Study On The Absorbing And Asymmetric Transmission Devices Based On Metamaterials

Metamaterials,a special material constructed by using artificial structures as functional units,can introduce electrical and magnetic responses to spatial changes,and achieve different functions by designing different structures.They can be designed into different structures to perform different functions,greatly expanding the design space of functional components.Optical absorber is a component that absorbs a specific wavelength band and reduces the transmission and reflection of electromagnetic waves.And asymmetric optical transmission device refers to a unidirectional device in which light can be transmitted through the device in the forward direction but cannot be transmitted in the reverse direction.As important components in all-optical devices,absorbers and asymmetric transmission device based on metamaterials have important research significance in the fields of optical communication and quantum computing,etc.In this thesis,metamaterial absorber and asymmetric transmission device are mainly studied.Firstly,we design an all-dielectric absorbing device based on indium tin oxide to achieve dual broadband absorption Secondly,we propose an all-metal asymmetric grating asymmetric transmission device to achieve narrow-band asymmetric transmission.For the metamaterial dual-broadband absorbing device,we design an all-dielectric metamaterial structure based on indium tin oxide.We conduct a series of simulation studies based on the finite-difference time-domain method.We discuss the absorbing performance under different structural parameters and the equivalent impedance of the overall absorbing structure.The results show that the metamaterial absorber can achieve excellent absorption and polarization independence in two broadband wavelength ranges,which range from 4.4 ?m to 7.8 ?m and from 9.8 ?m to 13 ?m,respectively.The device can be used as an ideal integrated absorber.This work provides a new idea for designing multi-broadband absorbers.In addition,we propose a narrow-band and high-contrast asymmetric transmission device based on metal-metal-metal(MMM)asymmetric grating structure.With the optimal design of the forward and backward grating structure parameters,the unidirectional excitation of surface plasmons polaritons(SPP),efficient tunneling,and direct decoupling of SPP,the designed asymmetric transmission device exhibits high forward transmission,near-zero backward transmission,high asymmetric transmission contrast,and high figure of merit.Numerical simulation results demonstrate that high-performance asymmetric transmission with high-quality factor(Q?91),narrow-bandwidth(6.7 nm)and high contrast ratio is achieved,with forward transmittance of 0.72 and backward transmittance of 0.0015 at visible light(610 nm).Our work provides an alternative and simple way to high-performance asymmetric transmission devices.