title: Fiber coupling to BaTiO3 glass microspheres in an aqueous environment.
abstract: Compact microspheres with high-quality (Q) whispering gallery modes are required for many applications involving liquid immersion, such as sensing nanoparticles and studying resonant radiative pressure effects. We show that high-index (1.9 and 2.1) barium titanate glass (BTG) microspheres are perfect candidates for these applications due to their high-Q (∼10(4) in the 1100-1600 nm range) resonances evanescently excited in spheres with diameters of 4-15 μm. By reattaching the spheres at different positions along a tapered optical fiber, we show that the coupling constant exponentially increases with thinner fiber diameters. We demonstrate the close to critical coupling regime with intrinsic Q=3×10(4) for water immersed 14 μm BTG spheres.
authors.affiliation: Department of Physics and Optical Science, Center for Optoelectronics and Optical Communications, University of North Carolina at Charlotte, Charlotte, North Carolina 28223, USA.
authors.forename: Oleksiy
authors.initials: O
authors.lastname: Svitelskiy
authors.forename: Yangcheng
authors.initials: Y
authors.lastname: Li
authors.forename: Arash
authors.initials: A
authors.lastname: Darafsheh
authors.forename: Misha
authors.initials: M
authors.lastname: Sumetsky
authors.forename: David
authors.initials: D
authors.lastname: Carnegie
authors.forename: Edik
authors.initials: E
authors.lastname: Rafailov
authors.forename: Vasily N
authors.initials: VN
authors.lastname: Astratov