title: Fiber ring resonator with a nanofiber section for chiral cavity quantum electrodynamics and multimode strong coupling.
abstract: We experimentally realize an optical fiber ring resonator that includes a tapered section with a subwavelength-diameter waist. In this section, the guided light exhibits a significant evanescent field which allows for efficient interfacing with optical emitters. A commercial tunable fiber beam splitter provides simple and robust coupling to the resonator. Key parameters of the resonator such as the out-coupling rate, free spectral range, and birefringence can be adjusted. Thanks to the low taper- and coupling-losses, the resonator exhibits an unloaded finesse of F=75±1, sufficient for reaching the regime of strong coupling for emitters placed in the evanescent field. The system is ideally suited for trapping ensembles of laser-cooled atoms along the nanofiber section. Based on measured parameters, we estimate that the system can serve as a platform for optical multimode strong coupling experiments. Finally, we discuss the possibilities of using the resonator for applications based on chiral quantum optics.
authors.forename: Philipp
authors.initials: P
authors.lastname: Schneeweiss
authors.forename: Sophie
authors.initials: S
authors.lastname: Zeiger
authors.forename: Thomas
authors.initials: T
authors.lastname: Hoinkes
authors.forename: Arno
authors.initials: A
authors.lastname: Rauschenbeutel
authors.forename: Jürgen
authors.initials: J
authors.lastname: Volz