Surface plasmon generation and field intensification by sub-wavelength double-ring structure of plasmas

Binnan Qu,Bowen Li,Xiaogang Wang

doi:10.1063/1.5135024

Abstract

In this paper, we propose a plasma structure that can effectively enhance surface plasmon resonance and achieve significant local field enhancement. For specific incident wave frequencies, two plasma rings and a vacuum layer between them can form a metal-insulator-metal (MIM) waveguide, which can resonant as a Fabry–Perot cavity and couple the incident wave energy to the vicinity of the plasma ring slit, and thus effectively enhance the localized surface plasmon resonance inside the plasma ring. The simulation results show that, by adjusting the thickness and angle of the outer plasma ring, the average electric field of the incident wave inside the structure can be increased by a factor of 9. Moreover, at the same plasma frequency and incident wave band, the local field enhancement of the double-ring structure is better than that of a circular ring structure or a circular ring structure with a slit. We have also analyzed the physical mechanism of field enhancement and calculated the dispersion relation of surface plasmon polaritons in the Fabry–Perot cavity. The results are in good agreement with the theory of the MIM waveguide cavity.

Highlights

Surface plasmon (SP), as a type of surface waves generated on an interface between the plasma and the dielectric, can effectively confine energy near the interface
We found that when the resonance mode of the localized surface plasmon (LSP) in the plasma ring is the dipole field, the field enhancement in the ring is the most intensive
We have proposed and optimized subwavelength double-ring plasma (DRP) structures

Summary

INTRODUCTION

Surface plasmon (SP), as a type of surface waves generated on an interface between the plasma and the dielectric, can effectively confine energy near the interface. Previous studies on surface plasmons mainly focused on nanoscales for interactions between metal nano-structures and visible light In those cases, the plasma frequency of metals is much higher than that of visible light (the overdense plasma condition), while the characteristic size of the metal structure is much less than that of visible light wavelength (the subwavelength condition). The surface plasmon wavelength comes down to 51 nm (less than 8% of the free space wavelength) On this basis, Cui and He19 introduced a resonant cavity to enhance the transmission efficiency through certain metallic nanoslits. Cui and He19 introduced a resonant cavity to enhance the transmission efficiency through certain metallic nanoslits One can apply such a structure to the microwave regime for signal intensification, by a subwavelength slit insertion in a plasma ring covering a receiving antenna, with another plasma ring in front of the slit to make a Fabry–Perot cavity for the incident signals..

MODEL OF SIMULATION

RESULTS AND DISCUSSIONS

CONCLUSIONS