Abstract

The interest to the detailed formation of silver nanostructures inside our optimized non-commercial phosphate glass [1-5] occurs because of the possibility to create compact optical data storage using the fluorescence signal from laser-induced silver clusters [6]. In this work a model and the associated numerical simulation of silver nanostructure formation under femtosecond laser pulse irradiation [1-4] are presented. The laser heating process together with the heat diffusion influences on the diffusion and kinetic reactions of the silver species (Ag⁺ , Ag⁰). The model accounts for the following reactions: photoelectrons are trapped by Ag⁺ : Ag⁺ + e⁻ → Ag⁰, holes trapped by Ag⁺ : Ag⁺ + hole⁺ → Ag²⁺ , silver cluster formation: $A{g}^{+}+A{g}^0\to A{g}_2^{+}$, its photodissociation $A{g}_2^{+}+\hslash \omega \to A{g}^{+}+A{g}^{+}+e^{-}$ and electron-hole recombination. Since laser-induced species of silver clusters are not fully attributed yet, we propose here to restrict the model to the formation of the $A{g}_2^{+}$, to describe the distribution of the silver clusters. Thus, these kinetic reactions drive the appearance of the stable silver clusters $(A{g}_m^{x+},m>2)$ [1, 2] and the on-axis photodissociation provides the ring-structure formation of stable silver clusters around the high absorption area [1-4]. The model reproduces the process of laser-matter interaction of up-to 10⁴ laser pulses (1030 nm, 470 fs, 50-300 nJ, and focused diameter1.2 μm) with the silver-doped phosphate glass. The numerically obtained parameters of the silver ring-shaped nanostructures are closed to the parameters observed experimentally (Fig.1). The ring radius reaches the values ~ 0.6 - 1 μm depending on the input pulse intensity. The width of the ring structure is in the range 100-300 nm.

© 2015 IEEE