Effects of end surface and angle coupling on mode splitting and suppression in a cylindrical microcavity

A cylindrical microcavity conventionally has the characteristics of simple fabrication and high Q factor, where the rich physics of mode splitting and suppression caused by mode excitation, coupling, and interference have been realized for highly sensitive sensing and cavity quantum electrodynamics. In this paper, we show experimentally and theoretically a simple method to tailor these two mechanisms via near-end surface and angle coupling in a single-mode fiber cylindrical microcavity. Mode splitting can be enhanced due to the interference between localized and axial modes as the effect of near-end surface coupling, validated by the coupled-mode model. Besides, we also demonstrate that the coupling angle between the fiber taper and cylindrical microcavity can efficiently affect the mode suppression in the transmission spectrum. Such a device has a simple structure, simple fabrication process, and simple mechanism to tailor the mode splitting and suppression for applications in cavity quantum electrodynamics, sensitive sensing, and other topics of photonics.