The naturally disordered rough silver films that are grown with the Tollens silver mirror reaction provide a fascinating plasmonic platform that unites fundamental phenomena with practical utility. The extraordinary optical enhancement factors that result from their complex resonances enable single molecule surface-enhanced Raman (SERS) studies as well as an amplified, intrinsic nonlinear response. Under pulsed infrared excitation, supercontinuum emission and second-harmonic generation are observed from discrete nonlinear hot spots, which can be used as facile far-field, background-free probes of the plasmon resonances. Structure-property relationships between the plasmons and film morphology can be unraveled by combining single nonlinear hot spot spectroscopy with electron microscopy of films with varying surface coverage. Upon transitioning from spatially localized resonances of nanoparticles to delocalized resonances of larger metal structures, the single nonlinear hot spots exhibit multiple extraordinarily narrow resonances with line widths as small as 7meV, two orders of magnitude narrower than the supercontinuum generated.

Unveiling plasmon delocalization and ultranarrow resonances in rough silver films with single nonlinear hot spots

245th National Meeting (2013)

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