  Plasmonic metal nanostructures are an integral part of nanophotonic device
applications owing to their ability to generate strong localized
electromagnetic fields when illuminated from the far-field. These
nanostructures can be prepared in the laboratory with precise shape and size by
various chemical and physical synthesis techniques as demonstrated in recent
years. Typically, the size of these structures is in the range of few nm to a
few hundred nm, i.e., much below the wavelength of light of observation or
excitation. The focus of this chapter is to exploit the ultrafast response of
metal nanostructures following femtosecond laser pulse excitation. Femtosecond
laser pulses are very important experimental probes to explore the material
response at an ultrafast time scale (~10-10,000 fs) on the order of the
electronic and vibrational wave packet dynamics in solids and molecules.
Broadly, after ultrafast optical excitation the system of study undergoes
various microscopic dynamical changes which can be monitored in real time so as
to understand the intermediate stages before the system returns to the
equilibrium.
