Abstract

Because of their cylindrical symmetry and surface emission, the material gain and waveguiding anisotropies in VCSELs are small. As a result, polarisation switching (PS) between two orthogonal linearly polarised states is often observed. We study experimentally the effect of in-plane uniaxial strain, resulting from an external stress applied to the VCSEL package. We used proton-implanted GaAs'AlGaAs quantum-well VCSELs operating around 850nm at the higher frequency side of the gain maximum (substrate temperature 25°C). A tensile uniaxial strain is introduced in VCSEL cavity by bending the metal plate on which the wafer is glued I he polarization resolved light vs current characteristics are presented in fig 1 for different magnitudes of the tensile strain along [1-10] (1a) and [110] directions (1b). Depending on the relative orientation of the strain and the crystal coordinates, PS from the lower to the higher frequency mode (PS type II) can take place, or not, for one and the same birefringence Δv - compare (a) to (b) in fig 1. Furthermore, the PS current could be strain-tuned in the entire region of the fundamental mode for the strain along [1 -10] (fig. 1 a) but not for the strain along [110] (fig 1b).

© 2000 IEEE