  Recent experiments showed that the surface of a three dimensional topological
insulator develops gaps in the Floquet-Bloch band spectrum when illuminated
with a circularly polarized laser. These Floquet-Bloch bands are characterized
by non-trivial Chern numbers which only depend on the helicity of the
polarization of the radiation field. Here we propose a setup consisting of a
pair of counter-rotating lasers, and show that one-dimensional chiral states
emerge at the interface between the two lasers. These interface states turn out
to be spin-polarized and may trigger interesting applications in the field of
optoelectronics and spintronics.
