| The coupling of light with surface plasmons (SP)---collective oscillations of conduction electrons---in metallic nanogratings has attracted significant attention with many exciting observations, including enhanced optical transmission, light collimation, and negative refraction. Our soft nanolithographic approaches, which include replica molding, phase-shifting photolithography, and solvent-assisted nanoscale embossing, are capable of patterning high quality multiscale plasmonic crystals---periodic sub-100 nm metallic arrays---over large-areas. Our fabrication techniques yield plasmonic structures with unique optical properties: ultra narrow SP resonances, polarization-dependent transmission colors, and subwavelength-scale light focus. Furthermore, our approaches also provide opportunities to realize promising plasmonic applications such as plasmonic solar cells and high throughput refractive index sensing. These applications have been limited by small-area plasmonic crystals fabricated by traditional methods such as focused ion beam milling and electron beam lithography. This dissertation describes soft lithographic approaches to generate wafer-scale plasmonic crystals. These structures impact plasmonics substantially because of their unique optical properties: (i) microscale arrays of nanohole arrays that exhibit transmission modes from high-order Bragg modes of surface plasmon polaritons (SPPs); (ii) multiple one-dimensional SPP modes from geometrically controlled two dimensional nanoslit arrays that improve refractive index sensitivities; (iii) plasmonic metamaterials that show tunable SPP modes by changing the shapes and spacings of subwavelength nanoholes; (iv) hybridized localized surface plasmon (LSP) modes from ring-like plasmonic nanoparticles. Such unique plasmonic crystals not only give opportunities to understand fundamental properties of LSPs and SPPs but also provide a platform for promising plasmonic applications. |
