2 research outputs found
Pump-Selective Spectral Shaping of the Ultrafast Response in Plasmonic Nanostars
Plasmonic nanostructures are, to date, well-known to
offer unique
possibilities for the tailoring of light–matter interactions
at the nanoscale. Most recently, a new route to ultrafast all-optical
modulation has been disclosed by combining the resonant features of
plasmonic nanostructures with the giant third-order optical nonlinearity
of noble metals regulated by highly energetic (hot) carriers. In this
framework, a variety of nanostructures have been designed, with special
attention to shapes featuring tips, where extreme and highly sensitive
field enhancements (hot spots) can be attained. Here, we report on
a broadband pump–probe spectroscopy analysis of an ensemble
of spiky star-shaped nanoparticles, exploring both the perturbative
and nonperturbative regimes of photoexcitation. The experiments are
corroborated by semiclassical numerical simulations of the ultrafast
optical response of the sample. We found that the peculiar hot spots
supported by the star tips allow one to easily control the spectral
shape of the transient optical signal, upon tuning of the pump wavelength.
Our results elucidate the ultrafast response of hot electrons in star-shaped
nanostructures and contribute to the understanding of the tip-mediated
enhanced nonlinearities. This work paves the way to the development
of ultrafast all-optical plasmonic modulators for pump-selective spectral
shaping