fermi energy level, Γ is the scattering rate, k B is Boltzmann's constant, ħ is the reduced Planck constant, and e is the electronic charge. In this paper, the graphene temperature is set to T = 300 K, and the relaxation time τ = 1 ps.…”

“…This causes LCP waves to be reflected and RCP waves to be absorbed, ultimately giving rise to CD. 12 In Fig. 9(a), within the F-P cavity formed by the metasurface, the wave undergoes multiple reflections between the two graphene layers, with some light transmitted during each reflection.…”

“…For the pursuit of miniaturization and multifunctional integration of devices, the design of new switchable and tunable metasurfaces with multiple functions has become a hot research issue. 12 Tunable multifunctional metasurfaces are primarily achieved through the use of active materials such as graphene, 13 VO 2 14 and photosensitive silicon. 15 Graphene is a novel material with high electron mobility and optical transparency.…”

Plasmonic Sensing and Switches Enriched by Tailorable Multiple Fano Resonances in Rotational Misalignment Metasurfaces

“…It has been found that the optical switch that enables the signal to be turned on and off by another controller plays an important role in routing the optical signal in optical communication and information processing [ 49 ]. However, the prevailing way of optical switching usually requires an auxiliary power supply and additional control circuits that are physically connected to the metasurface, thus leading to increasing the size of the system and inducing needless cross-talk [ 50 , 51 ].…”