Nanoporous Metallic Network as a Large-Scale 3D Source of Second Harmonic Light

We introduce a large-scale nanoporous metallic network whose building blocks are assembled into an effective nonlinear conductive material, with a considerable conversion efficiency in a wide range of optical wavelengths. The high nonlinear response results from the complexity of the three-dimensional (3D) network structure having a large surface area as well as hot spots in deeper focal plans of the metallic network. Broadband responses of the metallic network are observed by both second harmonic generation (SHG) and cathodoluminescence (CL). The large-scale dimension and generation of randomized hot spots make this 3D metallic network a promising platform for applications like photocatalysis, sensing, or optical imaging such as structured illumination microscopy.