Properties of arrays of microplasmas: application to control of electromagnetic waves

Microplasma arrays (MAs) are being investigated as a method to control the propagation of electromagnetic waves. The use of MAs as an electromagnetic wave controlling material is attractive as the electrical properties of MAs can be rapidly changed through combinations of the choice of operating conditions (e.g. pressure, gas mixture), the spatial distribution of the plasma and applied voltage waveforms. In this paper, results from a computational investigation of the plasma properties of small arrays of microplasmas are discussed. The model systems are arrays of microplasmas sustained in rare gases at pressures of up to 100 Torr in a sealed chamber. Individual plasma cells are ≈100 μm in size. Pulsed dc voltage waveforms having widths of 30 ns are applied at repetition rates of up to 10MHz. The cross-talk between plasma cells was investigated, as well as the consequences of gas heating and sequencing of the pulses. We found that even without physical barriers between the plasma cells to control cross-talk between cells, the individual character of each cell can be retained; however the plasma cells were not completely independent. The diffusion of metastable excited atomic states and small fluxes of ions did enable adjacent cells to operate at lower voltages. The ability to control microwave propagation through waveguides was computationally investigated by placing a MA inside a standard waveguide and examining the resulting transmission coefficients. We found that for frequencies of tens to 100 GHz, the transmitted power could be controlled by the spatial distribution of the MA cells with respect to the modal structure of the wave.