Condensed Matter Physics Seminar: Nonlinear scattering from metal nanostructures: from cw to femtosecond times

Abstract:

The last two decades have seen a steady growth of interest in nano-plasmonics, i.e., in the interaction of light with metal nanostructures. This research line obviously requires comprehensive models of the response of the metal components to the incident light which are compatible with experimental observations. While the models for the linear response of the metal component are extremely well understood and in excellent agreement with measurements, our understanding of the nonlinear response (i.e., the response to intense laser illumination) is more limited.

In this talk, I will discuss two generic configurations of laser-illuminated metal nanostructures for which the intensity-dependence of gold permittivity is only partially understood. First, I will discuss the intriguing recent experimental measurements of the scattering from metal nanoparticles under continuous wave (CW) illumination, which were initially associated incorrectly as population saturation and reverse saturation effects. Second, I will discuss the femtosecond spatio-temporal dynamics of hot (i.e., non-thermal) electrons in a laser-illuminated metal film, and provide comprehensive modelling of the gold permittivity in these conditions, including the contribution of non-equilibrium electron distribution, of intraband and interband transitions, thermal effects (Fermi smearing and band shifting) etc.. I will further show how we can exploit this dynamics to realize unusual wave physics interactions such as a spectral exchange between short and long pulses, time-reversal of ultrashort optical pulses and more. Finally, I will discuss various future directions and potential applications.

Seminar Organizer: Prof. Shimshon Barad