Gaseous plasmonic structures for gigahertz and low terahertz wave manipulation
Keywords: Mechanical Engineering.

Electromagnetic wave extinction and manipulation based on periodic structures have been studied for a long time. Lord Rayleigh extensively investigated the reflective properties of one-dimensional multilayer periodic structures in 1887. A century later, E. Yablonovitch and S. John published seminal work on the properties of photonic crystals and discussed the presence of photonic bandgaps in their transmission spectrum. Only recently, in 2007, O. Sakai experimentally verified that a two-dimensional array of microplasmas can act as a tunable photonic crystal with electromagnetic properties not achievable with bulk plasmas. In this dissertation the potential of generating tunable periodic plasma structures operating in the microwave and low terahertz region of the electromagnetic spectrum is investigated. Gaseous plasmonic crystals have significant advantages over conventional dielectric or metallic structures. Tunability is achieved by varying the electron plasma density and the momentum transfer collision frequency. Furthermore, fast reconfigurability of the plasma array can be achieved by powering on or off some of the elements of the crystal and the structure is transparent when the device is unpowered. The development of plasma photonic crystals has the potential to contribute to the fields of high-power microwave applications, telecommunication, sensors, photonic integrated circuits, military devices and many others. This work offers an introduction to the relevant properties of plasmas and photonic crystals emphasizing the superior properties observed in gaseous plasma periodic structures studied through computational simulations. Transverse electric and transverse magnetic polarizations are considered and tunable features of the transmission spectrum are discussed. In particular, the coupling between plasmonic and photonic features through Fano resonances is explored. An experimental platform operating in the 2 to 18 GHz microwave range in the S to Ku bands is developed to study the transmission of such plasma arrays. The device, built using discharge lamps, is configured to verify the presence of this coupling and to further explore the tunability of bandgaps and cutoffs in the transmission spectrum of the device. A higher frequency device operating in the low terahertz region of the electromagnetic spectrum is also considered. A continuous laser-based method is used to ionize cesium vapor in order to generate a periodic array of dense plasma filaments to meet the requirements necessary for millimeter wave manipulation. The laser ionized cesium plasma is characterized by optical emission spectroscopy in order to verify the plasma density regime and its spatial distribution across a single plasma filament at various experimental conditions. The electromagnetic properties of the periodic structure are investigated using a state-of-the-art terahertz spectrometer. Although the collisionality of the plasma precludes the presence of photonic bandgaps in this scaffold-less structure, highly tunable plasmonic extinction bands are observed up to 200 GHz