Nanofibers coated with Rare-Earth complexes.

Crystals and fibers doped with Rare Earth (RE) ions provide the basis to most of today's solid-state optical systems, from the laser and telecom industries, to emerging potential quantum applications such as quantum memories and optical to microwave conversion. The two platforms, doped crystals and doped fibers, seem nearly mutually exclusive, each having their own strengths and limitations; the former providing high homogeneity and coherence, and the latter offering the advantages of robust optical waveguides. Here we present a hybrid platform that does not rely on doping but rather on coating the waveguide - a silica nanofiber - with a monolayer of RE complexes. We describe the synthesis and assembly of the complexes' monolayer, as well as the characterization, and their application to tailor-fabricated nano-fibers. We present optical measurements with Yb-coated nanofibers at 300K, exhibiting fluorescence times of 0.9 ms similarly to doped inorganic crystals, and spectral linewidth of 6 nm. This scheme is general to all RE ions and oxygenated surfaces, which renders its feasibility to many applications of photonics, quantum optics and microwave.