Analysis of transmittance enhancement for a slab lens formed by sub-wavelength holes array on the metallic film

By investigating the transmittance and phase characteristics of the square holes on the metallic film, we find that the transmittance fluctuates with center distance between holes and appears resonant peaks, which attributes to the surface wave enhanced transmission phenomenon while the corresponding phase retardation through holes keeps constant. Based on this phenomenon, the slab lens can be optimized to a high transmittance by modulating the center distance of the holes. Design results show that the light intensity values at the focal spot of the slab lens can be enhanced from 3 to 14.5 in intensity scale when the center distance changes from 1.25λ to 0.95λ.

► Transmittance and phase characteristics of the square holes are investigated.
► Transmittance fluctuates with center distance between holes.
► Corresponding phase retardation through holes keeps constant.
► Appearing resonant peaks attribute to the surface wave enhanced transmission phenomenon.
► Slab lens can be optimized by modulating the center distance of the holes.