  We consider the one-photon annihilation mechanism in a electron - positron
quasiparticle plasma (EPP) created from the vacuum in a strong subcritical
laser field due to the dynamical Schwinger mechanism. On the basis of a kinetic
theory approach we show that the secondary photons have a radiation spectrum
proportional to 1/k (flicker noise). This effect is very small for EPP
excitations in the optical spectrum but can reach quite observable values in
the gamma - ray region.
