Controlling emission and nonlinearity with plasmonic metamaterials

Metamaterials encompass a broad class of structures whose electromagnetic response is driven by their geometry in addition to their composition. Plasmonic nanowire metamaterials provide a platform for engineering optical response from dielectric to epsilon-near-zero to strongly anisotropic (hyperbolic) regimes. Importantly, these metamaterials support exotic additional electromagnetic waves. From the effective medium standpoint, these waves can be described by nonlocal (spatially dispersive) permittivity. In this talk we present a theory of nonlocal electromagnetism in nanowire metamaterials and analyze the effect of optical nonlocalities on spontaneous emission and nonlinear optics in these composites. We show that additional electromagnetic modes can drastically increase local density of photonic states, causing significant enhancement of decay rates. We also demonstrate that plasmonic composites can be used to engineer bulk second-order nonlinearities, with amplitude of effective nonlinear polarizability comparable to that in LiNb and KDP. Finally, we show that geometry of nanowire composites can be used as an important parameter to control polarization properties of structural second harmonic generation.