A model description of the laser-induced free carriers influence upon the point defect generation and optical damage in the wide-gap semiconductors and die1ectrie i presented. The model is based on the following assertions:-the defect creation probability in solid considerably increases compared with its usual ternperathre fluctuation value if the free carriers are involved in defect generation process (so-called recombintion-stimu1ated defect reactions); -the point defect creation in crystal resulting in energy specirum transformation leads to free carriers generation in solid even without the lattice heating. The positive feedback between free carrier and point defect concentrations stimulates the fast increase both cainer and defect densities and under certain conditions results in optical damage of crystal.The conducted analysis makes it possible to assert that:-the optical damage of transparent solids is often due to the e1ectronstimulated defect reactions arising under the wide range oflight irradiation parameters; -the mentioned above process of the defect generation nrnst be taken into account in the analysis of 'aceumu1ative effects" in low absorbing media under multiple laser action with sub-threshold intensities.
The results of theoretical investigation of processes resulting from disturbance of charge equilibrium in a solid nanoparticle, induced by fast ionization under high-intensity ultra-short laser pulse action are presented. Analytical and numerical methods were used to study time evolution of space and energy distributions of moving ions during their spreading away from the particle for various sizes and shapes of the particle as well as various degrees of ionization of its material. The final aim of the presented study is to analyze the influence of the disturbance of charge equilibrium induced by high-intensity ultra-short laser pulses in a solid on parameters of laser-induced damage of the material, and the regularities of the atoms and ions motion of the media in damage area under the action of local laser-induced Coulomb potential.
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
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