Plasmonics in the near-infrared: Spatial, spectral, and temporal studies of surface plasmon polaritons.

摘要

The field of nanophotonics is finding myriad applications in telecommunications and information technology, microscopy, lighting, and sensing. There is general interest in highly confined and nanoscale optical modes for a number of these applications, with a particular interest in structures that confine electromagnetic fields and energy in volumes smaller than the free space wavelength. Plasmonics, the utilization of coupled photon-plasmon waves in systems with free electrons, in micro- and nanoscale geometric structures has attracted significant recent attention for these purposes.; In this dissertation we explore surface plasmon-polariton (SPP) fields, on nanostructured metal-dielectric boundaries, at frequencies in the near-infrared portion of the electromagnetic spectrum. To couple to these SPP modes from free-space propagating light, arrays of nanoholes etched in metal films are employed. We then utilize a variety of experimental techniques that investigate the physics of SPPs in space, time, and frequency. Various physical phenomena, including enhanced transmission effects and resonantly excited and propagating surface electromagnetic modes, are observed, studied, and explained.; We begin by discussing the basics of SPP excitation and modal propagation properties and present an analytical investigation of gain assisted propagation. We next investigate the spatial and spectral frequency dependent transmission through nanohole arrays. We present novel experimental and analytic results of polarization dependent Fano-type lineshape profiles present in enhanced transmission due to SPP excitation. We further present a method for excitation and direct imaging of SPPs from nanohole arrays and demonstrate coupling to a variety of modes with different in-plane propagating wavevector components. This method is extended to incorporate ultrashort laser pulse excitation and enables space-time imaging of ultrashort SPP fields, both in spatial amplitude and phase, with femtosecond time scale resolution. We ultimately describes the application of this work to the making of a highly parallelized sensor to measure chemical reactions at a surface by generating spatially resolved, reaction dependent, spatial and spectral frequency information.