Focus of this work is the optimization of growth to achieve high quality laser material for emission at 1.3 mum and beyond. GaAs/CaAsN/InCaAsN heterostructures were grown by solid source molecular beam epitaxy. To achieve optimum crystal quality of InGaAsN heterostructures, growth was followed by a high temperature treatment at about 700 degreesC, The high optical quality of our annealed material is attested by large exciton recombination lifetimes (more than 2 ns). Consequently, a decrease of single quantum well transparency current density down to 100 A/cm(2) is found and SWQ lasers with threshold current densities as low as 350A/cm(2) have been made. This represents clearly the lowest laser thresholds reported so far for emission around 1.3 mum from the InGaAsN material system.