A Micron-Range Displacement Sensor Based on Thermo-Optically Tuned Whispering Gallery Modes in a Microcapillary...

Area of Science:

• Photonics
• Nanotechnology
• Materials Science

Background:

• Whispering-gallery mode (WGM) resonators offer high sensitivity for sensing applications.
• Liquid crystals (LCs) exhibit significant thermo-optic effects useful for optical sensing.
• Magnetic nanoparticles (MNPs) can be used for localized heating in microdevices.

Purpose of the Study:

• To propose and experimentally demonstrate a novel micron-range displacement sensor.
• To utilize the thermo-optic effect in a liquid crystal-filled microcapillary resonator.
• To integrate magnetic nanoparticles for localized thermal control.

Main Methods:

• Fabrication of a microcapillary resonator filled with nematic liquid crystal.
• Coating a fiber half-taper tip with magnetic nanoparticles.
• Utilizing a pump laser to induce thermo-optic effects via MNPs.
• Monitoring spectral shifts of WGM resonances in response to displacement.

Main Results:

• Experimental demonstration of a micron-range displacement sensor.
• Achieved sensitivity of 15.44 pm/µm.
• Demonstrated response time of 260 ms with good reversibility and repeatability.
• Simulations showed good agreement with experimental WGM spectral shifts.

Conclusions:

• The proposed sensor effectively measures micron-range displacements.
• The device leverages the thermo-optic properties of liquid crystals and localized heating by magnetic nanoparticles.
• Potential applications include micro-manufacturing, precision measurement, and medical instruments.