Plasmonic Crystals: A Platform to Catalog Resonances from Ultraviolet to Near‐Infrared Wavelengths in a Plasmonic Library

Surface plasmons are responsible for a variety of phenomena, including nanoscale optical focusing, negative refraction, and surface‐enhanced Raman scattering. Their characteristic evanescent electromagnetic fields offer opportunities for sub‐diffraction imaging, optical cloaking, and label‐free molecular sensing. The selection of materials for such applications, however, has been traditionally limited to the noble metals Au and Ag because there has been no side‐by‐side comparison of other materials. This feature article describes recent progress on manipulating surface plasmons from ultraviolet to near‐infrared wavelengths using plasmonic crystals made from 2D nanopyramidal arrays. A library of plasmon resonances is constructed in the form of dispersion diagrams for a series of unconventional and new composite plasmonic materials. These resonances are tuned by controlling both intrinsic factors (unit cell shape, materials type) and extrinsic factors (excitation conditions, dielectric environment). Finally, plasmonic crystals with reduced lattice symmetries are fabricated as another means to tailor resonances for broadband coupling.