Generating far-field orbital angular momenta from near-field optical chirality.

Area of Science:

• Optics and Photonics
• Materials Science
• Nanotechnology

Background:

• Orbital angular momentum (OAM) is a fundamental property of light.
• Chiral plasmonic nanostructures offer unique light-matter interactions.
• Controlling OAM transfer is crucial for advanced optical applications.

Purpose of the Study:

• To demonstrate OAM transfer using chiral plasmonic nanostructures.
• To investigate the role of nanostructure design in tailoring vortex beams.
• To elucidate the influence of a central aperture on OAM selection rules.

Main Methods:

• Design and fabrication of chiral plasmonic nanostructures on both sides of a metallic membrane.
• Utilizing a central aperture to connect the nanostructure layers.
• Experimental characterization of far-field vortex beams and OAM indices.

Main Results:

• Successful demonstration of OAM transfer through the chiral nanostructures.
• Tunable OAM indices of far-field vortex beams achieved via nanostructure design.
• OAM selection rules derived from the central aperture show excellent agreement with experimental data.

Conclusions:

• Chiral plasmonic nanostructures on a membrane are effective for OAM transfer.
• Nanostructure design provides control over vortex beam properties.
• The central aperture plays a critical role in defining OAM selection rules.