  The emerging field of spinoptronics has a potential to supersede the
functionality of modern electronics, while a proper description of strong
light-matter coupling pose the most intriguing questions from both fundamental
scientific and technological perspectives. In this paper we address a highly
relevant issue for such a development. We theoretically explore spin dynamics
on the surface of a 3D topological insulator (TI) irradiated with an
off-resonant high-frequency electromagnetic wave. The strong coupling between
electrons and the electromagnetic wave drastically modifies the spin properties
of TI. The effects of irradiation are shown to result in anisotropy of electron
energy spectrum near the Dirac point and suppression of spin current and are
investigated in detail in this work.
