Pulsed light beams in vacuum with superluminal and negative group velocities.
We study the group velocity of pulsed light beams in vacuum. Gouy's phase associated with the diffraction of transversally limited pulses can create a strong anomalous dispersion in vacuum leading to highly superluminal and negative group velocities. As a consequence, a focusing pulse can diverge beyond the focus before converging into it. The experimental feasibility is discussed.
Porras
Miguel A
MA
Departamento de Física Aplicada, ETSI Minas, Universidad Politécnica de Madrid, Madrid, Spain.
Gonzalo
Isabel
I
Mondello
Alessia
A