Magnetic Field Tunability of Square Tapered No-Core Fibers Based on Magnetic Fluid

A magnetic-field-tuned photonics device based on magnetic fluid (MF) and a square tapered no-core fiber (NCF) sandwiched between two single-mode fibers (SMFs) has been demonstrated experimentally and theoretically. The enhanced evanescent field effect in the NCF is achieved by tapering the square NCF utilizing a fusion splicer. The spectral dependence of the proposed device on the applied magnetic-field intensity has been investigated. The results indicate that the multimode interference spectrum exhibits a blue-shift with the increment of the magnetic-field intensity. A maximal sensitivity of -18.7 pm/Oe is obtained for a magnetic field strength ranging from 25 to 450 Oe. The proposed tunable device has several advantages, including low cost, ease of fabrication, simple and compact structure, and high sensitivity. Therefore, the magnetic-field-tuned square tapered NCF is expected to find potential applications in the fields of optical fiber sensors, as well as fiber communications.