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Dilute nitride Ga(In)NAs/GaAsSb ldquoWrdquo type II quantum wells on GaAs substrates have been grown by metal-organic chemical vapor deposition (MOCVD). Design studies underscore the importance of nitrogen incorporation to extend the emission wavelength into the 1.5 mum region as well as increase the electron confinement, given the material strain relaxation limitations. These studies also indicate that the Sb content of the GaAs1-xSbx hole well is required to be greater than x ~ 0.2, to provide adequate hole confinement (i.e., DeltaEnu > 150 meV). Photoluminescence (PL) and electroluminescence (EL) studies are used to characterize the optical transitions and compare with a ten-band bm k.p simulation. We find that the lowest energy type II transition observed is in good agreement with theory. Preliminary results are presented on diode lasers with two- and three-stage ldquoWrdquo-active regions that exhibit emission that is blue-shifted from the PL, due to charge separation and carrier band-filling of higher energy transitions. Further structure optimization, including multiple-stage (eight to ten W-stages) active regions is required to lower the threshold carrier density and minimize carrier band-filling and built-in electric field effects resulting from charge separation. Dilute nitride materials, such as GaAs1- y-z Sby Nz /InP, are also under development offering potential for wavelength extension into the mid-IR employing InP substrates.