Investigation of enhanced and suppressed optical transmission through a cupped surface metallic grating structure.

Two-dimensional finite-difference time-domain (FDTD) method has been performed to numerically investigate the transmission through a one-dimension cupped surface metallic grating structure. The concept of coupling of optical modes in the notches and main slits, introduced by Crouse and Keshavareddy [1], is examined further in our work. Unexpected phenomenon is shown that even horizontal surface plasmons (HSPs) are inhibited, the transmission still can be enhanced or suppressed. And the periodicity of transmission depending on the phase change of the light striking on the grating surface is discovered. A hybrid optical mode combined by cavity mode and diffracted evanescent wave mode [2] is introduced to analyze the phenomenon.