| Popis: |
The particular properties of hollow whispering gallery resonators should lead to the advancement of bio- and chemical sensing applications. In this talk, we report on the fabrication of, and mode propagation in, hollow, thin-walled microcavities, known as microbubbles or microbottles, which are made from microcapillaries that are pretapered, then heated using a CO2 laser while flowing air through them. The resulting cavity consists of a thin glass shell supported on a hollow stem through which fluid can flow. Whispering gallery modes supported in the wall of the cavity create an evanescent field extending from both the inner and outer surfaces. For higher order modes, and playing with material refractive indices, the system can be engineered so that most of the optical energy extends into the contained fluid, thereby allowing for strong interactions to be present; such a cavity is called a quasi-droplet. Even tiny changes to the fluid, such as the presence of nanoparticles, can lead to a significant shift of the resonance frequencies of the whispering gallery modes. These strongly interacting quasi-droplets make hollow microresonators uniquely suited for sensing applications. |
