Strong optical activity from twisted-cross photonic metamaterials.

Area of Science:

• Photonics
• Metamaterials Science
• Nanotechnology

Background:

• Recent theoretical work and microwave experiments suggested the possibility of novel optical properties in specific metamaterial structures.
• Coupled plasmonic systems offer tunable optical responses based on their geometry and constituent materials.

Purpose of the Study:

• To fabricate and characterize photonic metamaterials based on pairs of twisted gold crosses.
• To investigate the optical properties, specifically circular dichroism and optical activity, of these metamaterials in the near-infrared regime.
• To compare experimental results with theoretical predictions.

Main Methods:

• Fabrication using two successive electron-beam-lithography steps.
• Intermediate planarization utilizing a spin-on dielectric.
• Optical characterization including measurement of transmittance spectra and polarization properties.

Main Results:

• Successful fabrication of photonic metamaterials composed of twisted gold crosses.
• Observation of two effective resonances in the 1-2 micrometer wavelength range.
• Demonstration of pronounced circular dichroism and a broad spectral regime with strong optical activity (pure linear polarization rotation).
• Experimental optical transmittance spectra show good agreement with theoretical models.

Conclusions:

• The fabricated twisted gold cross metamaterials exhibit unique optical properties, including significant circular dichroism and optical activity.
• The results validate theoretical predictions for such coupled plasmonic systems.
• These metamaterials show potential for applications requiring precise control over light polarization in the near-infrared spectrum.