Spatially resolved thermal characterization of packaged vertical cavity surface-emitting lasers

The experimental thermal characterization of ion implanted vertical cavity surface-emitting lasers (VCSELs) and their own packages was carried out by means of an enhanced version of the thermal resistance analysis by induced transient (TRAIT) based on the analysis of the heat source temperature transients. This technique allowed the measurement of the thermal resistance of the device-package system with a spatial resolution so that the heat conduction properties of all the parts of the structure were separately and directly evaluated. The increased time and temperature resolution of the experimental measuring set-up allowed us to calculate up to 12 rows of the time constant spectrum and therefore to obtain equivalent thermal circuits with 12 resistance-capacitance low-pass cells. The experiments performed on packaged devices from different manufacturers enabled us to identify the origin of possible critical points of the assembling structures, despite their negligible contributions to the total thermal resistance in comparison to those of the semiconductor chip. The experimental results were also found to be in agreement with the data obtained using analytical models for the calculation of the thermal resistance in such laser devices.