Rotation of principal axes and birefringence in III-V lasers owing to bonding strain.

Measurements of the degree of polarization (DOP) of photoluminescence from the facets of bonded III-V semiconductor diode laser chips show shear strain. The effect of shear strain on the refractive index is investigated. Finite element method (FEM) simulations are matched to the facet map of the DOP for a bonded GaAs chip and are used to extract estimates of the strain induced by die attach. Given estimates of the strains from the FEM simulations, changes in the refractive indices and rotations of the principal axes are calculated for the chip. This work has value in understanding operational changes owing to bonding-induced strain.