Nonlinear attenuation of laser radiation by colloidal products of aluminum target ablation in dimethyl sulfoxide

Abstract: We study nonlinear attenuation of nanosecond laser irradiation by metal nanoparticles. Nanosized colloids are prepared by laser ablation of an aluminium target in dimethyl sulfoxide (DMSO) and ablation products are characterised with UV-vis spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM). The average diameter of aluminium nanoparticles is found to be 47 nm. The system is partly aggregated and contains carbon-based impurities associated with DMSO decomposition. The z-scan technique shows that transmittance at a wavelength of 532 nm can be reduced by a factor of five with an increase in the pulse energy density from 22 mJ·cm^–2 to 2.9 J·cm^–2. Optoacoustic signals are measured and a sublinear dependence of their amplitude on the pulse energy is found. Peak pressures for colloidal aluminium ablation products are estimated to be 1.6 MPa at an energy density of 3.26 J·cm^–2. Based on the sublinear nature of the dependence of the acoustic signal amplitude on the pulse energy and pressure, we make a conclusion that evaporation processes play a predominant role in the observed effects. An approximate model is proposed and the peak temperatures of aluminium nanoparticles are estimated at 3670–4090 K.

Keywords: ablation synthesis, metal nanoparticles, #z-scan, optoacoustic effect, evaporation, nonlinear attenuation of radiation.