Highly efficient optical power transfer to whispering-gallery modes by use of a symmetrical dual-coupling configuration

We report that greater than 99.8% optical power transfer to whispering-gallery modes was achieved in fused-silica microspheres by use of a dual-tapered-fiber coupling method. The intrinsic cavity loss and the taper-to-sphere coupling coefficient are inferred from the experimental data. It is shown that the low intrinsic loss and the symmetrical dual-coupling structure are crucial for obtaining the high coupling efficiency. (C) 2000 Optical Society of America OCIS codes: 230.5750, 230.3990, 060.1810, 230.1150.