We demonstrate the use of a near-field probe to map the angular dependence of high-and whispering-gallery modes in fused-silica microspheres. The mapping is performed by placing a micrometer-sized tip formed on the end of a monomode fiber into the evanescent field at the microsphere surface, causing Light to be coupled from the microsphere resonance into the fiber guided mode. The light output of the fiber is then measured while the tip is moved to different points on the microsphere surface. We have used this method to investigate the lifting of spherical degeneracy in the system.
Splitting of high-Q Mie modes induced by light backscattering in silica microspheres
D.S. Weiss,
Vahid Sandoghdar,
J. Hare,
V. Lefèvre-Seguin,
J.M. Raimond,
S. Haroche
We have observed that very high-and Mie resonances in silica microspheres are split into doublets. This splitting is attributed to internal backscattering that couples the two degenerate whispering-gallery modes propagating in opposite directions along the sphere equator. We have studied this doublet structure by high-resolution spectroscopy. Time-decay measurements have also been performed and show a beat note corresponding to the coupling rate between the clockwise and counterclockwise modes. A simple model of coupled oscillators describes our data well, and the backscattering efficiency that we measure is consistent with what is observed in optical fibers. (C) 1995 Optical Society of America
Eroded monomode optical fiber for whispering-gallery mode excitation in fused-silica microspheres
N. Dubreuil,
J.C. Knight,
D.K. Leventhal,
Vahid Sandoghdar,
J. Hare,
V. Lefèvre
We demonstrate the efficient excitation of high-Q whispering-gallery modes in near-spherical fused-silica microparticles in the size range 60-450 mu m by the use of an eroded monomode optical fiber. When the sphere is placed in the evanescent field of the guided fiber mode, light is resonantly coupled from the fiber into the microparticle. We report a broadening of resonance modes and a shift of the resonance central frequency as the coupling strength is increased by reduction of the gap between the sphere and the fiber.
Contact
Nano-Optics Division Prof. Vahid Sandoghdar
Max Planck Institute for the Science of Light Staudtstr. 2 91058 Erlangen, Germany
