An analytical three-dimensional thermal model is employed to perform the thermal design for the package of high-power single-emitter laser diodes. Thermal design curves for the heat sink and submount are presented in detail, for laser diodes subjected to several convective heat transfer conditions on the bottom of the heat sink. An effective heat spreading angle is proposed to characterize thermal design for the heat sink. A differential heat spreading angle is proposed to clearly manifest heat flow in the packages. Full width and length at 90% energy are introduced to reveal the requirement of submount width and length, respectively. The impact of coefficient of thermal expansion (CTE)-matched sandwiched submount on total heat dissipation is studied. Special discussion is presented for a commercial F-Mount laser diode, and it is found that current heat sink design leads to a 27.4% increase in thermal resistance relative to a free lateral diffusion package. © 2020 Elsevier Ltd