1. Institute of Physics, University of Zielona Góra, Prof. Szafrana 4a, Zielona Góra 65-516, Poland
2. Faculty of Physics, Hanoi National University of Education, 136 Xuan Thuy, Cau Giay, Hanoi 10000, Vietnam
3. Institute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam