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. ©1998 American Institute of Physics.