A　1.3　GHz　repetition　rate　optically　pumped　passively　mode-locked　semiconductor　disk　laser　with　5.5　ps　pulse　duration　and　204　mW　average　output　power　at　978　nm　wavelength　was　demonstrated.　Main　factors　preventing　the　mode-locked　laser　from　higher　output　power,　such　as　the　epitaxy　structure　of　wafer　and　thermal　characteristics　of　gain　chip　were　investigated,　and　corresponding　methods　to　improve　the　thermal　performance　of　the　laser,　e.g.,　growing　the　wafer　in　a　reversed　sequence,　removing　substrate　entirely　and　using　a　diamond　as　heat　spreader,　were　proposed.　The　experimental　results　showed　that　both　the　microcavity　mode　of　laser　and　the　emission　wavelength　of　QWs　redshifted　when　the　pump　power　increased,　but　their　redshift　rates　were　different.　This　suggested　us　to　consider　a　pre-offset　between　the　emission　wavelength　of　QWs　at　room　temperature　and　the　target　wavelength　of　laser　at　an　intense　pump,　and　the　pre-offset　values　of　the　wavelength　should　be　designed　deliberately　to　guarantee　the　resonant　periodic　gain　structure　working　properly　when　the　temperature　in　the　active　region　approaches　the　desired　value.