An output power up to 5 W at 1.48- m wavelength is achieved from an optically pumped semiconductor disk laser. An active region composed of an AlGaInAs/InP heterostructure grown on an InP substrate was wafer fused with an AlGaAs/GaAs Bragg reflector grown on a GaAs substrate. An intracavity diamond heatspreader bonded to the gain structure surface provides efficient heat removal from the active element. The results further validate that the wafer fusion technique offers a flexible platform for high-power disk lasers in a wide wavelength range.