Effects of transverse mode coupling and optical confinement factor on gallium-nitride based laser diode

We have investigated the transverse mode pattern and the opticalfield confinement factor of gallium nitride (GaN) laser diodes (LDs)theoretically. For the particular LD structure, composed ofapproximate 4 $mu $m thick n-GaN substrate layer, the maximumoptical confinement factor was found to be corresponding to the5$^{rm th}$ order transverse mode, the so-called lasing mode.Moreover, the value of the maximum confinement factor variesperiodically when increasing the n-side GaN layer thickness, whichsimultaneously changes and increases the oscillation mode order ofthe GaN LD caused by the effects of mode coupling. The effects ofthe thickness and the average composition of Al in the AlGaN/GaNsuperlattice on the optical confinement factor are also presented.Finally, the mode coupling and optimization of the layers in theGaN-based LD are discussed.