The　transient　thermal　characteristics　related　to　catastrophic　optical　damage　(COD)　in　high　power　AlGaAs/GaAs　laser　diodes　(LDs)　are　studied　experimentally　by　means　of　thermal　infrared　imaging,　laser　scanning　confocal　microscopy,　and　transient　thermal　technique.　The　transient　thermal　technique　is　based　on　the　diode　forward　voltage　method　in　which　the　structure　function　theory　is　applied　to　determine　the　component　thermal　resistance　and　temperature　rise　of　the　LDs.　We　have　recorded　the　dynamics　of　COD　process　using　thermal　infrared　camera.　Two　melting　spots　are　observed　in　the　output　facet　after　COD　which　location　exactly　matches　the　position　of　the　thermal　flash　from　the　thermal　imaging　and　even　the　temperature　of　COD　seed　has　a　sudden　increase　of　32　K　when　the　COD　event　occurs.　Furthermore,　we　find　that　the　thermal　resistance　from　chip　to　In　solder　increases　remarkably　after　COD,　meanwhile　the　thermal　resistance　of　solder　and　package　does　not　change　apparently.　The　results　are　attributed　to　the　heat　power　dissipation　increase　originating　from　the　enhancement　of　nonradiative　recombination　after　COD　under　constant　input　electrical　power.　(C)　2013　WILEY-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinheim