Thermal imaging and quantitative modelling of a laser diode for optical network communications

Using infrared thermography, we have carried out a detailed characterization of the thermal properties of a laser module for optical telecommunications. In association with the measurement of thermal properties of its constitutive materials and thermoreflectance temperature imaging, this allowed us to validate a complete finite element-based model of the complete laser module, with its active Peltier cooling. The good correlation between simulation and measurements allows us to numerically explore the thermal transfer mechanisms of this active device, and predict optimized combinations of materials and architectures. The Peltier cooler device is responsible for a large portion of the total electrical consumption of the module. It turns out that the precision of the characteristics given by suppliers is not sufficient to achieve sufficient precision. Its main thermal contact with the environment is achieved through a metallic baseplate currently used in such packages (a FeNiCo alloy subsequently called Kovar ®). We therefore conducted a full thermal and electrical characterization of a naked Peltier with or without its baseplate, and separated from the rest of the laser module. This allowed us to describe the inbound (QC) and outbound (QH)thermal power flows in the Peltier :