We discuss a computational modeling study of surface plasma generation by spoof surface plasmon polariton (SSPP) mode excitation of a corrugated metal surface. The SSPP mode is a highly localized electromagnetic wave propagating along the interface between a conductor and dielectric. The corrugations are defined by an array of rectangular cavities (comb structures) in the metal at the location of the interface. Spoof plasmon resonances occurring at each cavity couple with one another at the interface to produce localized surface wave structures whose wavelength can be much smaller than the incident wave. The electromagnetic wave structure for a finite length of the interface (metasurface) is analytically estimated and its correlation to the resonance frequency of the infinite metasurface is studied numerically. Strong local enhancement of the electromagnetic fields at the metasurface is used to initiate the plasma breakdown of pure argon gas at 10 Torr. Confined microdischarges produced initially at each of the comb structure evolve rapidly to create an extended structure of high density ~10 19 m −3 surface plasma whose properties are comparable to surface streamers generated in dielectric barrier discharges.
We present a multi-physics model of combustion ignition phenomena in an atmospheric pressure hydrogen-air mixture ignited by a microwave surface plasma discharge. The surface plasma is generated over a resonant metasurface structure that provides sufficient field intensification to break down and sustain a discharge. Specifically, a surface electromagnetic (EM) wave mode known as the spoof surface plasmon polariton (SSPP) is excited to yield a hybrid resonance that results from coupling of cavity and surface EM wave modes. Motivated by the need for a large, volumetric ignition kernel for applications in combustion ignition, we numerically demonstrate the volumetric surface plasma discharge enabled by the use of this particular EM wave mode in a high pressure operating regime. We discuss the transient evolution of a centimeter scale plasma kernel and subsequent ignition kernel formation. High density combustion enhancing radical species (O, H, OH) are produced throughout the bulk plasma, which leads to successful ignition. A parametric study shows that the large size of a plasma kernel is attributed to the shortening of ignition delay.
We demonstrate through numerical experiments and analytical calculations that extreme subwavelength gaps between two corrugated surfaces support high effective refractive index guided modes. The corrugated gap mode is of low loss because it does not rely on plasmonic currents induced inside a metal. This enables guided modes with a much higher effective refractive index than is possible in natural plasmonic materials. These high-index guided modes are incorporated as periodic slots in an opaque screen, which is then shown to support broadband highly transmitting modes at a certain oblique incidence angle in addition to the usual Fabry–Pérot resonances. This anomalously high transmission is the extension of the plasmonic Brewster angle to arbitrarily low frequency, controlled by the geometry of the corrugated slots. We demonstrate the preservation of the shape of a broadband low-frequency pulse transmitted through the slotted screen, opening up the possibility to use the structure for broadband energy squeezing applications in the GHz to THz regime.
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