Broadband hyperbolic metamaterial covering the whole visible-light region

Nanowire-based hyperbolic metamaterials (HMMs) with rich optical dispersion engineering capabilities are promising for use in miniaturization devices, such as nanophotonic chips and circuits. Herein, based on a one-step and template-free sputtering method, we are capable of precisely tuning the microstructural parameters of Ag nanowires (with a diameter <10 nm) in silica matrix, offering plenty of opportunities to perform hyperbolic dispersion engineering. Thus, the effective plasma frequency of the designed HMMs was shifted into the near-ultraviolet region (∼350 nm), leading to a broadband hyperbolic dispersion feature covering the whole visible-light region. This demonstration could pave the way for the development of metamaterial-based flat lenses, deep-subwavelength waveguiding, and broadband perfect absorbers and sensing, etc.