Abstract

We report on a DFB laser technology for GaAs based lasers. Such a structure is normally problematic to achieve due to overgrowth on Al containing layers. Current approaches to achieve DFB on GaAs are laterally loss coupled gratings [1], which are not suitable for manufacturing, or Al-free structures [2] which require precise stochiometric control of the InGaP, and lack the design flexibility available using AlGaAs. Our technique is to use an InGaP/GaAs grating layer in conjunction with AlGaAs cladding layers, where the AlGaAs is never exposed to air. Due to the high refractive index contrast of InGaP/GaAs, the grating layer is ~450nm from the active layer, which helps in minimising any deleterious effects of the re-growth process on laser performance. The epitaxial structure was designed by modelling confinement factors in a commercial refractive index mode solver, Fimmwave [3].

© 2009 IEEE