Non-adiabatic tapered fiber-based robust and efficient coupler for a WGM microresonator

Area of Science:

• Optics and Photonics
• Materials Science
• Micro-optics

Background:

• Whispering-gallery-mode (WGM) microresonators are sensitive optical devices.
• Efficiently coupling light into WGM microresonators is crucial for sensor applications.
• Conventional tapered fibers are often long and mechanically fragile.

Purpose of the Study:

• To propose and demonstrate a new, robust, and efficient coupling method for WGM microresonators.
• To develop a compact and cost-effective fiber coupler.
• To enhance the mechanical stability of WGM microresonator coupling.

Main Methods:

• Fabrication of an ultrashort (∼1 mm) non-adiabatic tapered fiber using arc discharge and flame heating.
• Characterization of the fiber's coupling efficiency and resonance excitation (Lorentzian and Fano).
• Testing the coupling method with various microresonator types (SNAP, bottle, sausage).

Main Results:

• Achieved coupling efficiencies up to 92%.
• Demonstrated improved mechanical robustness compared to conventional adiabatic fibers.
• Confirmed excitation of both Lorentzian and Fano resonances.
• Showcased high sensitivity to axial displacement.
• Validated the universality of the approach across different resonator geometries.

Conclusions:

• The proposed non-adiabatic tapered fiber offers a robust, efficient, and cost-effective solution for WGM microresonator coupling.
• This method is suitable for developing miniaturized, high-sensitivity, and multifunctional WGM optical sensors.
• The compact design and enhanced durability open new avenues for integrated photonic devices.