Beta double prime alumina is provided having a sensible amount of at least one polyvalent cationic species intercalated therein. In accordance with a preferred embodiment, such beta double prime alumina is provided having trivalent and/or tetravalent cationic species intercalated therein, especially species derived from the lanthanide and actinide series of elements. Certain of the foregoing materials exhibit phosphorescence or fluorescence, and some are believed to be capable of producing laser emission upon suitable irradiation. Methods for modifying beta double prime aluminas comprising contacting crystals of the aluminas with polyvalent cation-containing salts such as in the molten state or in the gaseous state are also provided. Laser and other optical devies are disclosed employing the modified beta double prime aluminas of this invention.