This study investigated the effect of thermal management on the performance of vertical-cavity surface-emitting lasers (VCSELs). It was found that the thickness of silicon substrate, which can serve as the submount for VCSEL packages, has a strong influence on the thermal dissipation of on-chip laser sources, and eventually impacts on their output characteristics. Moreover, the improvements in optical characteristics of the on-chip VCSELs were the best heat dissipation through thinning silicon substrates to 50- $\mu \text{m}$ thickness combined with electroplated Cu with 100- $\mu \text{m}$ thickness. In addition, this study also performed COMSOL simulations. The simulation results were consistent with experimental results.