Alignment-Free Coupling in Whispering Gallery Mode Resonator Based on a Tapered Capillary

A whispering gallery mode microsphere resonator based on a capillary is presented, which consists of a tapered capillary with thick wall and an inserted microsphere, fusion spliced using conical fusing mode with single mode fiber at both of its ends. The device is featured with alignment-free coupling of light traveling in the capillary wall into the microsphere, high robustness due to the thick capillary wall, simple in fabrication, low in cost and good operation stability, which make it exhibit broad application prospects in the field of photonics.