Composite phase-based metasurfaces for the generation of spin-decoupling orbital angular momentum single-photon sources

Solid-state quantum emitters, such as semiconductor quantum dots (QDs), have numerous significant applications in quantum information science. While there has been some success in controlling structured light from kinds of single-photon sources, the simultaneous on-demand, high-quality, and integrated generation of single-photon sources with various degrees of freedom remains a challenge. Here, we utilize composite phase-based metasurfaces, comprising transmission phase and geometric phase elements, to modulate the semiconductor QD emission through a simplified fabrication process. This approach enables to decouple the emission into left and right circularly polarized (LCP/RCP) beams in arbitrary directions (e.g., with zenith angles of 10° and 30°), producing collimated beams with divergence angles less than 6.0° and carrying orbital angular momentum (OAM) modes with different topological charges. Furthermore, we examine the polarization relationship between the output beams and QD emission to validate the performance of our designed devices. Additionally, we achieve eight channels of single-photon emissions, each with well-defined states of spin angular momentum (SAM), OAM, and specific emission directions. Our work not only demonstrates an effective integrated quantum device for the on-demand manipulation of precise direction, collimation, SAM, and various OAM modes, but also significantly advances research efforts in the quantum field related to the generation of multi-OAM single photons.