Novel fiber bottle microresonator add-drop filters

Abstract

Novel bottle microresonators fabricated from standard telecommunications optical fiber were recently shown to support helical whispering gallery modes (WGMs) extending along the bottle length between the bottle necks. Intensity maxima were observed around the turning points on both sides close to the bottle necks where the WGMs are effectively reflected. Selective excitation on one side of the bottle microresonator leads to strong power localization at a symmetrically located turning point for the WGMs and can potentially be exploited to form effective add-drop filters. Channel dropping characteristics have been studied experimentally for the first time in this novel type of microresonator. A tapered optical fiber (drawn down to 2-3 microns in diameter with effective index of approximately 1.2) was placed on one side of the bottle to excite the bottle WGMs. A similar tapered fiber placed symmetrically on the other side of the bottle acted as a probe to extract the excited modes. We have successfully extracted power from all the resonance wavelengths using the probe placed at appropriate positions along the bottle, leading to the potential to construct efficient all fiber add-drop filters.