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Room-temperature emission is observed as long as 3.26 μm in optically pumped type-I quantum well lasers on relaxed epitaxial layers grown by molecular-beam epitaxy. A superlattice is used to filter dislocations in the metamorphic buffer to reduce Shockley–Read–Hall losses. The longest wavelength emission of 3.45 μm from these structures is observed at 170 K, and the brightest room-temperature laser emits 0.5 W/facet peak power at 2.81 μm. It has a low threshold power density of 169 W/cm2 and a differential quantum efficiency of 28%. The characteristic temperatures, T0 and T1, are 119 K and 171 K, respectively. Stimulated emission is observed in this sample at a maximum operating temperature of 370 K.

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A theoretical framework for the analysis of the stress distribution in granular materials is presented. It makes use of a transformation of the vertical spatial coordinate into a formal time variable and the subsequent study of a generally non-Markoffian, i.e., memory-possessing ͑nonlocal͒ propagation equation. Previous treatments are obtained as particular cases corresponding to, respectively, wavelike and diffusive limits of the general evolution. Calculations are presented for stress propagation in bounded and unbounded media. They can be used to obtain desired features such as a prescribed stress distribution within the compact.

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