Magnesium aluminosilicate glasses as potential laser host material for ultrahigh power laser systems

Abstract

Magnesium aluminosilicate glasses doped with 0.2 mol% Sm₂O₃ (1 × 10²⁰ Sm³⁺ cm⁻³) have been prepared in a very broad compositional range. The effect of the MgO, Al₂O₃ and SiO₂ concentrations as well as the effect of partial substitution of MgO by CaO, SrO, BaO, ZnO or MgF₂ have been studied. Increasing the network modifier concentration results in decreasing the glass transformation temperature and increasing the coefficient of thermal expansion due to the formation of non-bridging oxygen sites and decreasing glass network connectivity. Although the network connectivity is changed substantially by the addition of network modifier oxides, the maximum phonon energy and the fluorescence lifetime of Sm³⁺ are not affected. Equimolar replacement of up to 9 mol% MgO by MgF₂ results in increasing Sm³⁺ fluorescence lifetimes without increasing the coefficient of thermal expansion or decreasing the glass forming ability. Glasses with fairly small thermal expansion coefficients (≥3.2 × 10⁻⁶ K⁻¹), low thermal stress values (≥0.5 MPa K⁻¹), broad fluorescence emission peaks and fluorescence lifetimes in the range from 2.4 to 2.8 ms are obtained. Such glasses are interesting candidates for laser host materials in ultrahigh peak power laser systems.