Design And Simulation Of Tunable Terahertz Metamaterial Absorber

Metamaterial is a new kind of composite material with periodic structure.Due to the fact that its equivalent permittivity and permeability can be designed,it shows the surprising electromagnetic properties and has been widely concerned by researchers.In lack of effective terahertz wave sources and detectors,the research on terahertz wave lags behind the other bands and it was known as the terahertz gap.The metamaterial is designed to be able to respond to terahertz waves.Therefore,the study of metamaterials plays an important role in the research on terahertz wave.The metamaterial absorber was first proposed in 2008 by N.I.Landy et al.It demonstrates excellent advantages such as perfect absorption of electromagnetic waves with certain frequency,narrow absorption peak for frequency selection,flexible design and thin thickness.With continuous development,some new characteristics,such as wide incidence angle,polarization insensitivity and broadband operation,have been successfully obtained.In this paper,two kinds of terahertz tunable metamaterial absorbers are proposed,designed and simulated by COMSOL software.The main work is as follows:(1)A new modulation method is proposed.The air cavity with periodic arrangement is designed.Through introducing external pressure into the cavity,the flexible PDMS membrane covering the air cavity will be deflected upward or downward.The geometrical parameters of the metamaterial structure sitting on the membrane will be changed,thus modulating its absorption performance.(2)Based on the new modulation method,two kinds of metamaterials are designed in this paper.They are symmetric rectangular strip structure and symmetric open ring structure.These two kinds of structures are simulated by using parametric scanning in COMSOL to get optimized structure design.Their equivalent circuit models are obtained according to the field distribution,and the relationship between the resonance frequency and the geometric parameters is studied.Finally,the frequency tuning is analyzed.