Metamaterials for remote generation of spatially controllable two dimensional array of microplasma

Abstract

Since the initial demonstration of negative refraction and cloaking using metamaterials, there has been enormous interest and progress in making practical devices based on metamaterials such as electrically small antennas, absorbers, modulators, detectors etc that span over a wide range of electromagnetic spectrum covering microwave, terahertz, infrared (IR) and optical wavelengths. We present metamaterial as an active substrate where each unit cell serves as an element for generation of plasma, the fourth state of matter. Sub-wavelength localization of incident electromagnetic wave energy, one of the most interesting properties of metamaterials is employed here for generating high electric field to ignite and sustain microscale plasmas. Frequency selective nature of the metamaterial unit cells make it possible to generate spatially localized microplasma in a large array using multiple resonators. A dual resonator topology is shown for the demonstration. Since microwave energy couples to the metamaterial through free space, the proposed approach is naturally wireless. Such spatially controllable microplasma arrays provide a fundamentally new material system for future investigations in novel applications, e.g. nonlinear metamaterials.

Figure 1. Schematic representation of remote generation of plasma using metamaterials.

Radiated microwave power from the antenna couples to the metamaterial at its resonance frequency and generates a high electric field inside the capacitive gap of each metamaterial unit cell (i.e., C shaped split ring resonator). This ignites and sustains plasma that is localized in the sub-wavelength capacitive region of each metamaterial unit cell.

Figure 2

(a) Photograph of a dual frequency metamaterial board, (b) measured and simulated microwave power transmission results for the metamaterials showing two resonance frequency at 2.1 GHz and 2.45 GHz respectively, the inset shows simulated electric field at resonance frequencies in the metamaterial structure – only the resonator with resonance at frequency of incident radiation shows maximum electric field (c) photograph of the patch antenna at 2.1 GHz used for microwave radiation, and (d) simulated and measurement results of the 2.1 GHz patch antenna, inset shows simulated antenna power radiation pattern.

Figure 3. Wireless plasma generation in dual frequency metamaterials in argon gas at pressure of 40 Torr.

Plasma is generated in only array of resonators working at (a) 2.1 GHz and (b) 2.45 GHz.

Figure 4. Metamaterial board of 10 × 10 elements generating plasma at atmospheric pressure and microwave frequency of 2.45 GHz.

Plasma is generated in 90 elements out of 100 elements. Photograph is taken through a metal mesh.