Ultrafast Response of Plasmonic Nanostructures

Abstract

Ultrafast photoresponse of plasmonic nanostrucutres, specifically, nanoparticles has been discussed here. Femtosecond laser pulses are useful not only for the time-resolved investigations but also to look at the optical nonlinearities in materials which are primarily electronic at such time-scales. Like the linear photoresponse such as absorption and scattering cross-sections, ultrafast nonlinear optical response also gets emensely enhanced at wavelenths near the surface plasmon resonace of the nanosystem under study. In a time-resolved measurement, typically the electronic scattering processes are studied, however, the confined accoustic phonons due to the finite size effects of the nanostrucutres can also modify the ultrafast time-resolved response. Although, Raman spectroscopy and infrared absorption spectroscopy are the popular techniques for studying phononic properties of the nanostructures, terahertz time-domain spectroscopy using ultrashort terahertz pulses also has shown potential to become another important characterization technique for nanoparticles specially at very low frequencies where other techniques are difficult to reach. We have attempted to present a comprehensive account of the above topics by including essential background given in the beginning of the chapter and subsequently discussing some of the important experimental results from the recent literature along with our results on metal nanoparticles.