Abstract
The influences of intense coherent laser fields on the transport properties of a single-layer graphene are investigated by solving the time-dependent Dirac equation numerically. Under an intense laser field, the valence band and conduction band states mix via the optical Stark effect. The chiral symmetry of Dirac electrons is broken and the perfect chiral tunneling is strongly suppressed. These properties might be useful in the fabrication of an optically controlled field-effect transistor.