  The conventional picture of the light amplification by stimulated emission of
radiation (laser) is broken under the ultrastrong interaction between the
electromagnetic fields and matter, and distinct dynamics of the electric field
and of the magnetic one make the "laser" qualitatively different from the
conventional laser, which has been described simply without the distinction.
The "laser" in the ultrastrong regime can show a rich variety of behaviors with
spontaneous appearance of coherence. We found that the "laser" generally
accompanies odd-order harmonics of the electromagnetic fields both inside and
outside the cavity and a synchronization with an oscillation of atomic
population. A bistability is also demonstrated in a simple model under
two-level and single-mode approximations.
