Linear and Nonlinear Optical Properties of Well‐Defined and Disordered Plasmonic Systems: A Review

Abstract Disordered metallic nanostructures have features that are not realized in well‐defined nanometallic counterparts, such as broadband light localization and inhomogeneous refraction index at the nanoscale. Disordered metal systems with a networked inner architecture have both particles and voids with subwavelength dimensions which are randomly 3D organized in space. These disordered structures are benefited from high surface area and damage stability, permit guest materials permeability, and can be achieved in large scales employing less costs and expertise. Their abundant nanosize gaps and sharp tips can interact with incident light over a broadband range to generate a rich pattern of hot‐spots and can therefore function as an artificial leaf, for example. Here, the linear and nonlinear optical properties of both well‐defined and disordered plasmonic structures are reviewed with a focus on largescale 3D metallic networks. An efficiency comparison of those structures as an optical source for second harmonic generation is presented as well.