Date of Award
Doctor of Philosophy (PhD)
Computer Engineering and Sciences
Brian A. Lail
In recent years, plasmonic resonant antennas have seen widespread consideration in many detection and chemistry applications due to their potential for enhancing and confining the emission and polarization of electromagnetic fields. Examples include optical couplers to ultra-compact photodetectors, high-resolution optical microscopy, enablers of single molecule Raman signal detection and heating elements that facilitate nanostructure growth. A wideband teardrop shape antenna coupled detector will illustrate in this dissertation. An asymmetric cross-bowtie antenna is investigated for providing a broad circular polarized frequency response in the long wave infrared (LWIR). The asymmetric cross-bowtie antenna is constructed with two perpendicular bowtie antennas with differing arm lengths. The asymmetric cross-bowtie antenna is numerically analyzed using a finite element method (FEM) solver; Ansys High Frequency Structural Simulator (HFSS). The two perpendicular bowtie antennas, under illumination, provide a wide-band localized circularly-polarized field within a shared antenna feed-gap. At the center frequency of 28.3THz (10.6μm), a circularly-polarized state over 30% bandwidth is achieved. The antenna is then loaded with a metal-oxidemetal diode in order to design a circularly polarized antenna-coupled detector. A new analytical method of tuning the resonant frequency of optical microstrip patch antennas is presented. For this method, the changing of resonant frequency of microstrip patch antenna due to coupling additional reactance can be clearly determined. This method verifies that the TM10 resonant frequency increases by adding a ridge with variable width and height under the patch antenna. A range of resonant frequencies tuning from 20.75 to 32.4THz, by varying ridge width from 0 to 0.5µm and ridge height from 0.1 to 0.6µm are demonstrated. Low-loss planar transmission lines are required for integrated optical or plasmonic nanocircuits. Full characterization of these lines is necessary for designing nanocircuits. This dissertation will show a method to calculate the attenuation and propagation constants of a patch-antenna-coupled microstrip transmission line (MTL) at 28.3THz that is suitable for measurement implementation via near-field microscopy techniques. After illumination with a Gaussian beam, a standing wave is formed by the electric near field along the MTL observed at the metal-air interface. By fitting an analytical standing wave expression to the near-field standing wave, the attenuation and propagation constants are determined. With the MTL characterized, a similar technique can be applied to determine the input impedance of an unknown load fed by the MTL. The quantification of antenna impedance and transmission line parameters provide requisite information for improving impedance matching and collection efficiency. Polaritonic slot waveguides have been explored as a means of manipulating nanoscale fields to compete in the race for the sub-diffractional confinement of light. Hexagonal boron nitride (h-BN), when incorporated into hyperbolic-insulator-hyperbolic (HIH) configurations, is a strong contender, with its naturally occurring anisotropy allowing it to strongly confine and enhance local fields. However, while the volumetric phonon polaritons of h-BN have been widely used for these means, its hyperbolic surface phonon polaritons (HSPhPs) or D’yakonov polaritons contain untapped potential and are widely unused. In this dissertation, we qualitatively discuss the hybridization of fundamental hyperbolic surface phonon polariton modes in an HIH slot waveguide. The resulting symmetric dark, or lower mode, is then used to design a patch antenna, which shows possibilities for applying the familiar microstrip transmission-line approach of antenna design to this HSPhP antenna.
Miao, Shenjie, "Optical Nanoantenna Coupled Detector and Hybrid Surface Waveguide" (2020). Theses and Dissertations. 808.
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