  It is shown that delocalized vortex solitons in relativistic pair plasmas
with small temperature asymmetries can be unstable for intermediate intensities
of the background electromagnetic field. Instability leads to the generation of
ever-expanding cavitating bubbles in which the electromagnetic fields are zero.
The existence of such electromagnetic bubbles is demonstrated by qualitative
arguments based on a hydrodynamic analogy, and by numerical solutions of the
appropriate Nonlinear Schr\"odinger equation with a saturating nonlinearity.
