The optimization of MBE growth conditions and layer structures for room temperature operation of 2.26 mum AlGaAsSb/GaInAsSb laser structures is investigated. Index guided triple quantum well large optical cavity diode lasers with 64 mum x 1000 mum cavities and high reflection/antireflection coated facets reveal a cw output power of 350 mW at T = 280 K. An internal quantum efficiency eta (i) of 69%, internal losses ri of 7.7cm(-1) and a threshold current density for infinite cavity length of j(infinity) = 144 A/cm(2) are obtained for this structure.