  In this study, we examine a photonic wire waveguide embedded with an ensemble
of quantum dots that directionally emits into the waveguide depending on the
spin state of the ensemble. This is accomplished through the aid of the
spin-orbit interaction of light. The waveguide has a two-step stair-like cross
section and embeds quantum dots (QDs) only in the upper step, such that the
circular polarization of emission from the spin-polarized QDs controls the
direction of the radiation. We numerically verify that more than 70% of the
radiation from the ensemble emitter is toward a specific direction in the
waveguide. We also examine a microdisk resonator with a stair-like edge, that
supports selective coupling of the QD ensemble radiation into a whispering
galley mode rotating unidirectionally. Our study provides a foundation for
spin-dependent optoelectronic devices.
