Fiber coupled laser diode reliability: impact of feedback on diode lifetime and failure modes

We present results of an extensive study on broad area lasers (BALs) with different antireflection (AR) coatings in the wavelength range from 780 nm to 1020 nm, which have been investigated under external optical feedback (EOF) to detect reversible and irreversible impacts caused by back-reflected laser radiation. The observation of the near-field (NF) distribution vs. injection current gave us information about filamentation and peak-power densities with and without EOF. Depending on the emission wavelength of the BALs, there are different energy absorption (heating) scenarios leading to different failure modes. For GaAs-based laser diodes, the energy gap of the substrate material makes the distinction at a wavelength of ~870 nm.