1209.2475 (Masazumi Fujiwara et al.)

Coupling of ultrathin tapered fibers with high-Q microsphere resonators
at cryogenic temperatures and observation of phase-shift transition from
undercoupling to overcoupling    [PDF]

Masazumi Fujiwara, Tetsuya Noda, Akira Tanaka, Kiyota Toubaru, Hong-Quan Zhao, Shigeki Takeuchi

We cooled ultrathin tapered fibers to cryogenic temperatures and controllably coupled them with high-Q microsphere resonators at a wavelength close to the optical transition of diamond nitrogen vacancy centers. The 310-nm-diameter tapered fibers were stably nanopositioned close to the microspheres with a positioning stability of approximately 10 nm over a temperature range of 7-28 K. A cavity-induced phase shift was observed in this temperature range, demonstrating a discrete transition from undercoupling to overcoupling.

View original: http://arxiv.org/abs/1209.2475