title: Plasmonic superlensing in doped GaAs.
abstract: We demonstrate a semiconductor based broadband near-field superlens in the mid-infrared regime. Here, the Drude response of a highly doped n-GaAs layer induces a resonant enhancement of evanescent waves accompanied by a significantly improved spatial resolution at radiation wavelengths around λ = 20 μm, adjustable by changing the doping concentration. In our experiments, gold stripes below the GaAs superlens are imaged with a λ/6 subwavelength resolution by an apertureless near-field optical microscope utilizing infrared radiation from a free-electron laser. The resonant behavior of the observed superlensing effect is in excellent agreement with simulations based on the Drude-Lorentz model. Our results demonstrate a rather simple superlens implementation for infrared nanospectroscopy.
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research , Bautzner Landstraße 400, 01328 Dresden, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Fehrenbacher
authors.forename: Stephan
authors.initials: S
authors.lastname: Winnerl
authors.forename: Harald
authors.initials: H
authors.lastname: Schneider
authors.forename: Jonathan
authors.initials: J
authors.lastname: Döring
authors.forename: Susanne C
authors.initials: SC
authors.lastname: Kehr
authors.forename: Lukas M
authors.initials: LM
authors.lastname: Eng
authors.forename: Yongheng
authors.initials: Y
authors.lastname: Huo
authors.forename: Oliver G
authors.initials: OG
authors.lastname: Schmidt
authors.forename: Kan
authors.initials: K
authors.lastname: Yao
authors.forename: Yongmin
authors.initials: Y
authors.lastname: Liu
authors.forename: Manfred
authors.initials: M
authors.lastname: Helm
keywords: Superlens; diffraction limit; near-field microscopy; semiconductor; surface plasmons