Micro-Temperature Measurements on Semiconductor Laser Mirrors by Reflectance Modulation: A Newly Developed Technique for Laser Characterization

Thermoreflexance measurements performed for the first time on laser diode mirrors have supplied a vast amount of novel information. Heating efficiency has been found to depend sensitively on the mirror treatment, the mirror structure design, the geometry of a deposited heat spreader, the type of coupling of the laser to a heat sink, the number of active quantum wells, the type of cladding layer and the strength of lattice disorder at the mirror surfaces. Degradation processes have been observed in real time by continuously monitoring the mirror temperature. Dark line defects formed during laser operation exhibit a temperature gradually increasing with time. The mirrors suffer catastrophic optical damage within seconds after having reached a critical temperature. Temperature maps show a striking localized hot spot within the optical near-field pattern.