info:eu-repo/semantics/doctoralThesis
TERAHERTZ QUASI-OPTICAL DEVICES FABRICATED BY 3D PRINTING
Autor
Arturo Hernandez Serrano
Institución
Resumen
"In this thesis we theoretically and experimentally demonstrate four novel devices working at the THz range. We present the first 3D printed GRIN lens. Our measurements demonstrate how these lenses operate within the di↵raction limit no matter what the polarization is, at least for the fre- quencies below 800GHz ( > 375μm). We also investigate the chromatic aberration. In addition, we experimentally demonstrate a novel 3D printed quasi-wollaston prism. The prism uses the birefringence induced in a sub-wavelength layered plastic-air structure that produces refraction in dif- ferent directions for di↵erent polarizations. The component was simulated using the finite-di↵erence-time-domain method, fabricated by 3D printing and subsequently tested by terahertz time-domain spectroscopy showing a polarization separation around of 23 for frequencies below 400GHz, ex- hibiting cross polarization power extinction ratios better than 1.6 ⇥ 10 3 at 200GHz. Chapter5 is dedicated to the examination of, as the best of our knowledge, the first 3D printed q-plate with continuous birefringence variation for the generation of cylindrical vector beams at terahertz frequencies.
Finally in chapter 6 we demonstrate a stepped- refractive-index convergent lens made of a parallel stack of metallic plates for terahertz frequencies based on artificial dielectrics. The lens consist of a non-uniformly spaced stack of metallic plates, forming a mirror-symmetric array of parallel-plate waveguides (PPWGs). The operation of the device is based on the TE1 mode of the PPWG. By varying the spacing between the plates, we can modify the local refractive index of the structure in every individual PPWG that constitutes the lens producing a stepped refractive index profile across the multi stack structure. These results show that this structure is capable of focusing a 1 cm diameter beam to a line focus of less than 4 mm for the design frequency of 0.18 THz."
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