The　degradation　of　AlGaAs/GaAs　laser　diodes　is　studied　in　detail　using　laser　scanning　confocal　microscopy,　cathodoluminescence　images,　and　x-ray　diffraction　(XRD)　techniques.　Our　analysis　has　identified　a　degradation　mechanism　that　results　from　the　periodic　distribution　of　the　carrier　density　and　the　near-field　intensity　originating　from　periodic　spatial　hole　burning.　Based　on　the　XRD　measurements,　we　find　that　the　epitaxial　layer　enters　a　polycrystalline　phase　during　degradation　due　to　the　dark　line　defects,　and　the　out-of-plane　strain　and　in-plane　compressive　stress　are　induced　by　degradation.　(C)　2011　American　Institute　of　Physics.　[doi:　10.1063/1.3634051]