Dynamics of laser-induced damage of spherical nanoparticles by high-intensity ultrashort laser pulses

Abstract

Damage of a metal spherical nanoparticle by femtosecond laser pulses is analyzed by splitting the overall process into two steps. The fast step includes electron photoemission from a nanoparticle. It takes place during direct action of a laser pulse and its rate is evaluated as a function of laser and particle parameters by two approaches. Obtained results suggest the formation of significant positive charge of the nanoparticles due to the photoemission. The next step includes ion emission that removes the excessive positive charge and modifies particle structure. It is delayed with respect to the photo-emission and is analyzed by a simple analytical model and modified molecular dynamics. Obtained energy distribution suggests generation of fast ions capable of penetrating into surrounding material and generating defects next to the nanoparticle. The modeling is extended to the case of a nanoparticle on a solid surface to understand the basic mechanism of surface laser damage initiated by nano-contamination. Simulations predict embedding the emitted ions into substrate within a spot with size significantly exceeding the original particle size. We discuss the relation of those effects to the problem of bulk and surface laser-induced damage of optical materials by single and multiple ultrashort laser pulses. Downloaded From: http://opticalengineering.spiedigitallibrary.org/ on 05/18/2015 Terms of Use: http://spiedl.org/terms Optical Engineering 121816-5 December 2012/Vol. 51(12) Komolov et al.: Dynamics of laser-induced damage of spherical nanoparticles by high-intensity : : : Downloaded From: http://opticalengineering.spiedigitallibrary.org/ on 05/18/2015 Terms of Use: http://spiedl.org/terms

Ionization of nanoparticles by supershort moderate-intensity laser pulses

“…For example, it has been proposed to describe the tunnel mechanism in a wide range of laser intensities 21 by means of the Fowler effect, 19,20 assuming that the laser radiation induces a triangular potential barrier at distances of the order of a quarter wavelength beyond the limits of the nanoparticle. 21 Contributions from surface effects and Debye screening, which modify the shape of the barrier only within several nanometers of the particle's surface, were neglected in this case. Various semiclassical approaches to the description of the tunnel effect [5][6][7][8]22 were developed for the case of highintensity femtosecond pulses.…”

“…Two mechanisms for electron emission are usually considered in the theoretical description of the photoelectric effect-tunnelling through the surface potential barrier, overcome by an external electric field [5][6][7][8][17][18][19][20][21][22] [ Fig. 1(a)], and electron excitation to levels with enough energy to escape from the metal 18,21 [ Fig.…”

A computational analysis of nanoparticle-mediated optical breakdown

“…Giammanco et al [180] include photofragmentation of gold nanoparticles in his model and discussed the roles of melting, evaporation, thermionic emission and photo-assisted ionization during picosecond laser exposures. Komolov et al [181] studied the damage of a metal spherical nanoparticle by femtosecond laser pulses by modelling electron photoemission and the formation of positively charged nanoparticle followed by ion emission with removal of the excessive positive charge, which modifies particle structure.…”

“…The PTE of electrons off the surface of a nanoparticle positively charges the nanoparticle and creates charged double layer near the surface of nanoparticle. This phenomenon may lower the PTE rate and should be studied for in the future [61,181,183].…”