title: Refractive index sensitivity characteristics near the dispersion turning point of the multimode microfiber-based Mach-Zehnder interferometer.
abstract: The turning point of the refractive index (RI) sensitivity based on the multimode microfiber (MMMF) in-line Mach-Zehnder interferometer (MZI) is observed. By tracking the resonant wavelength shift of the MZI generated between the HE(11) and HE(12) modes in the MMMF, the surrounding RI (SRI) could be detected. Theoretical analysis demonstrates that the RI sensitivity will reach ±∞ on either side of the turning point due to the group effective RI difference (G) approaching zero. Significantly, the positive sensitivity exists in a very wide fiber diameter range, while the negative sensitivity can be achieved in a narrow diameter range of only 0.3 μm. Meanwhile, the experimental sensitivities and variation trend at different diameters exhibit high consistency with the theoretical results. High RI sensitivity of 10777.8 nm/RIU (RI unit) at the fiber diameter of 4.6 μm and the RI around 1.3334 is realized. The discovery of the sensitivity turning points has great significance on trace detection due to the possibility of ultrahigh RI sensitivity.
authors.forename: Haipeng
authors.initials: H
authors.lastname: Luo
authors.forename: Qizhen
authors.initials: Q
authors.lastname: Sun
authors.forename: Xiaolei
authors.initials: X
authors.lastname: Li
authors.forename: Zhijun
authors.initials: Z
authors.lastname: Yan
authors.forename: Yanpeng
authors.initials: Y
authors.lastname: Li
authors.forename: Deming
authors.initials: D
authors.lastname: Liu
authors.forename: Lin
authors.initials: L
authors.lastname: Zhang
mesh_terms: D003198:Computer Simulation; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005336:Fiber Optic Technology / Q000295:instrumentation*; D007368:Interferometry / Q000295:instrumentation*; D008027:Light; D008904:Miniaturization; D008962:Models, Theoretical; D012031:Refractometry / Q000295:instrumentation*; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity