1. Institute of Applied Electrodynamics and Telecommunications, Faculty of Physics, Vilnius University, Saulėtekio Av. 3, LT-10257 Vilnius, Lithuania
2. Department of Optoelectronics, Center for Physical Sciences and Technology, Saulėtekio Av. 3, LT-10257 Vilnius, Lithuania
3. Institute of Photonics and Nanotechnology, Faculty of Physics, Vilnius University, Saulėtekio Av. 3, LT-10257 Vilnius, Lithuania