The　thermal　properties　of　AlGaAs/GaAs　laser　diode　bars　have　been　analyzed　in　detail　by　transient　thermal　technique　based　on　the　diode　forward　voltage　method　on　the　vertical　and　horizontal　thermal　conduction　paths,　respectively.　On　the　vertical　thermal　conduction　path,　it　is　found　that　the　steady-state　temperature　rise　of　the　central　emitter　among　operated　emitters　has　a　linear　relationship　with　the　logarithm　of　the　total　operating　current.　The　time　constant　determined　for　chip　decreases　with　the　total　operating　current,　while　the　time　constant　determined　for　solder/heat　sink　interface　and　package　remains　almost　constant.　In　addition,　the　effective　thermal　diffusivity　of　chip　increases　with　total　operating　current.　On　the　horizontal　thermal　conduction　path,　the　time　constant　varies　linearly　with　the　distance　increasing,　and　the　effective　thermal　diffusivity　remains　almost　constant.　The　results　suggest　that　the　thermal　crosstalk　between　emitters　increases　with　the　total　operating　current.　(C)　2012　Elsevier　Ltd.　All　rights　reserved.