Reflectance Modulation Studies On Laser Diode Mirrors

The versatility and usefulness of the newly developed reflectance modulation technique for laser mirror characterization will be demonstrated by means of typical examples of application on (110) facets of 10-mu-m wide ridge waveguide AlGaAs/GaAs quantum well lasers: (1) Typical, maximum temperature increases DELTA-T derived from the reflectance changes DELTA-R/R are congruent-to 1 K per 1 mW optical diode power for uncoated mirrors and are congruent-to 10x lower for lambda/2-Al2O3 coated ones. DELTA-T is sensitive to the facet surface treatment prior to coating. (2) Temperature maps show a very localized hot spot within the near-field region and are in accordance with our two-dimensional heat flow calculations. (3) Degradation processes have been monitored in real time. Thus, we determined a critical temperature increase DELTA-T congruent-to 120 K for the occurrence of catastrophic optical mirror damage in the AlGaAs system.