Raising its share to 52 percent, Schott Corp. of Yonkers, N.Y., has acquired majority ownership of university spin-off U.L.M. Photonics GmbH of Ulm, Germany, which has built and developed research, design and manufacturing facilities for vertical-cavity surface-emitting lasers (VCSELs). Schott also plans to sell, spin-in or close Schott Optovance Inc. of Southbridge, Mass., by the end of the year. The supply of products to its customers will be assured during the restructuring.