RARE-EARTH ION DOPED THIN FILM TECHNOLOGIES

The present disclosure includes a thin film assembly comprising a substrate and an epitaxial crystalline thin film disposed on the substrate, wherein the epitaxial crystalline thin film is a single crystal, wherein at least a portion of the epitaxial crystalline thin film is doped with rare-earth ions at a concentration of less than 100 parts per billion. The disclosure further includes a method of manufacturing a thin film assembly, the method comprising creating, on a substrate and with use of molecular beam epitaxy, an epitaxial crystalline thin film doped with the rare-earth ions at a concentration of less than 100 parts per billion.