Spin-dependent directional emission from a quantum dot ensemble embedded in an asymmetric waveguide.

In this study, we examine a photonic wire waveguide embedded with an ensemble of quantum dots (QDs) that directionally emits into the waveguide depending on the spin state of the ensemble. The directional emission is facilitated by the spin-orbit interaction of light. The waveguide has a two-step stair-like cross section and QDs are embedded 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, which supports selective coupling of the QD ensemble radiation into a whispering gallery mode that rotates unidirectionally. Our study provides a foundation for spin-dependent optoelectronic devices.