We report on molecular beam epitaxial growth and characterization of InAs/GaInSb/InAs/AlGaAsSb type-IT miniband-to-bound state W-lasers. Laser core structures were characterized using photoluminescence, high resolution X-ray diffraction and Raman spectroscopy to reveal the best growth conditions. The growth temperature for the laser core was varied in the range between 380° C and 460° C and found to be optimal at 420° C. Optimized laser active regions were embedded between 600 nm AlGaAsSb separate confinement layers which in turn were sandwiched between 1.5 μ m thick n- and p-doped Al0.85Ga0.15As0.07Sb0.93 cladding layers. The upper cladding was capped with a 100 nm p(+)-GaSb contact layer. The growth temperature of the upper separate confinement and cladding layer was varied between 470 ° C and 530 ° C to reveal the influence on laser performance. Laser emission is observed near 3.2 μ m. Devices with uncoated facets, mounted substrate side down could be operated up to a temperature of 185 K in continuous-wave (cw) mode. Single ended output powers of 144 mW in cw mode and 330 mW in pulsed operation were obtained for a 5-period diode laser structure with HR/AR coated mirror facets at an operation temperature of I 10 K. © 2005 Elsevier B.V. All rights reserved.