Micro-Deformed Looped Fiber Taper With High Sensitivity to Refractive Index

We report a highly sensitive refractive index sensor based on a looped micro-deformed tapered fiber. The microdeformation is induced by first shaping the taper into a loop, and then, a ball-shaped fiber end bends the taper waist. While the tapered fiber loop is bent, a heat pulse from a CO2-laser is applied for 2 seconds, just enough to avoid the fusion with the balled fiber end. In this way, a sm...