Annular nanoantenna on fibre micro-axicon

Area of Science:

• Optics and Photonics
• Nanotechnology
• Electromagnetism

Background:

• Traditional loop antennas are crucial in radio frequency applications for detecting electromagnetic fields.
• Extending antenna principles to the optical domain presents challenges due to scale and material properties.
• Developing nanoscale optical sensors requires precise engineering of light-matter interactions.

Purpose of the Study:

• To propose and validate the concept of optical nano-antennas based on loop antenna principles.
• To design nanocollectors sensitive to specific vectorial electric and magnetic field components.
• To investigate the electromagnetic response of nanostructured materials at optical frequencies.

Main Methods:

• Micromachining a one-micron-diameter gold nanoring on a cone lens apex from a tapered optical fiber.
• Utilizing Bessel beams with radial and azimuthal polarization to probe the nano-antenna.
• Characterizing the detection capabilities for longitudinal electric and magnetic field components.

Main Results:

• Demonstrated that the gold nanoring functions as a nano-antenna.
• Successfully detected the longitudinal electric field component from a radially polarized Bessel beam.
• Observed detection of the longitudinal magnetic component from an azimuthally polarized Bessel beam.
• The annular nano-antenna exhibited optical inductance properties in the magnetic field detection case.

Conclusions:

• The proposed optical nano-antenna design is effective for detecting specific field components.
• This work extends antenna theory into the optical regime, enabling new sensing modalities.
• The findings pave the way for a new generation of highly sensitive optical nanocollectors.