  We discuss optical absorption in topological insulators and study possible
photoelectric effects theoretically. We found that absorption of circularly
polarized electromagnetic waves in two-dimensional topological insulators
results in electric current in the conducting 1D edge channels, the direction
of the current being determined by the light polarization. We suggest two ways
of inducing such a current: due to magnetic dipole electron transitions
stimulated by irradiation of frequency below the bulk energy gap, and due to
electric dipole transitions in the bulk at frequencies larger than the energy
gap with subsequent capture of the photogenerated carriers on conducting edge
states.
