Summary form only given. We report the demonstration of high output power (>1 W), single frequency and ultra-short pulse operation (<5 ps) of a newly developed Diode-Pumped broadband Multiple-Quantum-Well Vertical-External-Cavity Surface-Emitting semiconductor Laser (DP-VECSEL). The laser operates cw at room temperature with a low divergence circular TEM/sub 00/ beam and is broadly tunable (>50 nm) by simply changing the lasing spot position on the wafer. We also demonstrate, for the first time to our knowledge, high sensitivity Intra-Cavity Laser Absorption Spectroscopy (ICLAS) with a DP-VECSEL. A detection limit lower than 10/sup -10/ per cm of absorption path has been achieved given ~10/sup -11/ cmHz/sup 1/2/. For this application, the spectro-temporal dynamics of the DP-VECSEL has been studied in the time range from a few microseconds to about one second.