Coupling of optical modes in GaN‐based laser‐diodes

The optical waveguiding in GaN-based laser-diodes grown on sapphire substrates is investigated. Modes mainly guided either in the GaN buffer layer or between the AlGaN cladding layers interact with each other. This results in minima of the confinement factor at periodic intervals of the buffer layer thickness and in a multi-peak far field distribution. It is shown that the mode coupling can hardly be suppressed by a variation of either the thickness or the composition of the AlGaN cladding layers. Instead, the use of an AlGaN buffer layer or an InGaN waveguide is suggested. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)