Ultrafast thermal modulation dynamics during ripple formation induced by a femtosecond laser multi-pulse vortex beam

Abstract

This work theoretically investigated the ultrafast thermal modulation dynamics during early formation of ripples on Au film induced by femtosecond laser vortex beam irradiation. An extended two-temperature dynamics model that comprehensively considers the optical interference modulation for the formation of seed ripples, transient reflectivity, and non-nonequilibrium thermal transfer was self-consistently built to predict high-contrast ripples formation. The 2D evolutions of the electron and phonon temperature modulations during ripples formation in high non-nonequilibrium state of Au film were obtained via femtosecond laser vortex beam irradiation. It was revealed that the ripples contrast in can be significantly amplified by shortening the laser wavelength, increasing the pulse number, or enlarging the laser fluence of vortex beam. Moreover, the electron-phonon coupling time during ripples formation was fully explored in detail. The studies provide valuable insights into optimizing laser parameters for controlled high-contrast ripple formation on Au films.