Observation of changes of laser beam characteristics in aged oxide-defined narrow-stripe lasers

Aged oxide-defined narrow-stripe lasers sometimes exhibit beam narrowing in both the near-field and far-field light distributions, accompanied by the development of sustained pulsations. The beam narrowing is found to correlate with the presence of a darkened area under the stripe viewed by cathodoluminescence imaging. We propose an explanation based on a thermal waveguiding effect resulting from increasing heat dissipation in the darkened area.