| Description |
This dissertation presents a variety of Terahertz (THz) Waveguides. The presented waveguides, in terms of physical feature, are built along a core idea that adoption of planar layout in fabrication leads to exponential growth in device capabilities, akin to the growth in device capabilities based in electronics. On functional lines, the waveguides support wave propagation on a metal surface. Dielectrics tend to be lossy at THz and the loss parameters scale almost quadratically for most dielectrics. The loss in a propagating wave is minimized by utilizing the metal surface. Structuring the metal surface with a periodic array of apertures of subwavelength dimension allows a bound surface wave to be propagated as the wave decays into the metal evanescently. This phenomenon is referred to as the coupling of a propagating wave to surface plasmon polariton (SPP) like mode at the interface of a structured metal surface and air. It is for this reason the propagating THz wave is often denoted as a Terahertz Surface Plasmon (TSP). Similarly, complimentary structures that do not perforate but stand on a metal surface also allow TSP. Wavelength of the TSP can be controlled by changing the dimension of these apertures/structures as the dispersion relationship of the medium depends on the geometrical size. This engineering capability has been exploited in creating all the waveguides presented within this thesis. The waveguides presented are categorized based on the fabrication technique. Each technique is unique in its own regard and can be selected based on functional needs. A commonly adopted process of iv laser ablation covers a wide set of waveguides presented here. In one of the waveguides fabricated using the ablation technique, the role of disorder is discussed. The waveguide with introduction leads to observance of a localized mode with spectral and spatial features like Anderson localized modes of photons. This is the first report of a localized mode at THz frequency. Three-dimensional rapid prototyping involving a 3D printer is used to create waveguides with a complex layout that can allow for multiplane signal routing. This is also the first proposition of the usage of 3D printing in development of THz device realm. |
