The invention is a single-crystal passively mode-locked semiconductor vertical-external-cavity surface-emitting laser (VECSEL). The device can be a single emitter or an array of emitters. The VECSEL structure is grown on a GaAs, InP or GaSb substrate. The device consists of an active region with a number of quantum wells (QW) made of GaInAs, GaInAsP, GaInNAs, GaInNAsSb, AlGaAs or GaAsP. The fundamental lasing wavelength is chosen by the gain material. The gain region is sandwiched between the bottom reflector with reflectivity close to 100% and a partial reflector. A semiconductor spacer layer made of e.g. GaAs or AlGaAs is separating the gain region and a semiconductor saturable absorber. The saturable absorber consists of one or more quantum wells made of GaInAs, GaInAsP, GaInNAs, GaInNAsSb, AlGaAs or GaAsP and a second partial reflector. The quantum wells can be of undoped, n-doped, p-doped or co-doped of such semiconductor material that the optical energy emitted by the gain medium is absorbed by the saturable absorber QW material. The n- and p-contacts are metalized on opposite sides of the semiconductor structure. The laser diode current is flowing through the layer structure partially saturating the semiconductor saturable absorber.