Optical microfiber resonator: principle and applications

Microfibers tapered from conventional optical fibers with diameters ranging from hundreds of nanometers to several micrometers possess various advantages including large evanescent field, strong light confinement, high optical nonlinearity, flexible configurability, and low-loss connection to other fiberized systems, which makes it an open platform for miniaturization and integration of all-fiber devices. As a fundamental opto-electronic component, optical resonators have got comprehensively researched and widely applied in the fields of optical communication, sensing, signal processing, and quantum photonics. Traditional optical resonators are fabricated through lithography which is relatively complicated. With the maturation of microfiber fabrication methods, optical resonator based on optical microfibers was demonstrated and developed. As an optical coupling device based on evanescent field coupling, the microfiber resonator features in low insertion loss, high finesse, easy fabrication, and compatibility with fiber systems. It can be utilized in domains of filter, sensor, modulator, and fiber laser. In this article, we summarize the recent progress in the microfiber resonators research fields, covering fundamental characteristics, fabrication methods, and applications of microfiber resonators.