A novel theoretical model of thermal diffusion has been established to study thermal interaction between two neighboring diodes in semiconductor laser arrays. The main cause of the ocurrence of the thermal interaction between two neighboring diodes in array devices is the heat conduction through heat sink. We hold that as the devices must have heat sink to diffuse heat, this kind of interaction in the array would always exist. However, when the pitch between two neighboring diodes in the array is reasonably defined, this troublesome thermal interaction can be simply reduced by using our model. Based on the individual diodes with leaky waveguide structure, we experimentally succeeded in fabricating 2D 4×4 arrays. The thermal interaction between upper and lower diodes in the 2D array is also considered as well as the function of the heat sink. The measured results show that the pulse peak output power of the 2D 4×4 array is high up to 11 W.