The influence of strain in Ga0.7In0.3AsySb1 - y quantum wells (QWs) embedded in Al0.24Ga0.76AsySb1 - y barriers on the photoluminescence (PL) emission wavelength and intensity has been investigated. The strain was adjusted by varying the As content in the QW and barrier layers. For As mole fractions in the (GaIn)(AsSb) QW layers between y = 0.25 and 0.05, the average strain perpendicular to the growth plane changes from (Delta a/a)(perpendicular to) = 2.0 x 10(-3) to 10.4 x 10(-3) for lattice matched (AlGa)(AsSb) barriers. At room temperature, highest PL intensities are obtained for QW structures with a net compressive strain of(Delta a/a)(perpendicular to) = 8.7 x 10(-3). In order to compensate the compressive strain in the QWs, strain-balanced laser core structures with barriers under tensile strain have been investigated. This was found to allow a reduction of the average strain in the laser core without shifting its emission wavelength. Ridge waveguide large optical cavity (LOC) laser diodes containing three compressively strained (GaIn)(AsSb) QWs embedded between lattice matched (AlGa)(AsSb) barriers show room temperature cw laser emission at a wavelength of 2.26 mu m. For 64 mu m wide and 600 mu m long devices, a differential quantum efficiency of 43 % and a threshold current density of 395 A/cm(2) with a characteristic temperature of T-0 - 110 K are obtained.