Whispering gallery modes in prolate fibre microcavities

Summary form only given. Whispering gallery modes (WGMs) are resonances of circular dielectric cavities such as spheres, discs and cylinders. They can be efficiently excited by evanescent coupling from narrow tapered fibres, and their spectral properties in silica microspheres have been exploited to give add-drop filters and microlasers. We have also shown how they can be similarly excited in cylindrical fibres and used to measure diameter uniformity. We demonstrate a new type of silica microcavity with a prolate shape formed in an optical fibre using a carbon dioxide laser. Although relatively long they can be very narrow and have interesting WGM spectra. They could form the basis of new add-drop filters and microlasers that are easier to manipulate than microspheres.