Photocurrent spectroscopy is applied for an analysis of both packaging-induced strain and strain-induced defect creation in InAlGaAs/GaAs high-power diode laser arrays. Strain profiles across 50 W diode lasers processed by different packaging procedures are measured and compared to model calculations. We demonstrate that packaging-induced strain giving rise to spectral shifts of the laser transition correlates with packaging-induced defects in the waveguide that are quantified via a sub-band gap absorption band. Packaging on a Cu–diamond multilayer heat spreader appears as optimized solution simultaneously minimizing strain and defect creation.

We present a strategy for quantitative spectroscopic analysis of packaging-induced strain using both finite element analysis and band-structure calculations. This approach holds for a wide class of AlGaAs-based, and related, devices, among them high-power “cm-bars.” The influence on the results of particular device structure properties, such as intrinsic strain and quantum-well geometry, is analyzed. We compare theoretical results based on a unaxial stress model with photocurrent data obtained from an externally strained cm-bar, and obtain better agreement than from alternative strain models. The general approach is also applicable to the analysis of all data that refer to changes of the electronic band structure, such as absorption and photoluminescence.

The transient thermal properties of high-power diode laser bars with active and passive cooling are analyzed. Both thermal imaging and the analysis of the thermal wavelength tuning behavior are employed to extract the device temperature as a function of time. A steady-state thermal situation is established with rise times of about 10 and 60ms for active and passive cooling, respectively. The latter number, however, is substantially increased by the particular properties of the external heat sink. Such results are confirmed by model calculations based on the finite element method.

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Thermally induced strain caused by device packaging is studied in high-power semiconductor lasers by a noninvasive technique. Fourier-transform photocurrent measurements with intentionally strained laser array devices for 808 nm emission reveal spectral shifts of quantum-confined optical transitions in the optical active region. These shifts by up to 7 meV serve as a measure for strain and are compared with model calculations. For a given packaging architecture, about one quarter of the mounting-induced strain is transferred to the quantum-well region of the device. Spatially resolved measurements demonstrate a lateral strain gradient in the devices.

High power laser diodes and especially high power laser diode modules made enormous progress in the last few years. Different aspects of high power laser diodes are treated starting from general description of high power laser diodes and their mounting techniques, characterising the electro-optical behaviour of single laser bars and finally presenting beamshaping optics for the collimation of large modules. The later technique allows for symmetrical focal spots in the kilowatt range with a beam quality of about 170 mm*mrad. Different aspects of current applications of high power laser diodes are presented.

Packaging-induced strain is studied in high-power semiconductor lasers by a noninvasive optical technique. Fourier-transform photocurrent measurements with intentionally strained laser array devices for 808 nm emission reveal spectral shifts of optical transitions within the active region. These shifts by up to 10 meV serve as a measure for the strain status within the active layer of the devices and are compared with model calculations. For different packaging architectures we quantify the strain portion which is transmitted to the optically active region of the semiconductor device.

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