Influence of mounting stress on polarisation degree of electroluminescence of laser diode bars

Summary form only given. Efficient high power laser diode bars emitting in the wavelength range around 800 nm have a great future as pump sources for solid state lasers, for direct material processing and in medicine. For a wider use of laser bars it is necessary to increase the maximum output power and to improve the long-term reliability of the devices. The unmounted laser diode bars are not flat-they show a "smile". That leads to an additional strain in the structure due to the mounting process. Because it is very difficult to minimise this "smile", it is important to investigate its influence on the device properties. In this paper, measurements of the polarisation-resolved electroluminescence below threshold (indicating bulk properties) and the threshold currents of the individual emitters of laser bars are presented. By this means, strong changes in the strain distribution before and after mounting and after aging can be detected. Laser diode bars having 24 emitters (200 /spl mu/m aperture width, 50% filling factor, 1 mm cavity length, tensile-strained GaAsP quantum well embedded in AlGaAs waveguiding and cladding layers) emitting at 808 nm are used. They were mounted p-side down on conductively cooled heat sinks.