Research On Terahertz Controllable Absorber Based On Graphene Metamaterials

With its superior characteristics,terahertz waves have shown attractive development potential in the fields of military stealth,confidential communications and disease inspections,and have stimulated the enthusiasm of various countries to develop terahertz technology.One of the difficulties in developing terahertz technology is the lack of terahertz functional devices.The lack of terahertz functional devices is mainly due to the difficulty of electromagnetic induction between natural materials and terahertz waves.The artificial metamaterials have promoted the development of terahertz functional devices to a certain extent.Even so,how to design controllable functional devices to adapt to the changing environment is still a challenge.At present,most researches are conducted from the perspective of theoretical analysis,and few researches are conducted from the perspective of applied analysis.Aiming at the same problem,we proceeded from the application point of view,based on the excellent photoelectric performance of metamaterial technology and the strong controllability of graphene,and simulated them with the finite element method,thereby designing absorbers with controllable amplitude.The specific research work includes the following three items:1.It is proposed to apply the absorber to the digital coding.Design absorbers consisting of a gold-graphene ring layer,a silicon dioxide layer and a gold reflective layer.Among them,a gold ring structure is used to achieve broadband absorption,and the Fermi level of graphene is adjusted to achieve adjustable absorption.In addition,an encoding method is proposed,which is based on the bias voltage applied to graphene to flexibly control the absorption response at terahertz frequencies,thereby having 4-element and 16-element programmable functions.The programmable broadband adjustable absorber proposed in this work has good reference values in the realization of smart devices and information storage.2.It is proposed to apply the absorber to the direct transmission of digital signals.Design an absorber composed of a graphene disc combination layer,a magnesium difluoride layer and a gold reflective layer.The absorption function is switched by controlling the voltage of the graphene.Then encode different voltage information to realize the functions of information encryption and direct transmission of digital signals.This kind of terahertz absorber,which provides multiple functions and supports digital encoding,has a good reference value in simplifying the communication process and communication security.3.It is proposed to apply the absorber to the dynamically controllable optical frequency comb.Design an absorber composed of a graphene array layer,a magnesium difluoride layer and a gold reflective layer.Use graphene arrays to achieve perfect multi-frequency absorption.By changing the Fermi level shift resonance frequencies of graphene,dynamic changes in tooth pitch and number of teeth can be achieved.This has advanced application prospects in precise ranging,long-distance communication and optical clocks.The design method and application method of the absorber proposed in the research work of this thesis can directly provide reference for the corresponding experimental work and engineering design work to realize the controllable operation of the terahertz wave amplitude.