Abstract: A semiconductor laser source using a strained active layer of InGaAsN, introduced by the addition of N in the alloy, to obtain semiconductor laser sources that emit TM-polarized light in the wavelength range above 850 nm. The presence of N in the alloy reduces the lattice constant and produces the desired strain effect, i.e., biaxial tension which raises the light hole band (yielding TM polarization) and produces a narrowing of the band gap. Adding In can reduce the strain in the alloy while maintaining the desired band gap and light-hole/heavy-hole ordering.