Femtosecond laser ablation of microstructures in fiber and application in magnetic field sensing

Abstract

A novel (to our knowledge) 3D microstructure manufactured by a femtosecond laser in fiber Bragg grating (FBG) fiber cladding is proposed. The special spiral parameters including single thread and double thread with certain pitches of 60 and 80 μm are controlled by the feed and rotation speed of a rotary fixture. Moreover, supermagnetostrictive TbDyFe film with a thickness of nearly 6 μm is deposited on microgrooves of a FBG by magnetron sputtering technology to form the magnetic field sensing probe. Experimental results demonstrate that a FBG with a double-thread microstructure has a sensitivity of 1.1 pm/mT responding to a magnetic field, and in a theoretical situation, it is approximately six times higher than the original optical fiber grating (approximately 0.2 pm/mT). This new microstructure and method show great prospect in the magnetic field sensing domain.