The　phenomenon　of　transient　and　long-term　COD　was　studied　experimentally　by　means　of　thermal　infrared　imaging,　laser　scanning　confocal　microscopy,　and　transient　thermal　technique.　The　long-term　COD　occurs　in　practical　operation　of　high　power　laser　diode,　and　the　melting　spots　were　observed　in　output　facet,　as　well　dark　line　defects　appeared　in　cavity　of　high　power　laser　diodes.　Meanwhile,　the　transient　COD　occurred　with　the　input　current.　We　have　recorded　the　dynamics　of　COD　process　using　thermal　infrared　camera.　The　temperature　of　transient　COD　has　a　sudden　increase　of　32.07　degrees　C　when　the　COD　event　occurs　which　maintains　less　than　8.69　ms.　It　was　found　that　the　thermal　resistance　of　chip　increases　remarkably　after　COD,　meanwhile　the　thermal　resistance　of　solder　and　package　does　not　change　apparently.