Cladding modes fiber coupling to silica micro-resonators based on long period gratings

A novel method based on long period fiber gratings (LPGs) for coupling light to high-Q silica whispering gallery mode (WGM) resonators is presented. An LPG couples the fundamental mode of a fiber to higher order LP cladding modes at selected frequencies. At an adiabatically tapered section of the fiber following the LPG we demonstrated effective coupling of these cladding modes to WGMs both in silica microspheres and microbubbles. The taper is about one order of magnitude thicker than standard tapers used for the same purpose. Therefore this new method offers improved robustness for practical applications.