title: Fiber refractive index sensor based on dual polarized Mach-Zehnder interference caused by a single-mode fiber loop.
abstract: A novel refractive index (RI) sensor head is proposed and experimentally demonstrated in this paper. The proposed sensor head is composed of a segment of bared single-mode fiber and a fiber holder that is fabricated by a 3D printer. The mechanism of the sensor head is based on dual polarized Mach-Zehnder interference. According to the aforementioned mechanism, we derived that the RI responses of the resonance dips possess an exponential functional manner when the E field is along the fast or slow axes. In addition, based on the finite element method, we found that the resonance dips wavelength responses are more sensitive when the input E field is along the fast axis. A confirmation experiment was performed, and the results confirmed our hypothesis. The maximum arithmetic mean value of RI response is about 657.895  nm/RIU for the proposed sensor head when the ambient RI changes from 1.3350 to 1.4110. Moreover, in the case of the proposed liquid RI sensor head, aligning the E field along the fast axis is the potentially needed condition for polarization.
authors.forename: Lei
authors.initials: L
authors.lastname: Chen
authors.forename: Wei-Gang
authors.initials: WG
authors.lastname: Zhang
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.forename: Quan
authors.initials: Q
authors.lastname: Zhou
authors.forename: Jonathan
authors.initials: J
authors.lastname: Sieg
authors.forename: De-Long
authors.initials: DL
authors.lastname: Zhao
authors.forename: Biao
authors.initials: B
authors.lastname: Wang
authors.forename: Tie-Yi
authors.initials: TY
authors.lastname: Yan
authors.forename: Song
authors.initials: S
authors.lastname: Wang
mesh_terms: D004560:Electricity; D005336:Fiber Optic Technology / Q000379:methods*; D007368:Interferometry / Q000379:methods*; D055100:Optical Fibers; D012031:Refractometry