New Aluminosilicate Glasses as High‐Power Laser Materials

In the past few years, aluminosilicate glasses of an extremely broad compositional range have been prepared and analyzed to scan this glass type for its potential use as high‐power laser material. The tested network modifier ions included Li + , Na + , K + , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Zn 2+ , Pb 2+ , Y 3+ , and La 3+ . Preliminary investigations have been conducted with Sm 3+ ‐ and Eu 3+ ‐doped glasses; selected glass compositions have also been prepared with Yb 3+ doping for laser testing. It has been found that low refractive indices/low average molecular weights/low densities of the glasses in most cases support relatively long fluorescence lifetimes of the doped ions. It was further concluded that the phonon energy of the molecular network of the glasses does not affect the fluorescence properties of the doped samples. The mechanical properties such as Young's modulus, Vickers hardness, and fracture toughness generally increase with increasing field strength of the network modifier ion for constant stoichiometric ratios of the glass components. The lowest potential thermal stress values were found for zinc and magnesium aluminosilicate glasses, which also have relatively high field strengths. Taking all these facts into account, a ternary lithium aluminosilicate and a mixed lithium magnesium aluminosilicate glass doped with Yb 3+ have been prepared in high optical quality and tested with respect to their laser performance. The fluorescence lifetime values are somewhat lower than in well‐established Yb 3+ ‐doped laser materials, such as fluoride phosphate glass or single crystalline calcium fluoride. Nevertheless, the aluminosilicate glasses show exceptionally high absorption and emission cross sections, smooth and very broad amplification profiles, as well as much better thermomechanical properties. Quantum efficiencies close to unity could be reached by consequently removing dissolved OH from the glass melt.