Creation and annihilation of phase singularities near a sub-wavelength slit.

The anomalously-high transmission of light through subwavelength apertures is a phenomenon which has been observed in numerous experiments, but whose theoretical explanation is incomplete. In this article we present a numerical analysis of the power fl ow (characterized by the Poynting vector)of the electromagnetic fi eld near a sub-wavelength sized slit in a thin metal plate, and demonstrate that the enhanced transmission is accompanied by the annihilation of phase singularities in the power fl ow near the slit.