Enhancing the radiation efficiency of dye doped microresonators using coupling effects with a suspended core microstructured optical fiber

Abstract

Recently we demonstrated that a dye-doped microresonator positioned onto the tip of a suspended core Microstructured Optical Fiber can be used as a dip sensor. In this architecture, the resonator is located on an air hole next to the fiber core, enabling a significant portion of the sphere to overlap with the guided light emerging from the fiber tip. When the resonator is excited through the suspended core fiber it exhibits an unusually high radiative efficiency, which was initially attributed to the higher excitation efficiency enabled by this architecture. Here we demonstrate that it is possible to enhance the radiative emission of a microresonator attached to the suspended core fiber tip by changing the size of the resonator and how it is positioned on the fiber tip. In particular, we have found that the way in which the sphere interacts with the air hole cavity of the suspended core fiber significantly changes its emission characteristics. We found that the enhancement was dependent upon the interaction between the modes of the resonator with the confined geometry of the suspended core fiber rather than a higher excitation efficiency alone. We also evaluate the impact of the radiative enhancement on the WGM lasing threshold in different configurations.