Three-dimensional silver nanostructure fabrication through multiphoton photoreduction

Abstract

Metal nanofabrication techniques have become increasingly important for photonic applications with rapid developments in plasmonics, nanophotonics and metamaterials. While two-dimensional (2D) techniques to create high resolution metal patterns are readily available, it is more difficult to fabricate 3D metal structures that are required for new applications in these fields. We present a femtosecond laser technique for 3D direct-writing silver nanostructures embedded inside a polymer. We induce the photoreduction of silver ions through non-linear absorption in a sample doped with a silver salt. Utilizing nonlinear optical interactions between the chemical precursors and femtosecond pulses, we limit silver-ion photoreduction processes to a focused volume smaller than that of the diffraction-limit. The focal volume is scanned rapidly in 3D by means of a computer-controlled translation stage to produce complex patterns. Our technique creates dielectric-supported silver structures, enabling the nanofabrication of silver patterns with disconnected features in 3D. We obtain 300 nm resolution.