A study has been made of wavelength tuning in double heterostructure InAsSb/InAsSbP-based diode lasers. A simple mathematical model, which takes into account the spatially homogeneous injection and the dependence of the dielectric constant on the charge carrier density, is discussed. The wavelength can be increased or decreased, depending on the pump current and diode structure parameters, as is observed experimentally. The process of wavelength tuning proceeds with virtually zero delay time since it is determined by the photon lifetime in the cavity and in part by the lifetime of nonequilibrium charge carriers.