A fully tunable plasma photonic crystal is used to control the propagation of free space electromagnetic waves in the S to X bands of the microwave spectrum. An array of discharge plasma tubes forms a simple square crystal structure with the individual plasma dielectric constant tuned through variation in the plasma density. We show, through simulations and experiments, that transverse electric mode bandgaps exist, arising from the positive and negative dielectric constant regimes of the plasma, and that the respective bandgap frequencies can be shifted through changing the dielectric constant by varying discharge current density.

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Waveguiding and bending modes are investigated in a fully tunable plasma photonic crystal. The plasma device actively controls the propagation of free space electromagnetic waves in the S to X band of the microwave spectrum. An array of discharge plasma tubes form a square crystal lattice exhibiting a well-defined bandgap, with individual active switching of the plasma elements to allow for waveguiding and bending modes to be generated dynamically. We show, through simulations and experiments, the existence of transverse electric (TE) mode waveguiding and bending modes.

The integration of gaseous plasma elements into a microwave photonic crystal band gap cavity structure allows for active tuning of the device. An alumina rod array microwave photonic crystal waveguide resonator is simulated and characterized through finite difference time domain methods. A gaseous plasma element is integrated into the cavity structure and the effect of plasma density on the transmission properties of the structure is investigated. We show, through both simulations and experiments, that the permittivity of the plasma can be adjusted to shift the peak resonance to allow for both switching and tunability of transmission. The experimentally measured peak shifts in transmission are compared to those simulated and the electron density of the gaseous plasma element is calculated and compared to values determined from the measured discharge current density.

[1] A high-resolution three-dimensional numerical simulation is performed with the parallel, unstructured grid SUNTANS model to study the spatiotemporal dynamics of turbulent mixing in a shallow, macrotidal salt wedge estuary that experiences periodic mixing and strong stratification. Unresolved vertical mixing is parameterized with the k − kl closure scheme with the Canuto-A stability functions based on a careful comparison of multiple two-equation closure schemes and stability functions via the generic length scale approach. The predictions of velocity, salinity, Richardson number, and Reynolds stress are in good agreement with field observations, and the top and bottom salinity predictions achieve skill scores of 0.86 and 0.91, respectively. The model shows that the salt wedge starts to strengthen upstream at the beginning of weak ebb and gradually expands downstream during the weak tide. Mixing is most active along a density interface during the weak ebb, while it is most active in a bottom mixed layer during weak flood, consistent with the findings inferred from the observations. Stratification decays during the strong ebb in a mixing event along the horizontal extent of the salt wedge while it is also being advected offshore. Local mixing is shown to account for roughly half of the decay rate of the stratification in this process. Numerical experiments are performed to investigate the response of stratification and mixing to changes in the magnitude of the buoyancy. High sensitivity is shown under intermediate levels of stratification that occur in the real system, which becomes considerably weaker under more extreme conditions.