Planoconcave lens by negative refraction of stacked subwavelength hole arrays Beruete, M. ; Navarro-Cía, M. ; Sorolla, M. ; Campillo, I. Abstract Publication: Optics Express Pub Date: June 2008 DOI: 10.1364/OE.16.009677 Bibcode: 2008OExpr..16.9677B