Diode-pumped semiconductor disk lasers are based on the principle of diode-pumped solid-state disk lasers. This relatively new type of laser is also referred to as VECSEL (vertical external cavity surface emitting laser). Semiconductor disk lasers show excellent beam characteristics in combination with high output power. With this novel approach, the current injection problems of VCSELs and the facet degradation effects of edge-emitting lasers due to the high optical intensities at the laser mirrors can be overcome. Furthermore the external cavity of the disk laser can be equipped with additional elements such as nonlinear crystals for frequency doubling, In this paper we present an InAlGaAs-based semiconductor disk laser with intracavity frequency doubling having an output power of 23 m W at 491 nm.