| Abstract [eng] |
One of the essential reasons for the attractiveness of terahertz frequency (THz) radiation is the increasing use of THz imaging systems. In order to improve and expand their application capabilities, systems must be designed as compact and convenient-in-use as possible. Although most of the attention so far has been dedicated to the miniaturization of active components, passive optical components received significantly less attention. Aiming to reduce the dimensions of THz imaging systems, bulky optical components can be replaced by thin, flexible and compact diffractive optical elements. This thesis describes three options for developing alternative components. First of all, carbon-based materials were employed. A thin and flexible graphite zone plate with cross-shaped apertures was developed and studied. Also, the potential of graphene for creating compact optical elements have been investigated. It has been demonstrated that metasurfaces made of thin and flexible steel foil with inverted split-ring resonators can focus the THz beam in case of mechanical deformation and also are suitable for use in polarization resolved THz imaging. A nonparaxial THz imaging system has been developed using exclusively silicon-based optics via fabrication of thin Fresnel, Airy, Bessel or Fibonacci lenses. It has been shown that using silicon diffraction optics it is possible to generate structured THz light in the form of an Airy beam. This property enables imaging of objects in the presence of an obscure obstacle and opens a possibility to investigate properties of graphene layers. Digital THz holography is demonstrated, and a method to improve the quality of the obtained THz holographic images using a 2- and 4-step phase shift method is presented. |
