Molecular beam epitaxial growth and operation of quaternary GaInAsSb/AlGaAsSb-based optically pumped vertical-external-cavity surface-emitting lasers (VECSEL) emitting at wavelengths 2.X mu m are reported here. The epitaxial layer sequence of a VECSEL consists of three different sections: a distributed Bragg reflector (DBR), an active region, and a window layer terminated by a capping layer. The Al content of the AlGaAsSb layers Varies between 100% in the DBR and 30% in the barriers separating the compressively Strained GaInAsSb quantum wells (QW) in the active region. While the active region was grown without growth interruption, growth had to be interrupted at the interfaces between the above-mentioned sections to adjust the group-HI cell temperatures for different flux settings. At the growth interruption interfaces secondary-ion mass-spectrometry revealed the unintentional incorporation of In at a concentration equivalent to 1-2 monolayers. Inspire of the formation of InAsSb-like interfacial layers between the DBR and the active region on the one hand, and the active region and the window layer on the other, high-performance VECSELs emitting in the 2.0-2.3 mu m wavelength range have been grown. A maximum output power of 3.4 W at 2.25 mu m and -10 degrees C heat-sink temperature has been achieved with a maximum optical-to-optical power conversion efficiency of 24%. (C) 2008 Elsevier B.V. All rights reserved.