Ultrasensitive magnetic field sensor based on cladding-etched long-period grating.

Area of Science:

• Photonics and optical sensing
• Magneto-optics
• Fiber optic technology

Background:

• Fiber-optic sensors offer remote and non-invasive measurement capabilities.
• Magnetic field sensing is crucial for various applications, including electrical systems and scientific research.
• Long-period fiber gratings (LPFGs) are versatile optical components for sensing applications.

Purpose of the Study:

• To demonstrate a novel fiber-optic magnetic field sensor with enhanced sensitivity.
• To investigate the performance of a cladding-etched LPFG integrated with magnetic fluid near its dispersion turning point (DTP).
• To achieve ultrahigh sensitivity for detecting weak magnetic fields.

Main Methods:

• Fabrication of a cladding-etched LPFG with reduced cladding diameter.
• Integration of the etched LPFG with a magnetic fluid (MF).
• Characterization of the sensor's response to varying magnetic field intensities near the DTP, leveraging high surrounding refractive index sensitivity and magneto-optical properties of MF.

Main Results:

• The proposed sensor achieved a high magnetic field intensity sensitivity of 44.69 nm/mT within the 3-7.4 mT range.
• A minimum detectable magnetic field intensity of 0.45 µT was achieved, limited by the optical spectrum analyzer's resolution.
• The fundamental mode coupling to the LP_0,2 cladding mode near the DTP significantly enhanced sensitivity.

Conclusions:

• The developed etched DTP-LPFG-based sensor exhibits ultrahigh sensitivity for magnetic field detection.
• The sensor's performance is attributed to the synergistic effects of the etched LPFG structure and the magnetic fluid.
• Potential applications in magnetic field monitoring and electrical systems are highlighted.