Riabenko, Iuliia, School of radiophysics, biomedical electronics and computer systems, V. N. Karazin Kharkiv National University, 4 Svobody Sq., Kharkiv, 61022 Ukraine; Institute of Physical Chemistry, Abbe Center of Photonics, Friedrich Schiller University Jena, Albert-Einstein-Straße 9, 07745 Germany, Ukraine