  We investigate transport properties through nano-ribbons of thin topological
insulators irradiated by high frequency light with circular polarization. By
using high frequency regime, a coherent and quantized transport through the
nano-ribbon is guaranteed and then Lanadauer formalism is applicable. It is
demonstrated that the pseudo-spin edge modes inside the band gap can host
transmission through this nano-junction which their localization on the top and
bottom edges depend strongly on the light polarization. These edge modes
persist even if we apply a source-drain bias. Based on this edge selectivity
for the current, one can design a light-induced switch with an appropriate
on/off ratio of the current which is composed of two scattering regions with
opposite light polarization. The local current on each bond shows how the
current is passing through the edges and jumps into the opposite edge.
Furthermore, some other nano-junctions are proposed as electronic switches
which are designed based on the mass term engineering of the scattering region
by means of perpendicular magnetization induced by magnetic doping and also
structure inversion asymmetry applied on the scattering region.
