Light transmission through a subwavelength slit: Waveguiding and optical vortices

The anomalous (i.e., more than 100%) light transmission through a subwavelength slit in a thin metal plate is accompanied by a combination of waveguiding and phase singularities of the field of power flow near the slit. The crucial role of these phase singularities (such as optical vortices and saddle points) in exciting the waveguide modes is systematically studied. We predict transmission efficiencies as high as 300% for certain configurations.