Study Of Tunable Terahertz Metamaterial Absorber

Metamaterials,consisting of new-fashioned man-made periodic subwavelength structure,can exhibit a number of extraordinary electromagnetic characteristics.In recent years,the application of metamaterials in terahertz spectrum has attracted growing attention due to the relatively big challenges associated with conventional technology.Among various metamaterial applications,the terahertz metamaterial absorber,which plays an important role in THz area,has currently provoked comprehensive interest owing to its flexible design,ultra-thin structure and high absorption.Different from the traditional absorber,whose absorption resonance is dominated by inherent complex permittivity and permeability of the bulk material,the metamaterial absorber can be flexibly designed to achieve absorption resonance for different spectral ranges by tailoring the geometry of the periodic structures.While terahertz metamaterial absorbers have a number of merits,their absorption performance can hardly be tuned due to their as-fabricated structure geometry.Until now,a lot of tuning strategies have been proposed,but most of them cannot be easily achieved.Therefore,it is necessary to explore a new design strategy for tunable THz metamaterial absorber to provide a more integrated and convenient tuning capability.In this paper,four kinds of tunable composite metamaterial structure based on our previously developed pneumatic actuation mechanism are proposed,due to their easy fabrication and compact integration advantages.In these tunable absorber structures,particularly designed metal structure and a pneumatic actuator are integrated together to provide different absorption modulation capability.Metal structure,which is designed into two concentric patterns,is arranged onto the surface of the suspending membrane of the pneumatic actuator to construct the proposed metamaterial together with a metal ground plane and the air gap between them.During operation,the geometric parameters of the metal structure can be dynamically adjusted through controlling the applied pressure,leading to the tuning on the absorption peaks.In order to study the mechanical and electromagnetic performance of those proposed tunable terahertz metamaterial absorbers and verify their tunability,simulations using COMSOL Multiphysics are performed,including mechanical and electromagnetic.To explore the resonant absorption mechanism,the absorption characteristics of current metamaterial absorber as well as the corresponding electric field distribution at individual resonant frequencies under different pneumatic actuation statuses have been studied.