Fusion-spliced microbubble resonators filled with F₃O₄ nanoparticles achieve axial strain sensitivity enhancement

In this paper, we propose an axial strain sensitivity enhancement method based on what we believe to be a novel fusion-spliced microbubble resonator filled with F₃O₄ nanoparticles. The fusion-spliced microbubble resonator is formed by splicing a hollow-core bubble and a single-mode fiber at both ends. The temperature inside the resonator is elevated by passing control light into one end of the resonator. The temperature increase can change the material properties of the silicon oxide resonator to increase the strain sensitivity. The effect of temperature on the strain sensitivity of the resonator was investigated theoretically and experimentally. A maximum sensitivity of 16.4 pm/µε was measured by adjusting the control light, and the strain sensitivity increase was achieved without realizing ultra-thin wall thickness. This novel microbubble resonator structure is expected to be used in applications such as high-precision sensing or tunable lasers.