Optically tunable terahertz chiral metasurface based on multi-layered graphene

Abstract

Active manipulation of the polarization states at terahertz frequencies is crucially helpful for polarization-sensitive spectroscopy, having significant applications such as non-contact Hall measurements, vibrational circular dichroism measurements and anisotropy imaging. the weakness of polarization manipulation provided by natural materials can be overcomed by chiral metamaterials. Chiral metamaterials have a huge potential to achieve the necessary polarization effects, hence they provide the basis for applications such as ultracompact polarization components. terahertz chiral metamaterials that allow dynamic polarization modulation of terahertz waves are of great practical interest and still challenging. Here, we show that terahertz metasurface based on the four conjugated "petal" resonators integrated with multi-layered graphene (MLG) can enable dynamically tunable chiroptical response using optical pumping. In particular, a change of ellipticity angle of 20° is observed around 0.76 THz under optical pumping by a 980 nm continuous wave (CW) laser. Furthermore, using temporal coupled-mode theory, our study also reveals that the chiroptical response of the proposed multi-layered graphene-based metasurface is strongly dependent on the influence of optical pumping on the loss parameters of resonance modes, leading to actively controllable polarization states of the transmitted terahertz waves. the present work paves the way for the realization of fundamental terahertz components capable for active polarization manipulation.

Dynamic Control of Light Chirality with Nanostructured Monolayer Black Phosphorus for Broadband Terahertz Applications

“…[19][20][21][22][23][24][25][26] Systems utilizing graphene could potentially provide the necessary functionalities. However, to achieve polarization conversion, symmetry breaking has to be introduced; this can be implemented geometrically, [15,[27][28][29] e.g., via patterned nanorectangles, [15] or by inducing anisotropy in the graphene conductivity, e.g., through the application of strong magnetic fields. [30] Alternatively, the tunable anisotropic conductivity of monolayer black phosphorus (BP), a 2D material with an inherent anisotropic crystalline structure, [24,31,32] can circumvent the above limitations, offering the desired tunability and wideband operation within the same system.…”

Chiral Graphene Hybrid Materials: Structures, Properties, and Chiral Applications

“…prepared terahertz chiral metamaterials with polarization manipulation ability, which is constructed by multilayered graphene. [ 316 ] Hu et al. theoretically demonstrated that CD effects can be enhanced in chiral hybrid metamaterials composed of graphene and chiral metal nanocrystals at near‐infrared region.…”

Graphene-based dual-functional chiral metamirror composed of complementary 90° rotated U-shaped resonator arrays and its equivalent circuit model

“…Chiral metastructures are applicable platforms due to their chirality responses such as circular dichroism (CD) 1 and/or linear dichroism (LD) 2 in the terahertz (THz) region. Graphene-based chiral metastructures have been designed and developed recently to achieve tunable CD and/or LD chirality responses 1 – 6 . Graphene, 2D layer of graphite, with a thickness of 0.335 nm 7 , has become a promising material in electromagnetics and optoelectronics metastructures as it is capable of dynamically tuning electromagnetic waves 3 – 9 .…”