Freestanding metasurfaces for optical frequencies.

Area of Science:

• Optics and Photonics
• Materials Science
• Nanotechnology

Background:

• Metasurfaces offer precise control over light properties.
• Existing metasurfaces often require bulky substrates.
• Need for ultrathin, freestanding optical components.

Purpose of the Study:

• To develop freestanding metasurfaces with optical frequencies.
• To demonstrate the fabrication and functionality of ultrathin metasurfaces.
• To showcase applications in beam shaping and focusing.

Main Methods:

• Fabrication via focused ion beam milling of nanovoids in a carbon film.
• Deposition of gold via thermal evaporation.
• Removal of carbon film using plasma ashing.

Main Results:

• Achieved freestanding metasurfaces with a total thickness of 40 nm.
• Demonstrated a metasurface lens with a 1 mm focal length using V-shaped nanovoids.
• Created a metasurface phase plate transforming Gaussian beams into Laguerre-Gaussian modes using rectangular nanovoids.

Conclusions:

• Ultrathin, freestanding optical metasurfaces are feasible.
• The demonstrated fabrication method allows for versatile nanovoid designs.
• These metasurfaces are promising for advanced optical applications requiring miniaturization.