Abstract
A method for calculation of refractive indices in III–V compounds at energies below the direct band edge is presented. Spectral dependence of the refractive-index data is analyzed on the basis of simplified models of the interband transitions. The theoretical prediction shows a quite good agreement with the experimental data of III–V binaries. This model is also applied to InGaAsP quaternaries lattice matched to InP. The refractive-index steps between InGaAsP and InP are obtained for a variety of waveguiding device applications.