Broadband circular polarizer based on twisted plasmonic nano-disks

Area of Science:

• Plasmonics and Nanophotonics
• Optical Engineering
• Materials Science

Background:

• Broadband circular polarizers are crucial optical components with applications in displays, imaging, and telecommunications.
• Surface plasmon resonance in metal nanostructures offers a tunable platform for designing efficient polarizers.
• Existing designs often face limitations in bandwidth, extinction ratio, or fabrication complexity.

Purpose of the Study:

• To design and simulate a novel broadband circular polarizer using a twisted multilayer double semi-disc nanostructure.
• To investigate the performance of the proposed structure in terms of extinction ratio and bandwidth.
• To explore the influence of geometric parameters on the polarizer's performance and understand the underlying plasmonic mechanisms.

Main Methods:

• Finite element method (FEM) simulations were employed to analyze the transmission spectra of the designed nanostructure.
• Simulations were performed under left-handed circularly polarized (LHC) and right-handed circularly polarized (RHC) light.
• Parametric studies were conducted to evaluate the effect of geometric parameters like rotation angle and disk radius.

Main Results:

• The proposed twisted multilayer double semi-disc structure achieved a high extinction ratio of up to 900.
• A broad operational bandwidth, defined by an extinction ratio greater than 10, was observed to be between 50-160 nm.
• The broadband position, bandwidth, and extinction ratio were found to be sensitive to geometric parameters, indicating tunability.

Conclusions:

• The twisted multilayer double semi-disc nanostructure is a promising design for efficient broadband circular polarizers.
• The study clarifies the role of plasmon electromagnetic resonance in achieving the observed polarization control.
• The demonstrated tunability through geometric parameters facilitates the optimization of these polarizers for specific applications.