Improvement on refractive index sensing by exploiting the tapered two-mode fibers

Fang Fang, Bing Sun, Zuxing Zhang, Jing Xu, Lin Zhang

Research output: Contribution to journalArticlepeer-review


The spectral characteristics and sensitivities of a tapered two-mode fiber sandwiched between two single-mode fibers are systematically investigated. Theoretical calculations reveal that a dispersion turning point (DTP) appears when the group effective refractive index (RI) difference between the fundamental mode and the higher-order mode equals zero; as a result, ultrahigh RI sensitivities can be achieved. Furthermore, the location of the DTP is strongly dependent on the tapering condition. Then, we experimentally demonstrate high sensitivities of the RI sensor with the waist diameter of ~4 μm by means of immersing it in a flow cell filled with glycerol solution. In further tracking of the resonant wavelength shift around the DTP, it is found that the proposed RI sensor exhibits a sensitivity of 1.81 × 104 nm/RIU and a limit of detection down up to 3.29 × 10 5 RIU in a liquid glycerol solution.
Original languageEnglish
Article number110604
JournalChinese Optics Letters
Issue number11
Early online date12 Sept 2019
Publication statusPublished - 1 Nov 2019

Bibliographical note

Funding: National Natural Science Foundation of China (No. 61505119), the National Postdoctoral Program for Innovative Talents (No. BX201600077), the Brain Gain Foundation of Nanjing University of Posts and Telecommunications (No. NY215040), the China Postdoctoral Science Foundation (No. 2017M611877), and the Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province (No. GD201706).


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