FIB-fabricated complex-shaped 3D chiral photonic silicon nanostructures

Area of Science:

• Materials Science
• Nanotechnology
• Optics

Background:

• Focused ion beam (FIB) fabrication is a key technology for creating complex silicon metasurfaces.
• FIB processing is known to introduce damage layers in silicon, increasing optical absorption losses.
• Silicon-on-sapphire (SOS) platforms offer unique properties for nanostructure fabrication.

Purpose of the Study:

• To investigate the structural and optical characteristics of FIB-fabricated silicon nanostructures on an SOS platform.
• To evaluate the effect of thermal oxidation on the optical properties of these nanostructures.
• To understand how oxidation influences the recovery of chiral optical features.

Main Methods:

• Fabrication of silicon subwavelength nanostructures using focused ion beam on a silicon-on-sapphire substrate.
• Characterization of nanostructure morphology and optical properties before and after thermal oxidation.
• Analysis of the impact of oxidation on optical absorption and chiral response.

Main Results:

• FIB fabrication creates nanostructures on the SOS platform with initial optical absorption losses.
• Thermal oxidation treatment leads to the recovery of chiral optical features in the FIB-patterned silicon nanostructures.
• The oxidation process significantly alters the optical behavior of the silicon nanostructures.

Conclusions:

• Thermal oxidation is an effective post-processing step to mitigate FIB-induced damage in silicon nanostructures.
• Oxidation enables the restoration of desirable chiral optical properties in fabricated silicon metasurfaces.
• This study highlights a method to improve the performance of FIB-fabricated nanophotonic devices.