Advanced Plasmonic Fiber-Optic Sensor for High Sensitivity Measurement of Magnetic Field

An advanced plasmonic sensor for high sensitivity measurement of magnetic field is presented. It is based on the combination of a SPR refractometer (doubly-deposited tapered optical fiber) with magnetic fluids used as transducers. The device is compact and robust and has been theoretically analyzed and completely characterized, showing a very good experimental performance. We have studied the dependence of the response of the device with the direction of the field, confirming that, as expected, the sense of the variation of the refractive index is opposite for parallel and perpendicular fields, which is an interesting feature for practical applications. We have also evaluated the dependence on the concentration of the employed magnetic fluid and the influence of the chosen type of ferrofluid. In all these measurements the sensitivity experimentally obtained is amongst the highest reported in the literature for this kind of devices and we have extended the dynamic range. Finally, we have applied a novel, auto-referential, signal processing algorithm to the measurements, showing its possibilities. The obtained experimental results demonstrate the feasibility and the advantages of the application of SPR fiber-optic sensors to magnetic field measurements.