Defect recognition via longitudinal mode analysis of high power fundamental mode and broad area edge emitting laser diodes

A nondestructive method is presented which allows a precise detection of de fects and their positions inside the cavity of semiconductor lasers. The de fect recognition is based on the measurement of the longitudinal mode spect rum below threshold and the inspection of its Fourier transformation. Using a theoretical model, it is shown that a small distortion inside the cavity leads to a peak in the Fourier transformed spectrum from which the positio n of the distortion relative to the facets can be determined. For a ridge w aveguide laser we find a direct correlation between defects identified by t he analysis of the longitudinal mode spectrum and cathodoluminescence imagi ng. The applicability of this method for nondestructive defect recognition will also be demonstrated for broad area laser diodes with lateral multimod e emission. The investigations reveal that the presented method can be used to assess the crystal quality of manufactured laser diodes. (C) 2001 Ameri can Institute of Physics.