Spatially resolved spectroscopic strain measurements on high-power laser diode bars

We compare a number of strain-sensitive spectroscopic techniques, namely, micro-Raman, micro-photoluminescence, photocurrent, and electroluminescence by applying them to two AlGaAs/GaAs high-power diode laser arrays, so-called “cm-bars.” Both devices are fabricated from the same bar batch and considered “identical,” but experienced two different packaging procedures that resulted in different intentionally adjusted “packaging-induced” compressive strains along the array, namely, about −(3.0±0.5)×10−4 and −(5.0±0.7)×10−4 strain difference between edges and centers of the bars. The methods are primarily evaluated with respect to their ability to monitor and quantify the different spatial strain distributions along the devices. In addition their potential for defect detection is demonstrated. Pros and cons of the techniques are summarized and discussed.