Magnetic field optical sensor based on Lossy Mode Resonances

We present a magnetic field optical fiber sensor. The configuration chosen for this purpose is a tapered single mode optical fiber coated with a thin film of a magneto-optic alloy, which is made of cobalt and nickel. The coating has been fabricated by means of sputtering. This alloy was used to build the nano-coating which produces the Lossy Mode Resonance (LMR) and that is sensitive to magnetic fields. Then, the device was placed in the air gap of an electrical transformer for applying magnetic field. Wavelength shifts of 2 nm have been achieved for 330 mT of magnetic field. This is the first time, for the best of our knowledge, that LMRs have been used for magnetic field sensing.