Abstract
Compared with natural materials, chiral metamaterials have been demonstrated with orders of magnitude stronger chiroptical response, which provides the basis for applications such as ultracompact polarization components and plasmonic-enhanced biosensing. Terahertz chiral metamaterials that allow dynamic polarization control of terahertz waves are of great practical interest, but remain extremely rare. Here, we show that hybrid metamaterials integrated with vanadium dioxide (VO2) exhibiting phase transition can enable dynamically tunable chiroptical responses at terahertz frequencies. In particular, a circular dichroism of ~40° and a maximum polarization rotation of ~200°/λ are observed around 0.7 THz. Furthermore, our study also reveals that the chiroptical response from the proposed metamaterials is strongly dependent on the phase transition of VO2, leading to actively controllable polarization states of the transmitted terahertz waves. This work paves the way for the development of terahertz metadevices capable of enabling active polarization manipulation.
Highlights
Since the two enantiomers of chiral objects exhibit identical scalar physical properties, remotely sensing the chiroptical response of an object provides a unique approach to enantioselectivity due to the fact that circularly polarized light (CPL) itself is chiral
Following the general design strategy, i.e., structures lacking mirror symmetry may lead to chirality, metamaterials composed of various chiral meta-atoms have been demonstrated to exhibit chiroptical responses orders of magnitude stronger than those found in natural media
Et al, have reported electrical signal controlled spatial gradient tuning in a THz metamaterial consisting of an array of split ring resonators (SRRs) located on a VO2 layer[34]
Summary
Terahertz (THz) metamaterials, especially those endowed with tunability[29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47], have proven to be highly effective in manipulating THz radiation in ways that are far superior to other natural media and offer a tremendous potential for the creation of new and transformative THz devices. Photocarrier excitation enabled dynamic control of chirality has been reported in semiconductor based active THz metamaterials. Zhang and coauthors have reported the handedness switching in three-dimensional THz chiral metamaterials in response to an external optical stimulus[36]. THz metamaterials capable of producing strong chiroptical responses that can be dynamically tuned over a large scale are highly sought after. With VO2 in its metallic state, simulation results reveal a circular dichroism of ∼40° in the absolute value and a maximum polarization rotation of ∼200°/λ around 0.7 THz. we report highly-tunable chiroptical responses that are enabled by the VO2 phase transition. Given the intensively studied phase-transition dynamics of VO2, we envision applications of the proposed hybrid metamaterials for ultrafast terahertz metadevices, such as circular polarizers and polarization modulators
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