High-efficiency surface plasmon meta-couplers: concept and microwave-regime realizations

Area of Science:

• Optics and Photonics
• Metamaterials
• Plasmonics

Background:

• Traditional methods for exciting surface plasmon polaritons (SPPs) and spoof SPPs using gratings or prism couplers suffer from low efficiency.
• These limitations stem from SPP decoupling into free space and unavoidable surface reflections, hindering applications in photonics.

Purpose of the Study:

• To propose and demonstrate a new, highly efficient scheme for exciting SPPs and spoof SPPs.
• To overcome the limitations of conventional SPP excitation devices.

Main Methods:

• Numerical simulation of a transparent gradient metasurface meta-coupler.
• Fabrication of a meta-coupler for microwave frequencies.
• Experimental validation using near-field and far-field measurements.

Main Results:

• Numerical simulations predicted an inherently high excitation efficiency of approximately 94% for the metasurface coupler.
• Experimental results demonstrated a spoof SPP excitation efficiency of approximately 73% in the microwave regime.
• The achieved efficiency is several times higher than that of existing devices.

Conclusions:

• The proposed transparent gradient metasurface provides a high-performance solution for spoof SPP excitation.
• This advancement can drive the development of novel plasmonic devices for enhanced light-matter interactions, especially at low frequencies.