  In this paper we analyze the properties of chirped optical X-shaped pulses
propagating in material media without boundaries. We show that such
("superluminal") pulses may recover their transverse and longitudinal shape
after some propagation distance, while the ordinary chirped gaussian-pulses can
recover their longitudinal shape only (since gaussian pulses suffer a
progressive spreading during their propagation). We therefore propose the use
of chirped optical X-type pulses to overcome the problems of both dispersion
and diffraction during the pulse propagation.
