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) Al.sub.2O.sub.3, at least one of REO or Y.sub.2O.sub.3, and at least one of ZrO.sub.2 or HfO.sub.2, wherein at least 80 percent by weight of the glass collectively comprises the Al.sub.2O.sub.3, at least one of REO or Y.sub.2O.sub.3, and at least one of ZrO.sub.2 or HfO.sub.2, based on the total weight of the glass; (b) Al.sub.2O.sub.3, at least one of REO or Y.sub.2O.sub.3, and at least one of ZrO.sub.2 or HfO.sub.2, wherein at least 70 percent by weight of the glass collectively comprises the Al.sub.2O.sub.3, at least one of REO or Y.sub.2O.sub.3, and at least one of ZrO.sub.2 or HfO.sub.2, and wherein the glass contains not more than 20 percent by weight SiO.sub.2 and not more than 20 percent by weight B.sub.2O.sub.3, based on the total weight of the glass; or (c) at least 40 percent by weight Al.sub.2O.sub.3, based on the total weight of the glass, and a first metal oxide other than Al.sub.2O.sub.3, wherein the Al.sub.2O.sub.3 and the first metal oxide, collectively comprise at least 80 percent by weight of the glass.