Nonlinear Attenuation of Laser Radiation by Colloidal Products of Aluminum Target Ablation in Dimethyl Sulfoxide

The mechanisms of nonlinear attenuation of nanosecond laser radiation by metal nanoparticles have been investigated. A nanoscale colloidal system was obtained as a result of the ablation of an aluminum target in dimethyl sulfoxide and investigated by the methods of UV and visible light spectroscopy, dynamic light scattering, and transmission electron microscopy. The average diameter of aluminum nanoparticles is found to be 47 nm. The system is partially aggregated and contains impurities of carbon origin, which are due to the dimethyl sulfoxide decomposition. A possibility of reducing the transmittance at a wavelength of 532 nm by a factor of 5 with an increase in the pulse energy density from 22 mJ/cm2 to 2.9 J/cm2 was shown using the z-scan method. The optoacoustic signals are measured, and a sublinear dependence of their amplitude on the pulse energy is found. Peak pressures are estimated to be 1.6 MPa at the energy density of 3.26 J/cm2 for the colloidal products of aluminum ablation. Based on the sublinear dependence of the acoustic signal amplitude on the pulse energy and pressure, it is concluded that the evaporation processes dominate in the observed effects. An approximate model is proposed, and the peak temperatures of aluminum nanoparticles are estimated to be 3670–4090 K.