Multi-curvities femtosecond laser aided microstructures for magnetic field sensing

Abstract

Magnetic sensors utilizing direct magneto-optic field coupling in an optical fiber Bragg grating (FBG) is proposed and demonstrated. The FBG's cladding is micro-machined into micro-curvities aided by femtosecond laser, and coated with TbDyFe, magnetic sensing element. Number of micro-curvities and laser energy under a laser beam were optimized during FBG micromachining and dramatically improved sensor performance. Six-micro-groove sensor is four times more sensitive as compared to non-micro-grooved standard FBG sample. The effect of 18 mW laser pulse power impacted magnetic sensitivity of magnitude 0.6 pm/mT as compared to 0.14 pm/mT on non-microstructured standard FBG sensor. The depth of the deposited magnetostrictive film was measured as ~5 µm.