Silica‐titania sol‐gel planar waveguides were deposited on silicaglass disks by spin coating.Fluorescence lifetimes as high as 375 μs were measured in neodymium‐doped sol‐gel planar waveguides and 1.78 ms for an erbium‐doped film. Quenching was found to occur for the former at concentrations above 1 at. % of neodymium.