Extended metal nanostructures, such as nanowires or nanoplates, exhibit electron motions at their surfaces that are termed Surface Plasmon Polaritons (SPPs). These modes have momentum, and in single nanostructure studies they can be excited by focusing a laser source at the end or edge of the nanostructure. The properties that define the SPP modes are their wavevector and their propagation length. For nanostructures on a surface (the typical configuration in a microscopy experiment) there are two types of SPP modes: bound modes at the metal-substrate interface and leaky modes at the metal-air interface. In this talk far-field optical experiments will be described (transient absorption microscopy and back focal plane imaging) that measure the wavevectors and propagation lengths of the bound and leaky modes for single nanostructures. In particular the back focal plane imaging experiments allow the measurement of dispersion curves (frequency versus wavevector) for the leaky mode. When the nanostructures are coated will a thin film of dye molecules or quantum dots these curves show an avoided crossing when the SPP of the metal nanostructure and exciton transition of the dye molecules/quantum dots are in resonance. Analysis of the dispersion curve yields the Rabi frequency for the coupling. The back focal plane images also show that the hybrid exciton-plasmon states created suffer increased attenuation compared to the uncoupled SPPs.

Spectroscopy and dynamics of surface plasmon polaritons in noble metal nanostructures

256th National Meeting (2018)

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