Thermal Equivalent Circuit Model for Coupled-Cavity Surface-Emitting Lasers

In this paper, for the first time, an equivalent circuit model, including temperature effects, is introduced for coupled-cavity vertical cavity surface-emitting lasers (CC-VCSELs). This model is based on a set of coupled rate equations for two carrier concentrations, a single longitudinal optical mode, and the temperatures of the cavities. By considering the main intrinsic physical processes inside the active layer, we modified the standard coupled rate equations to account for the effects of both the thermal-dependent laser gain and active layer carrier leakage current on CC-VCSELs performance. The presented model can be used in general purpose circuit simulators to study the influence of the thermal dependence of the laser gain spectrum, cavity resonance modes, and carriers leakage currents on the light-current (L-I) characteristics under different biasing conditions with a reasonable accuracy. Simulations results show that the threshold characteristic and linearity of the L-I curve are severely related to the temperature. On the other hand, the temperature variations cause the output optical power rollover. In addition, we verify that the variations of the threshold current with temperature have a parabolic form. Our results are in good agreement with the reported experimental data.