title: Holey-metal lenses: sieving single modes with proper phases.
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.
authors.affiliation: Birck Nanotechnology Center, School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ishii
authors.forename: Vladimir M
authors.initials: VM
authors.lastname: Shalaev
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Kildishev