Multifrequency superscattering with high <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>Q</mml:mi></mml:math> factors from a deep-subwavelength spoof plasmonic structure

Abstract

Superscattering is usually described as a scattering cross section, induced by degenerate resonances, that exceeds the single-channel limit of a subwavelength scatterer. It has important applications in sensing, bioimaging, and emissions amplification. The quality factor $(Q$ factor) of superscattering plays a significant role in the performance of these practical applications, yet it has not been extensively investigated. Here, we used a spoof plasmonic spiral structure on a deep-subwavelength scale to achieve multifrequency superscattering with a high $Q$ factor. Based on eigenmode analysis, we found that those eigenmodes supported in the spoof plasmonic spiral structure not only had very high $Q$ factors, but also exhibited natural degeneracy at high spiral degrees. We also discuss the influence of structural variation and practical material loss of the spiral structure on the performance of the superscattering. Results indicated that multifrequency, high-$Q$ superscattering was refractory to the structural variation and practical material loss of the spiral structure. Our work should anticipate future sensitive and versatile optical devices based on high-$Q$ superscattering from the microwave to the terahertz wave band.