Holey-Metal Lenses: Sieving Single Modes with Proper Phases

Satoshi Ishii, Birck Nanotechnology Center, Purdue University
Vladimir M. Shalaev, Birck Nanotechnology Center, Purdue University
Alexander V. Kildishev, Birck Nanotechnology Center, Purdue University

Abstract

We study a planar, holey-metal lens made as a set of concentric circular arrays (rings) of nanoscale holes milled in a subwavelength-thick metal film. Each nanohole-a finite-length, circular, single-mode waveguide with a radius-dependent mode index-is used as a phase-shifting element. Our experimental results confirm that the focusing properties of our polarization-independent, holey-metal lens milled in a 380-nm-thick gold film and illuminated with 531 nm light fits the analytical model well. The proposed concept could offer an alternative to conventional refraction microlenses and open up a vital path toward on-chip or fiber-end planar photonic devices for biosensing and imaging.

Discipline(s)

Nanoscience and Nanotechnology