Magnetic Field Sensor Based on Photonic Crystal Fiber Taper Coated With Ferrofluid

Abstract

A novel and compact magnetic field sensor based on a tapered photonic crystal fiber (PCF) coated with ferrofluid is proposed. It consists of a section of tapered PCF, which is spliced between two single-mode fibers with a waist diameter of $24~\mu $ m. The ferrofluid is filled in the capillary to coat the PCF taper. Experimentally, the refractive index (RI) of the ferrofluid increased under increasing magnetic field intensity ( ${H}$ ) with a sensitivity of $\mathbf {4 \times 10}^{\mathbf {-5}}$ RIU/Gs and the RI sensitivity in the evanescent field is 401 nm/RIU. Therefore, the interference spectrum is shifted as the change of $\boldsymbol {H}$ ranged from 100 to 600 Gs with a sensitivity of 16.04 pm/Gs and resolution of 0.62 Gs. The proposed magnetic field sensor is attractive due to its compact size, low cost, and immunity to electromagnetic interference beyond what conventional magnetic field sensors can offer.