Single-double-band switchable optical circular polarizers based on surface plasmon resonance.

Area of Science:

• Optics and Photonics
• Plasmonics
• Nanotechnology

Background:

• Surface plasmon resonance (SPR) based filters offer tunable optical properties.
• Circular polarization filters are crucial for advanced communication and sensing.
• Existing filters often lack tunability or are complex to fabricate.

Purpose of the Study:

• To propose and investigate a novel bi-layer rod nanostructure for switchable single- and double-band circular polarization filtering.
• To explore the tunability of the filter's spectral response by adjusting geometric parameters.
• To elucidate the physical mechanisms governing the observed filtering effects.

Main Methods:

• Finite Element Method (FEM) simulations were employed to analyze the transmission spectra.
• The design involved a bi-layer nanorod structure.
• Parametric studies varied geometric parameters like layer distance, nanorod width, and length.

Main Results:

• The proposed structure achieved switchable single- and double-band circular polarization filtering.
• Filtering performance was highly dependent on nanorod length, with significant extinction ratios (up to 486 and 2020/129).
• Operating bandwidths reached 170 nm for single-band and 35 nm/70 nm for double-band operation.

Conclusions:

• The bi-layer nanostructure effectively demonstrates switchable circular polarization filtering.
• Geometric parameter control allows for tunable optical responses.
• The findings pave the way for integrated, low-cost optical devices in communication and sensing.