Optical racetrack ring-resonator based on two U-bent microfibers

We experimentally demonstrate an optical racetrack ring-resonator with four optical ports constructed using two U-shaped bent microfibers placed into direct physical contact. Localized light is clearly observed along the closed loop path as a result of the resulting strong optical resonance. The resonator was embedded in a low-index polymer matrix to improve the long term mechanical and optical stability allowing a detailed study of its polarization characteristics