Femtosecond laser-induced nanogratings formation assisted by silver ions in a gallophosphate glass and correlated optical properties

Abstract

We report on the significant role of silver ions during femtosecond laser-induced formation of nanogratings (NGs) at the surface of high optical quality gallophosphate glasses that we develop. Compared to the non-doped glass matrix, the silver-containing glass showed remarkable silver-dependent behaviors, namely lower fluence thresholds of NGs formation and higher NGs quality with much smoother shapes. Additionally, the silver-containing glass also led to a multi-functional behavior since fluorescence and effective second-order nonlinear optical properties were correlatively observed, resulting from the laser-induced formation of silver clusters and of a space-charge separation, respectively. These silver-related linear and nonlinear optical properties were shown to occur prior the NGs formation. By decoupling the origin of the free ionized electrons from the glass matrix network, we demonstrate that noble metal ions can play the role of a reservoir of available electrons that can facilitate the incubation processes and NGs formation, improving thus the NGs quality. Such a material doping can be thought as a material engineer approach by means of extrinsic doping.