Subwavelength imaging using plasmonic lenses at terahertz frequencies
Lethbridge, Alta. : University of Lethbridge, Dept. of Physics and Astronomy
The effects of diffraction at terahertz frequencies limit the spatial resolution of imaging systems. One approach to achieve subwavelength resolution is near-field imaging using a subwavelength aperture, however, the low transmission through subwavelength apertures limits the sensitivity of this approach. Plasmonic lenses in the form of bullseye structures, consisting of a circular subwavelength aperture with concentric periodic corrugations, have demonstrated enhanced transmission and beam confinement. This thesis discusses the design criteria of plasmonic lenses optimized for 325 GHz. Fabrication for optical applications is traditionally achieved by nanolithography. Since the scale of plasmonic structures depends on the wavelength, precision micromilling techniques are well suited for terahertz applications. Theoretical simulations are obtained using a finite-difference time-domain solver and the performance the devices are evaluated using a customized terahertz testbed. The prospect of using plasmonic lenses in a terahertz imaging configuration for the diagnosis of cancer is also discussed.
Plasmonics , Terahertz , Surface plasmon polaritons , Extraordinary transmission , Bullseye lens , Micromilling , Subwavelength imaging