The breakdown processes of silver nanoparticles in the volume of photothermorefractive glasses when they are irradiated with a femtosecond laser (800 nm, 120 fs) is investigated as a function of the dose and energy density of the radiation (0.012–4 J/cm2). It is shown that the amplitude of the plasmon-resonance absorption band of silver nanoparticles decreases as a function of the energy density and irradiation dose until it completely disappears. It is concluded that, under the action of femtosecond pulsed laser radiation, silver nanoparticles undergo photodecomposition as a result of multiphoton interaction, with the formation of finer particles and atoms and their partial photoionization and transition to the ionic state. When irradiation is produced by laser radiation having an energy density greater than 0.5 J/cm2, additional photoinduced absorption arises in the 300–550-nm region, associated with the concentration increase of silver molecular clusters and radiation defects as a result of photoionization of the glass matrix.
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