By performing a full analysis of the projected local density of states (LDOS) in a photonic crystal waveguide, we show that phase plays a crucial role in the symmetry of the light-matter interaction. By considering a quantum dot (QD) spin coupled to a photonic crystal waveguide (PCW) mode, we demonstrate that the light-matter interaction can be asymmetric, leading to unidirectional emission and a deterministic entangled photon source. Further we show that understanding the phase associated with both the LDOS and the QD spin is essential for a range of devices that can be realized with a QD in a PCW. We also show how suppression of quantum interference prevents dipole induced reflection in the waveguide, and highlight a fundamental breakdown of the semiclassical dipole approximation for describing lightmatter interactions in these spin dependent systems.

Phys. Rev. Lett.

Young, A. B., Thijssen, A. C. T., Beggs, D. M., Androvitsaneas, P., Kuipers, K., Rarity, J. G., … Oulton, R. (2015). Polarization Engineering in Photonic Crystal Waveguides for Spin-Photon Entanglers. Phys.Rev.Lett., 115(Article number: 153901), 1–5. doi:10.1103/PhysRevLett.115.153901