Chiral and Topological Surface Waves and Line Waves on Metasurfaces

The use of symmetry in electromagnetic structures provides a degree of freedom that is increasingly exploited to manipulate wave propagation. The recently discovered line waves occur at the one-dimensional interface between complementary metallic screens. A band gap can also be introduced by pairing the structure with its inverse. These materials provide unidirectional propagation in simple printed metallic patterns. Other patterns take advantage of the valley degree of freedom to produce similar effects. At optical frequencies, non-metallic structures can be produced with simple arrangements of holes in a dielectric substrate. Topological interface modes are created by manipulating the geometry to produce band inversion, or through a range of other methods such as the use of glide symmetry. A variety of techniques for designing topological structures in periodic and quasiperiodic lattices will be discussed.