1. Institute of Physics, Kazimierz Wielki University, Powstańców Wielkopolskich 2, 85-090 Bydgoszcz, Poland
2. Faculty of Technical Physics, PUT, Piotrowo 3, 60-965 Poznań, Poland
3. Institute of Physics, Technical University of Łódź, Wólczańska 219, 93-005 Łódź, Poland