Advanced Optical Programming of Individual Meta-Atoms Beyond the Effective Medium Approach

Area of Science:

• Photonics
• Materials Science
• Nanotechnology

Background:

• Active metasurfaces (MSs) with phase-change materials (PCMs) offer tunable optical functionalities.
• Current MSs typically switch the entire PCM, limiting programmability.
• Selective switching within individual meta-atoms is crucial for advanced MS applications.

Purpose of the Study:

• To demonstrate simultaneous control over the size, position, and crystallization depth of switched PCM within individual meta-atoms.
• To enable local modification of optical properties for amplitude and phase programming at the meta-atom scale.
• To move beyond effective medium response for enhanced metasurface capabilities.

Main Methods:

• Fabrication of a proof-of-principle MS using a PCM-covered aluminum-nanorod antenna array.
• Development of techniques for selective switching of PCM volume within each meta-atom.
• Characterization of locally modified optical properties.

Main Results:

• Demonstrated simultaneous control of switched PCM volume (size, position, depth) in individual meta-atoms.
• Achieved local programming of amplitude and light phase at the meta-atom scale.
• Showcased a method that surpasses traditional effective medium responses.

Conclusions:

• This work enables precise, localized control over optical properties in metasurfaces.
• The demonstrated technique allows for adaptive optical corrections and multi-functional programmable MSs.
• This approach opens new avenues for compact and reconfigurable photonic devices.