Luminescent properties of Er3 - and Yb3 - co-doped CaF2 upconversion nanoparticles (UCNPs) were investigated in single particle and densely-packed states with a custom-built microscope. The single UCNPs exhibit linear depe
In this paper, we propose and experimentally demonstrate a vortex random fiber laser (RFL) with a controllable orbital angular momentum (OAM) mode. The topological charge of the vortex RFL can range from