  Integrating equations of particle-number and energy-momentum conservation and
Maxwell field equations, we study the oscillation and drift of electron and
positron pairs coherently with fields after these pairs are produced in
external electromagnetic fields. From the electric current of oscillating
pairs, we obtain the energy spectrum of electromagnetic dipole radiation. This
narrow spectrum is so peculiar that the detection of such radiation can
identify pair production and oscillation in strong laser fields. We also obtain
the energy spectrum of gravitational quadrapole radiation from the
energy-momentum tensor of oscillating pairs and fields. Thus, we discuss the
generation of gravitational waves on the basis of rapid development of strong
laser fields.
