Modal analysis of separate-confinement heterojunction lasers with inhomogeneous cladding layers.

Separate-confinement heterostructure lasers with thin active regions are analyzed. For four different interiorcladding-region refractive-index spatial variations, i.e., step, triangular, parabolic, and inverted parabolic, waveguidemodes are calculated and thresholds are compared. Based on optical considerations alone, the step-indexprofile has the lowest threshold; however, for optimum cladding thicknesses the differences are not great.