Dual-channel optical switch, refractive index sensor and slow light device based on a graphene metasurface

Abstract

In this paper, we propose a graphene-based metasurface that exhibits multifunctions including tunable filter and slow-light which result from surface plasmon polaritons (SPPs) of graphene and plasmon induced transparency (PIT), respectively. The proposed metasurface is composed by two pairs of graphene nano-rings and a graphene nanoribbon. Each group of graphene rings is separately placed on both sides of the graphene nanoribbon. Adjusting the working state of the nanoribbon can realize the functional conversion of the proposed multifunctional metasurface. After that, in the state of two narrow filters, we put forward the application concept of dual-channel optical switch. Using phase modulation of PIT and flexible Fermi level of graphene, we can achieve tunable slow light. In addition, the result shows that the graphene-based metasurface as a refractive index sensor can achieve a sensitivity of 13670 nm/RIU in terahertz range. These results enable the proposed device to be widely applied in tunable optical switches, slow light, and sensors.

Metasurface Based on Inverse Design for Maximizing Solar Spectral Absorption

“…Figure 4g shows the simulated absorptive spectrum with different radius of the single‐layer TiN cylinder grating. According to the Mie resonance theory, [ 10–39 ] the Mie resonance depends only on size parameter q is proportional to the ratio between the nanoparticle radius R and the wavelength of light λ ( q = 2 πR /λ). As the radius ( r 1 ) increase, the first mode of the Mie resonance redshifts and relates to parameter of r 1 .…”

“…In the theoretical analysis process of forward designs, researchers often give theoretical analyses of coupled mode theory, transmission line theory, and hybridization model to simplify the solution of Maxwell's equations. [10,37,[40][41][42] Generally, inverse design aims at the analysis of spectral characteristics. This is because in some problems spectral characteristics are directly related to the application with ideal spectral curves, including but not limited to sunlight absorption, radiative cooling, nanophotonic devices, and multispectral camouflage problems.…”

“…As shown in Figure a, in the traditional design process, most researches obtain the initial structure through a priori method, including but not limited patterned structure (topological structure), multilayer structure, and stage structure, and then manually select the initial structure. [ 10,38,39 ] The purpose of designing these structures is to obtain a better spectral response, such as absorption spectrum, transmission spectrum, and reflection spectrum. At first, the structures that can be considered as the independent variable are initially designed.…”

“…[ 7 ] proposed metasurface‐based perfect absorber (PA) for the first time, the considerable designs for the metasurface‐based PAs with different patterns and materials open up the opportunity for narrow‐band absorption, broadband absorption, and tunable absorption in some spectral wavelength range. [ 9–14 ]…”

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absorption in some spectral wavelength range. [9][10][11][12][13][14] Broadband absorption of sunlight is key for solar cell technologies, so metasurface-based structure has emerged as a promising technique for their efficiency improvement. [15][16][17] It is widely used in photothermal energy generation, [18,19] thermal emitters, [20] and detectors [21] to combine the metasurface-based PAs like a blackbody with the broadband absorption of sunlight.

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