Spectroscopic measurement of mounting-induced strain in optoelectronic devices

Mounting-induced strain in high-power laser diodes is studied by noninvasive photocurrent (PC) spectroscopy. We demonstrate that the strain can be determined with high accuracy by means of Fourier-transform (FT) photocurrent measurements. The optical transitions within the quantum well (QW) region of identical InAlGaAs/GaAs laser diodes which were mounted with different external strain have shown spectral shifts of up to 10 meV. The accuracy of the energy level shifts obtained by FT PC measurements is of 150 ? eV for the QW-region and 500 ?eV for the waveguide region. The measured strain status of the active region is compared with model calculations to quantify the amount of strain which is transferred from the heat sink to the semiconductor device.