Elena Stoykova, Ph.D., D.Sc. in physics and optics, and Ventseslav Sainov, Ph.D., D.Sc. in engineering and optics, are full professors in the Institute of Optical Materials and Technologies, Bulgarian Academy of Sciences. Marin Nenchev, Ph.D. in optics and D.Sc. in physics and engineering, is a full professor in the Technical University in Sofia.