Fig. 3.

Rotation of natural quantization axis under uniaxial stress along [100]. a–d Color-coded linear polarization-resolved PL spectra of a GaAs QD for increasing tensile stress (a, b) and selected spectra along orthogonal polarization directions (c, d). The polarization angle φ is referred to the [100] crystal direction. Initially, a, c the emission from the neutral exciton X and multiexcitons MX shows no significant net polarization and the X emission is characterized by two bright components linearly polarized along orthogonal but random directions (~30° and ~120° for this QD). This random orientation stems from slight anisotropy in the confinement potential defined by the QD and also from some process-induced prestress. At large stress, b, d the PL is almost fully polarized along the [010] direction (φ* = 90°). e Evolution of the degree of linear polarization of X emission and MX “band” (emission between vertical dashed lines in a and b for increasing tensile stress (increasing magnitude of applied electric field on actuator). f Evolution of polarization orientation φ* for the MX band and for the high-energy component of the X line for varying stress