A spiral plasmonic lens with directional excitation of surface plasmons.

Qingrui Guo,Chi Zhang,Xinhua Hu

doi:10.1038/srep32345

Abstract

Conventional plasmonic lenses are composed of curved slits carved through metallic films. Here, we propose a new plasmonic lens based on a metallic slit with an auxiliary groove. When the lens is illumined normally, only inward surface plasmon polaritons (SPPs) can be generated and then focused into a hot spot at the center of the lens. The focusing effect is theoretically investigated by varying the groove parameters and incident polarizations. It is found that this phenomenon exists for both the circular and linear polarizations of incidence. Under optimal groove parameters, the intensity of the focal spot in our lens can be 2.5 times of that in one without grooves for both linearly and circularly polarized illuminations.

Highlights

Conventional plasmonic lenses are composed of curved slits carved through metallic films
We show that, via using a metallic slit with an auxiliary groove in plasmonic lenses, outward surface plasmon polaritons (SPPs) can be eliminated for all the circular and linear polarizations of incidence
When the slit is illuminated by a 2D Gaussian light beam with x-polarization from the bottom, SPPs can be excited on the upper surface of the Au film

Summary

Introduction

Conventional plasmonic lenses are composed of curved slits carved through metallic films. SPPs can be generated at a metallic film that has a slit and is illuminated by a light beam from vacuum[17,18,19]. When a lens array is introduced, outward SPPs can interfere in the areas outside lenses.

Results

Conclusion