Optical gain calculation for strained quantum well lasers by the fourier expansion method

In this paper, we extend the Fourier expansion method to calculate the optical gain of strained quantum well (QW) lasers within the 6 × 6 Luttinger-Kohn Hamiltonian. The optical matrix elements, in a Fourier expansion framework, can be derived in a simple form by averaging around the axis normal to the well plane. As a numerical example, we calculate the band structure and the optical gain of In_xGa_1-xAs/InGaAsP/InP QW lasers. We also study the effect of the spin-orbit split-off band coupling on the optical gain. It is shown that the calculated results are in reasonable agreement with those obtained by the conventional finite difference method.