Study Of Controllable Terahertz Metamaterials Based On Vanadium Dioxide And Their Chiral Properties

Metamaterials is a newborn platform to realize electromagnetic functional devices,the development of novel controllable metamaterials will further promote and expand the research and application of multifunctional modulators.In particular,metamaterials with chiral property can load more electromagnetic information through polarization.In this thesis,polarization property(chiral correlation)and dispersion(plasmon-induced transparency,PIT)property of THz metamaterials are systematically studied.1.Two dimensional achiral metamaterials with different degrees of symmetry have been realized,accompanied with their active and passive modulation.Combining conventional reflector with two-dimensional achiral metamaterials which exhibits different degrees of symmetry to realize perfect absorber,wide-band handedness preserving reflector,and band-blocking handedness preserving reflector,respectively;the symmetry degree influence of two dimensional achiral metamaterials on their electromagnetic response has been systematically summarized;electromagnetic response of the proposed metamaterials was passively modulated by tailoring the geometry of the microstructure;introducing vanadium dioxide(VO₂)functional materials to construct Au/VO₂ hybrid metamaterials,and realizing switchable wide-band and band-blocking handedness preserving mirrors.2.Two-dimensional chiral metamaterials and its active modulation have been realized.Combining two-dimensional chiral metamaterials with conventional mirror to construct a chiral mirror;temperature-controlled two-dimensional chirality and circular polarization conversion dichroism has been realized by using Au/VO₂two-dimensional chiral metamaterials;combing the above Au/VO₂ two-dimensional chiral metamaterials with conventional mirrors to realize three types of switchable chiral mirrors,which can be switched between conventional mirror,handedness preserving mirror,and chiral mirror.3.Three-dimensional chiral metamaterials and its active modulation has been realized.Employing anisotropic Al/VO₂ three-dimensional chiral metamaterials to realize temperature-controlled three-dimensional chirality,optical activity,linear polarization conversion and linear polarization asymmetric transmission.Exploiting isotropic Au/VO₂ three-dimensional chiral metamaterials with four-fold rotational symmetry to realize temperature-controlled circular dichroism,circular birefringence,linear polarization conversion,and negative refractive index.4.High-efficiency two-dimensional chiral metamaterials and their practical applications have been realized.Using two-dimensional chiral silicon metamaterials with two-fold rotational symmetry,to realize the high-efficiency asymmetric transmission of circularly polarized THz wave,which breaks the asymmetric limit of metallic two-dimensional chiral metamaterials;by introducing geometric phase technology,the chirality-switched dual-band diffraction grating has been realized;chirality-switched holographic imaging metamaterial has been realized by integrating silicon metamaterials with holographic iterative algorithms,which exhibits a polarization-switched image at two separating frequencies.5.Single transparency window and double transparency window PIT metamaterials have been realized,accompanied with their active and passive modulation.Constructing a three-level THz metamaterial with bright-bright mode coupling to realize the single transparency window PIT phenomenon;passive modulation and robust PIT metamaterials have been realized by modifying the relative arrangement of microstructures;polarization independent/switched PIT effect has been realized by constructing the PIT metamaterials with mirror symmetry and four/two-fold rotational symmetry simultaneously.Constructing a four-level THz metamaterial with bright-asymmetric dark mode coupling to realize the double transparency window PIT phenomenon.Passive modulation of double transparent window PIT effect has been realized by changing the relative arrangement of dark mode.Temperature-controlled PIT metamaterials were realized by introducing VO₂ film in the above metallic metamaterials.