Directional nanophotonic atom--waveguide interface based on spin-orbit coupling of light
Author(s): R. Mitsch, C. Sayrin, B. Albrecht, A. Rauschenbeutel
Journal: arXiv: quant-ph
DOI Number: -
Link: Link to publication
Optical waveguides in the form of glass fibers are the backbone of global telecommunication networks. The physical principle enabling the transmission of light over long distances is total internal reflection which occurs at the interface between two media with different refractive indices. Although this mechanism ensures that no light escapes from the waveguide, there is always an evanescent field that penetrates into the optically thinner surrounding medium. While this field is protected from interacting with the environment in standard optical fibers, it is routinely employed in order to efficiently couple light fields to optical components or emitters using, e.g., prisms or tapered optical fiber couplers. Remarkably, the strong confinement imposed by the latter can lead to significant spin--orbit coupling. Taking advantage of this effect, we demonstrate the controlled directional spontaneous emission of light by quantum emitters into a sub-wavelength-diameter waveguide. The effect is investigated in a paradigmatic setting, comprising cesium atoms as the emitters which are located in the vicinity of a vacuum-clad silica nanofiber. We experimentally observe an asymmetry higher than 10:1 in the emission rates into the counterpropagating fundamental guided modes of the nanofiber. Moreover, we demonstrate that this asymmetry can be tailored by state preparation and suitable excitation of the quantum emitters. We expect our results to have important implications for research in nanophotonics and quantum optics and for implementations of integrated optical signal processing in the classical as well as in the quantum regime.