Spectral analysis study on the UV photosensitive properties and mechanisms of photo-thermo-refractive glass

Abstract

The cerium element co-exists in the forms of Ce⁴⁺and Ce³⁺in the photo-thermo-refractive (PTR) glass matrix, with the concentration of the photosensitive factor Ce³⁺ determining the photosensitive properties of PTR glass. This study investigates the effects of various fundamental and doping components on the Ce³⁺ content and photo-sensitivity of PTR glass, offering a detailed discussion on the photosensitive mechanism of PTR glass under continuous and femtosecond UV laser irradiation, as well as the dynamic transformation process of internal particles. The results reveal that an increase in Na₂O content slightly decreases the Ce³⁺ content in PTR glass, while an increase in CeO₂ content simultaneously elevates the Ce³⁺/Ce⁴⁺ content. Sb₂O₃/SnO₂ doping significantly enhances the Ce³⁺ content in PTR glass at the constant CeO₂ content. Under continuous UV laser irradiation at 325 nm, most of the Ce³⁺ ions converted to [Ce³⁺]⁺accompanied by absorbing photon energy and releasing electrons. An increase in irradiation dose facilitates the formation of more Ag⁰ atoms, while variations in irradiation power primarily augment the number of free electrons within the glass matrix. In terms of the photosensitive mechanism during irradiation with a 343 nm femtosecond laser, once the single pulse energy surpasses the nonlinear threshold of the material (>0.3 μJ), PTR glass releases free electrons through two ways: two-photon absorption by Ce³⁺and multiphoton absorption by the glass matrix. Meanwhile, the high temperature field generated by femtosecond laser irradiation can induce the formation of silver nanopraticles (Ag-NPs) in PTR glass directly.