  The results of investigation of extremely compressed wave packet-light bullet
(LB) penetration through an air gap under single-pulse femtosecond Mid IR
filamentation in LiF are presented. It is revealed by the laser coloration
method and from numerical simulations that a single-cycle LB, which was formed
before an air gap up to 0.5 mm width, completely recovered after passing some
distance in LiF after the gap. This distance increases nonlinearly with the gap
width and LB pathway before the gap. LB in the air gap has a strongly
convergent wave front with focusing radius of 20-100 {\mu}m and its divergence
after the waist is considerably less than that of Gaussian beam.
