| With the pace of the times,technology is also constanttly developing.The performance requirements of absorbers are getting higher and higher.In order to meet people's demand for miniaturized and integrated absorber.Based on the extraordinary electromagnetic characteristics of micro-nano structure and structure can be simplified,integrated,nano scale characteristics.Many applications and ideas of absorbers based on micro-nano structures have been continuously proposed,especially in the fields of sensing,stealth,and imaging.Due to the fixed material parameters and resonant structure of the traditional micro-nano structure,the resonant frequency of the absorber is fixed,which cannot be effectively adjusted,thus limiting the wider application space.The emergence of the two-dimensional material graphene can solve this problem well,graphene is a two-dimensional nanomaterial in which carbon atoms are distributed in a hexagonal shape in the same plane.and its conductivity can be adjusted by the environment,such as changing the bias voltage.Through the combination of graphene and micro-nano structure,the absorption frequency can be regulated and its absorption peak can be tunable,which significantly improves the use of graphene in optoelectronic devices,such as photoelectric detectors and photovoltaic fields.At the same time,the graphene-based micro-nano structure is simple in structure and small in size,which has important application value in the design of future ultra-micro devices.This paper mainly studies the resonance mechanism and absorption characteristics of two kinds of optical microstructures absorbers with metamaterials and subwavelength gratings combined with graphene based on the finite element method.The main contents are as follows:1.Designed and numerically analyzed a tunable dual-band perfect metamaterial absorber based on a single-layer graphene array in the terahertz band.The proposed metamaterial absorber structure includes an array of porous graphene disks on top of a gold ground plate separated by a Si O2 dielectric substrate.The absorption peaks reach100% at 28 ?m and 63.7 ?m.By controlling the conductivity and structural parameters of graphene,the resonance frequency can be adjusted.In addition,the absorber is insensitive to polarization and incident angle changes.The designed structure allows the application of sensor elements with sensitivity S up to 0.67 THz/RIU and 2.33 THz/RIU,respectively.2.A broadband terahertz absorber is designed.The absorber uses unpatterned continuous graphene sheets and is placed on a one-dimensional dielectric grating supported on a metal reflector.The principle of the absorber is to use the combination of guiding mode resonance of the grating and Fabry-Perot resonance of the medium to stimulate continuous plasma resonance,so as to achieve wide band terahertz absorption.In the frequency range of 1.19-3.58 THz,the absorber achieves more than 80%absorption and the relative bandwidth reaches 100.2%.In addition,by controlling the conductivity,incident angle and polarization of graphene,the absorber also has adjustable characteristics.Since the graphene sheet is unstructured and directly attached to the surface of the dielectric layer,this design solution greatly reduces the difficulty of preparation.This broadband absorber has broad application prospects in stealth,switch and other fields.The absorber studied in this paper can achieve dual-band and broadband absorption functions,and because of the adjustable conductivity of graphene,it can be dynamically adjusted by methods such as bias voltage.The terahertz absorption device with adjustable frequency and absorption rate can be realized by using its characteristics,and has a simple structure,easy processing,and strong practicability.It provides new ideas for dual-band and broadband absorbers on micro-nano-scale absorption devices,and improves the absorption efficiency and controllability of terahertz band absorbers,which has great practical application value. |
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