Junction temperature/thermal- resistance is reflected in the comprehensive cooling capacity of laser devices, which is closely related to the sintering quality of the solder layer. The operating junction temperatures of laser devices have been detected by the forward-voltage and wavelength-shift methods. The distribution of voids in the solder layer have been analyzed using a scanning acoustic microscope. The results verify the feasibility of junction temperature measurement, and confirm the relation between the junction temperature and the sintering quality of laser chips. These results will pave the way for the development of semiconductor lasers and the filtering of laser devices.