Packaged optofluidic microbottle resonator for high-sensitivity bidirectional magnetic field sensing

Area of Science:

• Photonics
• Sensor Technology
• Materials Science

Background:

• Optofluidic resonators offer unique sensing capabilities.
• Magnetic fluids exhibit tunable optical properties under magnetic fields.
• Accurate bidirectional magnetic field sensing is crucial for various applications.

Purpose of the Study:

• To demonstrate a high-sensitivity bidirectional magnetic field sensor.
• To analyze the influence of resonator parameters on sensor performance.
• To investigate the response of the sensor to magnetic fields applied in different directions.

Main Methods:

• Fabrication of a thin-wall optofluidic microbottle resonator (OFMBR) via capillary etching.
• Packaging of the OFMBR with a tapered fiber for robust optical coupling.
• Theoretical analysis of OFMBR sensitivity concerning wall thickness and radial modes.
• Experimental measurement of magnetic field sensitivity with perpendicular and parallel field orientations.

Main Results:

• Achieved a magnetic field sensitivity of 98.23 pm/mT with the second-order radial mode for perpendicular fields.
• Obtained a sensitivity of -304.80 pm/mT with the third-order radial mode for parallel fields.
• Demonstrated a low detection limit of 0.0656 mT for parallel field detection.
• Observed opposite refractive index responses (redshift/blueshift) of the magnetic fluid with varying magnetic field intensities.

Conclusions:

• The developed sensor exhibits high sensitivity, reliability, and ease of fabrication.
• The OFMBR-based sensor shows significant potential for bidirectional magnetic field measurements.
• The bidirectional sensing capability is achieved by exploiting the distinct responses of magnetic fluid to different magnetic field orientations.