A theoretical revisit of giant transmission of light through a metallic nano-slit surrounded with periodic grooves

The giant transmission of light through a metallic nano-slit surrounded by periodic grooves on the input surface is revisited theoretically. It is shown that the influence to the transmission comes from three parts: the groove-generated surface plasmon wave (SPW), the nano-slit-generated SPW and the incident wave. The groove-generated SPW is the main factor determining the local field distribution around the nano-slit opening, which is directly related to the transmission through the nano-slit. The nano-slit-generated SPW can be considered as a disturbance to the light distribution on the input surface. The influence of the incident wave can be strongly reduced when strong surface plasmon wave is generated on the input surface by many periods of deep grooves. Our study shows that the slit-to-groove distance for a maximal transmission through the nano-slit surrounded with periodic grooves can not be predicted by several previous theories, including the magnetic field phase theory of a recent work (Phys. Rev. Lett. 99, 043902, 2007). A clear physical explanation is given for the dependence of the transmission on the slit-to-groove distance.