Abstract

Plasmonic lenses are based on complex combinations of nanoscale high aspect ratio slits. We show that their design can be greatly simplified, keeping similar performance while releasing technological constraints. The simplified system, called Huygens lens, consists in a central aperture surrounded by several identical single mode slits in a thin gold layer that does not rely anymore on surface plasmons. The focusing behaviour with respect to the position and number of slits is investigated, and we demonstrate the interest of this design to get compact array of lenses.

Highlights

  • The development of integrated compact optical sensors requires the miniaturization of lenses at a mesoscopic scale[1]

  • We show that the combination of a central aperture engraved in a thin metallic layer, and surrounded by several identical single mode slits leads to similar light focusing as in plasmonic lenses (PL) while dramatically releasing the technological constraints

  • 52% of the energy incident on the lens aperture is transmitted in the transverse magnetic (TM) polarisation state, which corresponds to the geometrical aperture of the Huygens lens (HL)

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Summary

INTRODUCTION

The development of integrated compact optical sensors requires the miniaturization of lenses at a mesoscopic scale[1]. Fresnel zone plates are used either to focus in-plane surface plasmons [13, 14] or visible light [15]–[17] They have always been demonstrated with a high number of zones, which could be a drawback against the miniaturization of systems and their integration in detector arrays. We show that a 3-slits structure allows to reach numerical aperture in the range of 1 to 3 while keeping a nearly constant efficiency, which is a step toward more compact devices. We call this system a Huygens lens (HL). Relative to the central aperture on the focusing HL properties are investigated

HUYGENS LENS DESCRIPTION
INFLUENCE OF D1 ON LIGHT FOCUSING
INFLUENCE OF THE NUMBER OF EXTERNAL SLITS
PERIODIC ARRAY OF HUYGENS LENSES
Findings
CONCLUSION

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