Material dependence of laser-induced breakdown of colloidal particles in water

Abstract

Laser-induced breakdown of colloidal suspensions, such as polystyrene, ZrO2, and SiO2 particles in diameters of 100-400 nm in water is investigated by nanosecond flash-pumped Nd:YAG laser pulses operating at a wavelength lambda = 532 nm. The breakdown threshold intensity is examined in terms of breakdown probability as a function of laser pulse energy. The threshold intensity for SiO2 particles (1.27x1.0(11) W/cm(2)) with a size of 100 nm is higher than those for polystyrene and ZrO2 particles with the same size, namely 5.7x10(10) and 5.5x10(10) W/cm(2), respectively. Results indicate that the absorption of five photons is required to induce ionization of SiO2 particles, whereas the other particles necessitate four-photon absorption. These breakdown thresholds are compared with those measured by nanosecond pulses from a diode-pumped Nd:YAG laser having a different focusing geometry.