As high-power laser diodes continue to make advances in various photonic applications, it is all the more important to understand the phenomena that can lead to lower outputs and lifetimes. A team at Max Born Institut für Nichtlineare Optik und Kurzzeitspektroskopie in Berlin and Jenoptik Laserdiode GmbH in Jena, Germany, has employed photocurrent spectroscopy to quantify strain and defect formation simultaneously in a 1-cm-wide bar of InAlGaAs/GaAs lasers.

The scientists, who published their findings in the Oct. 21 issue of Applied Physics Letters, collected the photocurrent spectra using a Fourier transform spectrometer. They discovered that the strain that accompanies cooling of the solder produces a spectral shift in the optical transitions related to the quantum wells, which they confirmed using micro-Raman spectroscopy.

The photocurrent spectra also are indicative of defect concentration, they found.