USE OF GLASSES CONTAINING RARE EARTH OXIDE, ALUMINA, AND ZIRCONIA AND DOPANT IN OPTICAL WAVEGUIDES

The invention provides optical waveguides comprising a glass doped with a rare earth dopant on a surface of the substrate, wherein the glass comprises (a) Al2O3, at least one of REO or Y2O3, and at least one of ZrO2 or HfO2, wherein at least 80 percent by weight of the glass collectively comprises the Al2O3, at least one of REO or Y2O3, and at least one of ZrO2 or HfO2, based on the total weight of the glass; (b) Al2O3, at least one of REO or Y2O3 and at least one of ZrO2 or HfO2, wherein at least 70 percent by weight of the glass collectively comprises the Al2O3, at least one of REO or Y2O3, and at least one of ZrO2 or HfO2, and wherein the glass contains not more than 20 percent by weight SiO2 and not more than 20 percent by weight B2O3, based on the total weight of the glass; or (c) at least 40 percent by weight Al2O3, based on the total weight of the glass, and a first metal oxide other than Al2O3, wherein the Al2O3 and the first metal oxide, collectively comprise at least 80 percent by weight of the glass.