Abstract
Wave propagation is observed through a negative permeability metamaterial immersed in gaseous plasma. A 3D array of split ring resonators (SRR) is enveloped by an inductively heated argon plasma with a nominal plasma frequency of 2.65 GHz. Transmission spectra show electromagnetic waves traverse the composite medium from 1.3–1.7 GHz for which the permeability of the SRRs and the permittivity of the plasma are simultaneously negative. Only surface waves and evanescence are observed outside this frequency band. The edge of the transmission band also shows negative group velocity, albeit with high wave attenuation. The free electron density of the plasma is coupled to the inductive heating, allowing dynamic reconfiguration of the metamaterial’s frequency band and wave impedance.
Highlights
Many researchers have reported electromagnetic properties based on this configuration[6,7] for which the ensemble of electric dipoles creates an effective permittivity with εwire < 0 and the magnetic resonance of the split ring resonators (SRR) gives an effective medium with range of applications[8,9,10] including cloaking devices, optical dμeSRteRc
The effective permeability of the SRR medium is extracted from the magnitude and phase of S21 using well-known methods[20,21]
The material shows bands of negative permeability that correlate with the ensemble resonances of the SRRs
Summary
At lower frequencies the electromagnetic (EM) wave is evanescent - due to negative plasma permittivity when ω < ωpe - and the measured transmission is −20 dB less than through free space. There is some transmission (−10 dB) in the control experiment near 1.2 GHz. This is the frequency for which a surface plasma polariton[22,23] is expected to propagate along the interface between the plasma and the TMM3 substrate[24].
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