Tuesday, October 9, 2018
Abstract-Terahertz Switching Focuser Based on Thin Film Vanadium Dioxide Zone Plate
Petr M. Solyankin, Mikhail N. EsaulkovIgor, A. ChernykhIvan, V. Kulikov, Maxim L. Zanaveskin, Andrey R. Kaul, Artem M. Makarevich, Dmitrii I. Sharovarov, Oleg E. Kameshkov, Boris A. Knyazev, Alexander P. Shkurinov,
In this paper we propose a switchable focuser device based on a Fresnel zone plate (FZP) structure for terahertz (THz) applications. Each FZP contains rings, etched in thin VOfilm with the designed focal lengths of 50 and 100 mm for 3.7THz frequency. Temperatureinduced VO phase transition leads to the change in dielectric susceptibility of the material, which allows one to switch on and off the focusing properties of the device. The devices were tested with radiation of 3.1 and 3.7 THz emitted by quantum cascade lasers. Experimental results were compared with numerical simulations. In this article we compare the FZP based on VO films with different properties and show that a thicker VO film reveals higher focusing efficiency, while a thinner one reveals a higher modulation ratio for the peak intensity at the focal point of FZP. We demonstrate experimentally the near-diffraction-limited size of the beam in the focal point of the device. Switching between two phase states of the VO films results in up to the 38-fold change of intensity in the focal point.