A sink enables subwavelength focusing by absorbing the converging wave at the focal point, preventing the creation of a diverging wave. We demonstrate in this paper that plasmas can behave as a microwave sink. This requires coupling the converging wave to localized surface-plasmon resonances, enabling perfect coherent absorption. We introduce a finite-difference time-domain body-of-revolution model, which couples Maxwell’s equations with a fluid description of the plasma. Our results indicate that the plasma can indeed act as a microwave sink for both continuous and broadband converging waves. The plasma parameters required to achieve this behavior are achievable experimentally, with plasma ignition taking place inside a cylindrical tube. The obtained field intensification and subwavelength focusing may provide a means to enhance nonlinear plasma ignition in plasmas sources.

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• Angular momentum of light
• Phase shift
• Plasma optics
• Plasmonics
• Scattering theory
• Surface plasmons
• Metamaterials
• Microwave techniques