We report on the high-power operation of an optically pumped VECSEL emitting at 1060 rim. The VECSEL structure, grown by MOVPE, consists of resonant periodic gains and 35 pairs of AlAs/AlGaAs DBR. A single In0.28GaAs quantum well is positioned at each antinode of the optical standing wave. The VECSEL chip is water-bonded by capillarity to a diamond heatspreader. 10 W continuous wave operation is achieved with an optical-to-optical conversion efficiency of 44% at room temperature. High efficiency and good thermal stability are mainly due to the optimization of epitaxial quality and the high conductivity of the diamond heatspreader. We have found that the increase of the round trip caused by the heat spreader is about 1%. (c) 2005 Published by Elsevier B.V.