Microfiber magnetic field sensor with enhanced sensitivity and resolution

Abstract

Magnetic field as a kind of objective substance contains abundant physical information, so high sensitivity and resolution measurement for the magnetic field has great significance in scientific and industrial fields. In this work, we verify a highly sensitive cascaded Mach-Zehnder interferometer (C-MZI) sensor based on optical Vernier effect for the magnetic field measurement, which is composed of a reference MZI (R-MZI) without magnetic fluids (MFs) connected in series with a sensing MZI (S-MZI) with MFs. An evident envelope and shift induced by the external magnetic field is observed in the transmission spectra of the C-MZI, resulting in the sensitivity being elevated by an amplification factor. The experimental results reveal a wavelength sensitivity of -5.148 nm/mT in the range of 10.15~30.44 mT, being ~4.77 of that in the single S-MZI. In order to further improve the detection resolution of the magnetic field, a magnetic field measurement system based on the combination of the above S-MZI and an optoelectronic oscillator (OEO) is proposed, and the spectral response is tested in a small magnetic field range of 1.45~1.90 mT, obtaining a spectral sensitivity of 3.18 kHz/mT, which proves the detection of less than 1 Oe. The designed sensor and system possess the merits of high sensitivity, high resolution, simple fabrication, fast response and low phase noise, having broad prospects in the fields of magnetic field measurement.