A thermomechanical model to explain the formation of dark defects in AlGaAs high power laser bars is presented. The local heating at facet defects due to nonradiative recombination and self-absorption of photons induces thermal stresses capable of producing a local plastic deformation and subsequent degradation of the device. The output power density thresholds calculated are in agreement with the data reported in the literature for these lasers.

In this work we study the defects responsible for the degradation of high power AlGaAs based laser bars. The mirror and cavity degradations are studied by spectral cathodoluminescence (CL) imaging. Following the analysis of the CL images the main defects generated during the laser operation are revealed, both facet and intracavity defects are observed. A thermomechanical model is used to describe the very beginning of the defect formation. The defects are formed by a local plastic deformation induced by local heating at defects.

High-power semiconductor lasers are required to be more and more powerful, efficient and reliable for applications such as solid-state lasers pumping, materials processing, and thermal printing among others. The understanding of the degradation mechanisms is essential to improve the high power laser reliability. The highest power emission is achieved with multi-emitter laser cm-bars, which present problems related to packaging induced stress. A very harmful defect in this type of devices is the so-called V defect. We present herein a study of these defects using cathodoluminescence imaging, the role of packaging is discussed.

We have investigated the mid-infrared spontaneous and stimulated emission between confined subbands in the conduction band of GaAs/AlGaAs quantum wells. The carriers which give rise to the intersubband emission are excited in the upper subbands using an intersubband optical pumping in coupled asymmetric quantum wells. The quantum wells are designed using phonon engineering in order to obtain population inversion between the second and first excited subband. This is obtained by adjusting the subband energy spacing between E2 and E1 close to the optical phonon energy which in turn allows an efficient relaxation. We have first observed intersubband spontaneous emission between E3 and E2 at 14 μm using an intersubband pumping with a CO2 laser in resonance with the E1-E3 transition. In a second set of experiments, the quantum wells are embedded in an infrared waveguide. We have measured the stimulated intersubband gain using a picosecond two-color free electron laser. The first color bleaches the E1-E3 transition and provides the population inversion. The intersubband stimulated gain is measured versus the waveguide length and photon energy. Stimulated gains ≈ 80 cm−1 are reported thus demonstrating that laser emission under optical pumping appears feasible in optimized structures. Finally, we show that intersubband emission can also be observed in quantum wells using an interband optical pumping.