Active Polarization Control with a Parity-Time Symmetric Plasmonic Resonator

TL;DR

This paper demonstrates a nanoscale plasmonic aperture that uses parity-time symmetry to actively control light polarization, enabling tunable waveplate and polarization rotation functionalities with high efficiency and reconfigurability.

Contribution

It introduces a novel, low-threshold, reconfigurable polarization control device based on a parity-time symmetric plasmonic resonator, advancing nanoscale polarization manipulation technology.

Findings

Achieves polarization control without signal loss.

Enables continuous tuning of ellipticity and rotation.

Operates with realistic loss and gain levels.

Abstract

Control of the polarization state of light is essential for many technologies, but is often limited by weak light-matter interactions that necessitate long device path lengths or significantly reduce the signal intensity. Here, we investigate a nanoscale plasmonic aperture capable of modifying the polarization state of far-field transmitted light without loss in the probe signal. The aperture is a coaxial resonator consisting of a dielectric ring embedded within a metallic film; parity-time ($\mathcal{PT}$) symmetric inclusions of loss and gain within the dielectric ring enable polarization control. Since the coaxial aperture enables near-thresholdless $\mathcal{PT}$ symmetry breaking, polarization control is achieved with realistic levels of loss and gain. Exploiting this sensitivity, we show that the aperture can function as a tunable waveplate, with the transmitted ellipticity of circularly polarized incident light changing continuously with the dissipation coefficient from $\pi/2$ to 0 (i.e. linear polarization). Rotation of linearly polarized light with unity efficiency is also possible, with a continuously-tunable degree of rotation. This compact, low-threshold, and reconfigurable polarizer may enable next-generation, high-efficiency displays, routers, modulators, and metasurfaces.