Ring Resonator of Hollow-Core Photonic Crystal Fiber Based on Spatial Coupling Scheme

In this article, we proposed a hollow-core photonic crystal fiber (HCPCF) ring resonator based on a spatial coupling method, and the component is only 22 x 30 x 6 mm(3). When using a 7-core photonic crystal fiber with a mode field diameter of 10um, a ring resonator with the measured finesse of 18 can be built, indicating that the coupling loss is as low as 0.41 dB. Compact and low-loss closed resonator is accomplished using a highly integrated free space silicon optical bench manufactured by deep silicon etching and tiny optical lens package technology, which promotes the practicality of the HCPCF gyro. In addition, two important factors affecting the spatial optical coupling efficiency, the lens type and the fiber mode field size, are investigated in this article. The obtained results are instructive for all spatial optical coupling systems.