Comparision of linewidth enhancement factor for compressively strained AlGaInAs and InGaAsP quantum well lasers

We have compared and analyzed the theoretical possibility for the extreme reduction in the linewidth enhancement (alpha-factor) in strained layer quantum-well (QW) lasers for AlGaInAs and InGaAsP material. Valence band structure and optical gain in both types of QWs under compressive strain have been calculated using 4x4 Luttinger-Kohn Hamiltonian. The Luttinger parameters of these quaternary materials were determined from the linear interpolation between the values of their respective binaries. The alpha-factor has been calculated as the ratio of the carrier induced change in real component of the complex refractive index to that in imaginary component of the refractive index. We have used Kramers-Kronig relations to calculate the refractive index change due to carrier induced. The alpha-factor was up to 1.5 times smaller in AlGaInAs QW than in InGaAsP QW lasers. The material modal differential gain is found to be approximately 1.38 times larger and material carrier induced refractive index change is 1.16 times smaller in the former material than the latter, respectively.