Control of light polarization in structured cavities by a magnetic field

We demonstrate that the polarization of the optical modes in wirelike microcavities formed by lithography can be controlled by an external magnetic field, At zero field, these modes are split into two linearly polarized components by the resonator geometry with a splitting which depends on the wire width and the mode index. A magnetic field causes these modes to become circularly polarized and their splittings to increase. These effects are shown to result from magnetic-field dependence of the dielectric function.