Direct spectroscopic measurement of mounting-induced strain in high-power optoelectronic devices

Abstract

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.

Spectroscopic analysis of external stresses in semiconductor quantum-well materials

“…1 (b), and/or by making measurements while employing excitation with polarized light, cf. [5]. Furthermore, there are much weaker bands energetically below the QW absorption edge.…”

“…Fourier-transform (FT) spectroscopy significantly improves the quality of PC spectra measured [1,5]. The setup remains the same as for a FT-based transmission measurement, but the regular sample is replaced by the laser diode that will be analyzed.…”

“…There are several experimental techniques suitable for spectroscopic strain analysis, such as Raman [2], photoluminescence [3,4], and photocurrent (PC) spectroscopy [5]. We use the PCtechnique and introduce its background in the section on experimental details.…”

Screening of high power laser diode bars in terms of stresses and thermal profiles

“…1 (b). 5 Of course, these transition energies might depend (except on the packaging-induced strain) on additional parameters such as, e.g., thickness-and compositionhomogeneity of the epitaxial layers. In order to minimize the influence of this type of sample homogeneity, we consider information from two physically different positions within the epilayer sequence, namely from QW and waveguide.…”

Spatially-resolved spectroscopic strain measurements at high-power diode laser bars

“…Refs. [1,2], which is directly soldered onto the Cu heat sink. Note the excellent agreement of the Aa/a(x)-curves from QW and waveguide that act as independent 'strain-sensors'.…”