1. Laboratory of Terahertz Spectroscopy, Center for Photonics and 2D Materials, Moscow Institute of Physics and Technology, 141701, Dolgoprudny, Moscow Region, Russia
2. Institute of Physics, Czech Academy of Sciences, 18200 Prague 8, Czech Republic
3. Faculty of Mathematics and Physics, Charles University, 12116 Prague 2, Czech Republic
4. Sobolev Institute of Geology and Mineralogy, 630090 Novosibirsk, Russia
5. Novosibirsk State University, 630090 Novosibirsk, Russia
6. 1. Physikalisches Institut, Universität Stuttgart, 70569 Stuttgart, Germany