Transmittance of a subwavelength aperture flanked by a finite groove array placed near the focus of a conventional lens

Abstract

In this paper, we study the optical response of 1D light harvesting structures that are illuminated by a conventional lens. Our theoretical study shows that high transmission efficiencies are obtained when the structure is placed near the focal plane of the lens. The considered structure is a finite slit-groove array (SGA) with a given number of grooves, which are symmetrically distributed with respect to a central slit. The SGA is nanopatterned on an opaque metallic film. It is found that a total transmittance of 80% is achieved even for a single slit when (1) Fabry-Perot-like modes are excited inside the slit and (2) the effective cross section of the aperture becomes of the order of the FWHMof the incident beam. A further enhancement of 8% is produced by the groove array. The optimal geometry for the groove array consists of a moderate number of grooves (≥4) at either side of the slit, separated by a distance of half the incident wavelength λ. Grooves should be deeper (with depth ≥λ/4) than those typically reported for plane wave illumination in order to increase their individual scattering cross section. © 2014 Optical Society of America.