Plasmonic Half-wave Plate at the Theoretical Limit of Polarization Conversion Efficiency using Toroidal Metasurfaces

Po-sheng Huang^1*, Amir Hassanfiroozi¹, Pin Chieh Wu¹

¹Department of Photonics, National Cheng Kung University, Tainan, Taiwan

* Presenter:Po-sheng Huang, email:louis19950128@gmail.com

Anisotropic metasurfaces working in the cross-polarization state has found wide applications in wavefront engineering, quantum optics, and imaging systems. However, their low polarization conversion efficiency highly constrains to practical applications. In this work, we innovate an array of single layer plasmonic metasurface with linear cross polarization conversion efficiency numerically as well as experimentally reaching ~24%, which is comparable to the theoretical limit. Based on the numerical investigation, such high polarization conversion efficiency is arose from the introduction of toroidal dipolar resonance. In addition, our plasmonic metasurface is capable of generating the toroidal resonance under either x- or y-polarized illumination, offering a promising channel for developing polarization-independent high-performance flat optical components and systems. The proposed plasmonic metasurface can be a promising candidate for real applications such as bio-chemical sensing, nano-laser, polarization converters, and nonlinear optics.

Keywords: Toroidal Metasurface, Cross Polarization Conversion, Theoretical Conversion Limit