Uniaxial stress flips the quantization axis of a quantum dot for integrated quantum photonics

Abstract

The selection rules of optical transitions in epitaxial quantum dots are determined to a large extent by the orientation of their quantization axis, which is usually parallel to the growth direction. This configuration is well suited for single-photon sources embedded in vertically emitting devices, but not ideal for planar photonic circuits because of the poorly controlled orientation of the transition dipoles in the growth plane. Here we show that, for relatively large and initially unstrained GaAs dots, the quantization axis can be flipped to lie in the growth plane via moderate in-plane uniaxial stress. By using piezoelectric strain-actuators featuring strainamplification we study the evolution of the selection rules and excitonic fine-structure in a previously unexplored regime, in which quantum confinement can be seen as a perturbation compared to strain in determining the symmetry-properties of the system. The experimental and computational results suggest that uniaxial stress – already employed for enhancing the performance of integrated electronic circuits – may be the right strategy to obtain quantum-light sources with ideally oriented transition dipoles and enhanced oscillator strengths for integrated quantum photonic circuits.