Ultrafast near-field enhancement dynamics in a resonance-mismatched nanorod excited by temporally shaped femtosecond laser double pulses

Abstract

The spatial–temporal dynamics of the near e-field enhancement in a resonance-mismatched nanorod irradiated by the femtosecond laser double pulses is theoretically investigated. A model combining the non-equilibrium electron excitation dynamics and the near field scattering was built for well exploring ultrafast dynamics of the e-field enhancement around the nanorod. It is revealed that the average enhancement factor can be evidently improved with increasing the double pulses separation. The energy ratio of the temporally shaped double pulses with respect to the highest enhancement factor shows an evident decrease with the increasing the total laser fluence. In addition, the most evident promotion of average enhancement factor from 51.2 to 78.8 can be acquired under laser fluence of 0.7Fth, which could be attributed to the temperature modulation of electron states excited by the temporally shaped double pulses. The study provides the base for understanding ultrafast plasmon dynamics for advancing the applications such as fs super-resolution fabrication, fs near field imaging and the generation of ultrashort extreme-ultraviolet pulses.