We present a physical model that explains several sequential stages of the conversion of optical to acoustical energy when irradiating diluted suspensions of metal nanoparticles with laser pulses. Optical absorption and scattering of a single particle driven by plasmon resonance interactions in an aqueous medium are considered. Thermal effects produced by laser-irradiated nanoparticles, dynamics of vapor bubble formation, and acoustic signals from expanding bubbles formed around heated nanoparticles are calculated. Stochastic features of the pressure magnitude emitted as a result of low-fluence irradiation of suspensions are also discussed. The probabilistic distribution of pressure magnitude from individual bubbles was found to obey Zipf's law for low concentrations of nanoparticles, while increasing their concentration brings the pressure magnitude distribution into conformance with the Gaussian law.

No abstract

A nanoscale chaotic relief structure appears as a result of subthreshold single shot femtosecond laser ablation of gold films in the regimes of fabrication of microbumps and nanospikes, but only for a relatively thick film. The observed nanoablation tendency versus film thickness makes it possible to suppose the existence of a sub surface temperature maximum in thicker gold films and its absence within thinner film, which results from competing evaporative cooling and electronic heat conduction, as demonstrated by numerical simulations of the thermal dynamics.

No abstract