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Fiber coupling to BaTiO3 glass microspheres in an aqueous environment
Oleksiy Svitelskiy1, Yangcheng Li, Arash Darafsheh
1Department of Physics and Optical Science, Center for Optoelectronics and Optical Communications, University of North Carolina at Charlotte, Charlotte, North Carolina 28223, USA.
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.
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