Thermoreflectance-Based Measurement of Facet Optical Absorption in High Power Diode Lasers

Severe heating due to partial absorption of outcoupled emission at the facet of a high-power diode laser can lead to catastrophic optical damage. The degree of absorption and subsequent heating at the facet is a function of the emission wavelength, the absorption properties of facet coatings and passivation layers, and the age of the device. The ability to quantify facet absorption is an essential step toward improving the reliability and maximum output power of diode laser systems. In this work, we have developed a technique to measure facet absorption in diode lasers using a combination of facet thermoreflectance imaging and a heat transport model. The approach can be used for a wide range of both coated and uncoated diode lasers.