Sensitivity Enhancement by Etching Helical-Core Fibers Towards the Dispersion Turning Point

Helical-core fibers have been widely utilized for various applications such as orbital angular momentum manipulation, optical filtering, and sensing. In this work, we demonstrate the sensitivity enhancement of a helical-core fiber by tailoring the resonance wavelength towards the dispersion turning point (DTP) utilizing a post chemical etching process. The responses of the device on external parameters, including mechanical torsion, temperature, strain, and external refractive index, are investigated and compared. When the resonance is close to the DTP, the measured sensitivities with maximal magnitudes reach <tex-math notation="LaTeX">$-$</tex-math> 321.57 nm <tex-math notation="LaTeX">·</tex-math> mm/rad, 177.51 pm/ <tex-math notation="LaTeX">^∘</tex-math> C, <tex-math notation="LaTeX">$-$</tex-math> 1.27 pm/ <tex-math notation="LaTeX">μ</tex-math> , and 131.97 nm/refractive-index-unit for measuring the mechanical torsion, temperature, strain, and external refractive index respectively. The sensitivity magnitudes of torsion, temperature, and strain are enhanced by 7.93, 3.47, and 8.47 times respectively than that of the helical-core fiber without etching. Our work on the knowledge of modifying the resonance spectrum of the helical-core fibers provides an avenue for improving the sensing performance of optical devices.