Optical Absorption Rate Determination, on the Front Facet of High-Power GaAs Laser Diodes, by Means of Thermoreflectance Technique

Very-high-resolution thermoreflectance measurements have been used to study the light absorption occurring on the front facet of GaAs laser diodes, which is responsible for their damage. We determined the activation of the induced surface heat source for an injected current higher than the laser emission threshold current. This varying thermal behavior of the laser diode according to the value of the injected current has been used to determine the contribution to heat dissipation due to the surface source only. By identification using a thermal model we could evaluate for the first time the surface absorption rate both on coated and noncoated laser diodes. We propose it as a new reliability criterion, which enables discrimination of laser diodes both according to their coating and to their aging.