Resonant absorption of incident electromagnetic waves in collisional inhomogeneous plasma slabs

Bowen Li,Zhibin Wang,Qiuyue Nie,Peiqi Chen,Aohua Mao,Xiaogang Wang

doi:10.1063/1.5113689

Bowen Li, Zhibin Wang + Show 4 more

Open Access

https://doi.org/10.1063/1.5113689

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Abstract

Resonant absorption is a process that electromagnetic (EM) energy is converted to plasma energy with a mode conversion on the resonant layer where the incident EM wave frequency equals to the local frequency of a plasma normal modes. With a finite collision between charged and background neutral particles in a plasma, the plasma oscillation is dissipated to widen the resonance layer and heat the plasma. In this work a modified scattering matrix methods (SMM) are applied to study the effects of the collision frequency, incident angle, and plasma thickness on resonant absorption. We analyze the energy absorption caused by resonance in comparison with collisional absorption for different parameters. It is found that the resonant absorption dissipates about nearly half of the incident EM energy in an overdense inhomogeneous plasma when the collision is weak, and the rest half portion is reflected. If the collision is strong, however, the collisional absorption is then more significant than the resonant and affects the entire wave propagation process.

Highlights

Propagation properties of electromagnetic (EM) waves in subwavelength plasma slabs are getting more attentions in recent years due to its simplicity for understanding features of wide applications in microwave diagnostics,1 plasma-wave interactions,2,3 and so on
Mode conversion with resonant absorption is a process that EM wave is transformed to ES plasma mode and be dissipated by collisions between electrons and neutral particles
The resonant absorption process is affected by the collision rate, incident angle, plasma slab width and plasma density profile

Summary

INTRODUCTION

Propagation properties of electromagnetic (EM) waves in subwavelength plasma slabs are getting more attentions in recent years due to its simplicity for understanding features of wide applications in microwave diagnostics, plasma-wave interactions, and so on. With an inhomogeneous density profile, if the plasma slab thickness is comparable to or less than the incident EM wavelength, resonant absorption may occur and cause transmission and absorption of waves.. In the extremely thin resonant layer, the electric field has an approximate singularity if the collision can be ignored. This property is often applied to metamaterials as wave concentrators, polarization manipulation, and so on. Effects of the collision on the mode conversion and energy absorption in the resonant absorption layer should be investigated further in certain applications. Modified scattering matrix methods (SMM) are applied to simulate the process, and analyze effects of the collision, incident angle, and plasma slab thickness on waves in subwavelength plasma slab. The ratio of the resonant absorption to the incident EM energy is calculated

MODEL ANALYSIS

MODIFIED SMM SOLVER

NUMERICAL RESULTS AND DISCUSSIONS

Properties of fields in plasma slab

Properties of resonant energy absorption

CONCLUSIONS