Chiral Devices for Terahertz Waves Based on Tunable Metamaterials

There are exceptional advantages in the region where Terahertz (THz) frequency takes place that could be identified as; a non-ionizing bio-innocuous property, transparent characteristics in cardboard or textiles, and extremely discriminating absorption spectral lines which can provide a “genetic code” of various bio-materials. [1,2]. The resonant effects at various terahertz frequencies that were displayed by metamaterials have created to accomplish a very important situation. Metamaterials are virtually desirable platforms for investigating chiral effects. In order to enhance these effects, producing the tunable chiral devices attracted lots of attention. Among the phase change materials for chiral metamaterials, graphene is a promising candidate due to its astonishing properties specifically in the THz and far infrared region. In this study, a chiral metamaterial gammadion structure is designed and fabricated on both sides of the sapphire substrates. A commercial COMSOL and CST Microwave Studio programs are used to design and optimize the chiral metamaterial. Numerical simulations are based on the interaction of the chiral structure with linearly and circularly polarized light. In the experimental side, a resistive evaporation and dc magnetron sputtering method is used for the deposition of gold and Sb2Se3 films respectively. A single layer graphene is used, that is grown on a copper foil by chemical vapor deposition. The thin graphene layer transferred on the Sb2Se3 coated sapphire substrates. The conventional UV lithography and ion beam etching techniques are used for patterning process. The THz characterization measurements were performed in order to assess the THz frequency response and to demonstrate the dynamically tunable chiroptical response using optical pumping [3,4]. The active polarization manipulation capability of the Sb2Se3/graphene chiral metamaterial with frequency tunability are investigated both numerically and experimentally.XVI Photonics Workshop : Book of abstracts; March 12-15, 2023; Kopaonik, Serbi

Comparison of photocatalytic properties of TiO

Efficiency of solar panels degrades as a result of organic contamination such as airborne particles, bird droppings and leaves. Any foreign object on photovoltaic panels reduces the sunlight entering the absorbing surface of the solar panels. Since this leads to a major problem decreasing in energy production, solar panels should be cleaned. The self-cleaning method can be preferred. There are some methods to clean the surface of solar panels. Among the self-cleaning materials, TiO2 is the most preferable ones because of its powerful photocatalytic properties. In this study, photocatalytic TiO2 were produced in two different nanostructures: nanofibers and thin films. TiO2 nanofibers were successfully produced by electrospinning. TiO2 thin films were fabricated by reactive magnetron sputtering technique. Both TiO2 nanofiber and thin film structures were heat-treated to form TiO2 in anatase phase at 600 °C for 2 h in air. Then, they were evaluated by SEM analyses for morphology, X-ray diffraction (XRD) analyses for phase structures, X-ray photoelectron spectroscopy (XPS) for the chemical state and atomic concentration, and UV-spectrometer for photocatalytic performance. The results indicate that photocatalytic and transmittance properties of TiO2 thin films are better than those of nanofibers. Consequently, TiO2 based thin films exhibit better performance for solar cell applications due to the surface cleanliness