Thermal Characterisation of Hybrid, Flip-Chip InP-Si DFB Lasers

WA detailed thermal analysis of a hybrid, flip-chip InP-Si DFB laser is presented in this work. The lasers were experimentally tested at different operating temperatures, which allowed for deriving their thermal performance characteristics: the temperature dependence of threshold current, lasing slope, and output spectrum. Using these data, the laser thermal resistance was calculated (R_th = 75.9 K/W), which allows for predicting the laser temperature during operation. This metric is also used to validate the thermal finite element models of the laser. A sensitivity study of the laser temperature was performed using these models, and multiple routes for minimising both the laser thermal resistance and thermal coupling to the carrier die are presented. The most effective way of decreasing the laser temperature is the direct attachment of a heat sink on the laser top surface.