Ultra-high-Q tunable whispering-gallery-mode microresonator

The paper here presents a fully tunable ultra-high-Q-whispering-gallery-mode "bottle microresonator", fabricated from standard optical glass fibres. Due to its highly prolate shape, the bottle microresonator gives rise to a class of whispering-gallery-modes (WGMs) with advantageous properties. In addition to the radial confinement by continuous total internal reflection at the resonator surface, the light in these "bottle modes" oscillates back and forth along the resonator axis between two turning-points which are defined by an angular momentum barrier. The resulting axial standing wave structure can be compared to the one observed in Fabry-Perot microresonators.