Balloon-shaped fiber surface nanoscale axial photonic microresonator for micro-displacement measurement.

In this Letter, we demonstrate a micro-displacement sensor based on a balloon-shaped fiber surface nanoscale axial photonic (SNAP) microresonator. The SNAP microresonator is fabricated by fiber bending to introduce nanoscale effective radius variations (ERVs) on the fiber surface. Displacement measurement based on the balloon-shaped SNAP microresonator is realized based on the ERV modulation resulting from the change in the bending radius of the balloon-shaped structure. An advantage of this approach is that the displacement measurement range is not limited to the axial length of the SNAP region. The experimental results show that the displacement measurement range of the balloon-shaped fiber SNAP microresonator can reach 2500 µm and that the minimum measurement resolution is 0.1 µm. This large-range, high-resolution, and low-cost micro-displacement sensor has the potential to be a promising candidate in high-precision displacement measurement applications.