Topological valley plasmon transport in bilayer graphene metasurfaces for sensing applications

Abstract

Topologically protected plasmonic modes located inside topological bandgaps are attracting increasing attention, chiefly due to their robustness against disorder-induced backscattering. Here, we introduce a bilayer graphene metasurface that possesses plasmonic topological valley interface modes when the mirror symmetry of the metasurface is broken by horizontally shifting the lattice of holes of the top layer of the two freestanding graphene layers in opposite directions. In this configuration, light propagation along the domain-wall interface of the bilayer graphene metasurface shows unidirectional features. Moreover, we have designed a molecular sensor based on the topological properties of this metasurface using the fact that the Fermi energy of graphene varies upon chemical doping. This effect induces strong variation of the transmission of the topological guided modes, which can be employed as the underlying working principle of gas sensing devices. Our work opens up new ways of developing robust integrated plasmonic devices for molecular sensing.

Second-harmonic generation via double topological valley-Hall kink modes in all-dielectric photonic crystals

“…4(a) by dots and the blue (dark gray) line, respectively (see [45] for further details). While the fundamental wave atk f is launched unidirectionally rightward (the source is marked by the arrow) [46,47], from the field of |E 2 |, one can see that, indeed, both forward-and backward-propagating waves are generated.…”

Topological Valley Photonics: Physics and Device Applications

“…Recently, topological valley plasmonic crystals for manipulating surface plasmons (including graphene plasmons) have also been theoretically studied. [ 19,111–113 ] In addition, there have been some works discussing tunable VPCs, opening a door toward dynamically reconfigurable topological nanophotonic devices. [ 111,114–116 ]…”

Nonlinear optical interactions of topological modes of photonic nanostructures

“…A complication in the current all-dielectric PhC structure stems from the fact that, as the system has time-reversal symmetry, at each frequency there are two kink modes (corresponding to the two valleys at K and K ) for both the fundamental and the second-harmonic components. Although one can excite the fundamental wave unidirectionally exploiting the inherent chirality of the kink modes, e.g., by using sources of either right-or left-circularly polarized light, 25,26 generally the generated second-harmonic waves will have both forward-and backward-propagating components. A typical example is shown in Fig.…”

“…24 Until recently, valley-Hall photonic modes have been mostly studied in bulk materials, being less explored in 2D photonic platforms, including graphene. 25,26 This 2D material is becoming a promising platform to achieve passive and active topologically protected plasmonic modes, [27][28][29] due to its high carrier mobility and long relaxation time. 30,31 This invited paper is organized as follows.…”