Rofin-Sinar Laser GmbH of Hamburg, Germany, an affiliate of Rofin-Sinar Technologies Inc. of Plymouth, Mich., has purchased 80 percent of the common stock of m2k-laser GmbH of Freiburg, Germany, in a cash transaction. The remaining 20 percent is held by two of the founders of m2k-laser and by Fraunhofer Gesellschaft of Munich. The acquired company — a manufacturer of tapered diode lasers, tapered amplifiers and semiconductor laser products for scientific and medical applications — will continue to operate independently.