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Sensors (Basel). 2017 Jul 7;17(7). pii: E1590. doi: 10.3390/s17071590.

Ultrasensitive Magnetic Field Sensing Based on Refractive-Index-Matched Coupling.

Rao J1, Pu S2,3, Yao T4, Su D5.

Author information

1
College of Science, University of Shanghai for Science and Technology, Shanghai 200093, China. 152251908@st.usst.edu.cn.
2
College of Science, University of Shanghai for Science and Technology, Shanghai 200093, China. shlpu@usst.edu.cn.
3
Shanghai Key Laboratory of Modern Optical System, University of Shanghai for Science and Technology, Shanghai 200093, China. shlpu@usst.edu.cn.
4
College of Science, University of Shanghai for Science and Technology, Shanghai 200093, China. 162281924@st.usst.edu.cn.
5
College of Science, University of Shanghai for Science and Technology, Shanghai 200093, China. 142231886@st.usst.edu.cn.

Abstract

An ultrasensitive magnetic field sensor is proposed and investigated experimentally. The no-core fiber is fusion-spliced between two pieces of single-mode fibers and then immersed in magnetic fluid with an appropriate value of refractive index. Under the refractive-index-matched coupling condition, the guided mode becomes leaky and a coupling wavelength dip in the transmission spectrum of the structure is observed. The coupling wavelength dip is extremely sensitive to the ambient environment. The excellent sensitivity to the refractive index is measured to be 116.681 μm/RIU (refractive index unit) in the refractive index range of 1.45691-1.45926. For the as-fabricated sensors, the highest magnetic field sensing sensitivities of 6.33 and 1.83 nm/mT are achieved at low and high fields, respectively. The sensitivity is considerably enhanced compared with those of previously designed, similar structures.

KEYWORDS:

magnetic field sensor; magnetic fluid; refractive-index-matched coupling; singlemode-no-core-singlemode fiber structures

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