Analysis of thermal images from diode lasers: Temperature profiling and reliability screening

Abstract

Imaging thermography in the 3-5 μm wavelength range is applied to the analysis of thermal properties of high-power diode lasers. We investigate these devices by inspecting their front facets as well as their active regions along the resonator. The latter is done through top windows within the substrate. Raw data are found to be mostly interfered by thermal radiation traveling through the substrate, which is transparent for infrared light. Substracting this contribution and recalibration allows for obtaining realistic temperature profiles along laser structures. Facet heating is analyzed complementary by micro-Raman spectroscopy. We show how hot spots at the front facet, in the substrate, or even in the active region within the substrate are discovered. Our approach paves the way for an advanced methodology of device screening. © 2005 American Institute of Physics.