Subwavelength optical guiding for coupling cold atoms to a nanophotonic microring resonator

Cold atoms trapped and interfaced with guided light in nanophotonic circuits form exciting new platforms for fundamental research on atom-light interactions and applications in quantum optics, quantum many-body physics and quantum networks. Experimental demonstrations to date have primarily focused on suspended 1D nanostructures. In this talk, we report an extension of atom-light coupling in a 2D nanophotonic device. Our system is based on silicon nitride microring resonators fabricated on a transparent membrane substrate, which is compatible with cold atom laser cooling. We present a simple and efficient optical guiding technique for trapping cold atoms in the near field of a planar nanophotonic structure with subwavelength precision, which leads to the observation of atom-photon coupling to a whispering-gallery mode in a microring resonator. We extract a cooperativity parameter of C~0.9 based on a microring with a moderate quality factor of Q=5x10⁴. We discuss our on-going effort for reaching higher-Q above 10⁶ and for trapping and further cooling a single to an array of guided atoms on a microring resonator that would promise a scalable on-chip cavity QED system with strong and cooperative atom-light coupling.