  We develop a microscopic theory of a strong electromagnetic field interaction
with gated bilayer graphene. Quantum kinetic equations for density matrix are
obtained using a tight binding approach within second quantized Hamiltonian in
an intense laser field. We show that adiabatically changing the gate potentials
with time may produce (at resonant photon energy) a full inversion of the
electron population with high density between valence and conduction bands. In
the linear regime, excitonic absorption of an electromagnetic radiation in a
graphene monolayer with opened energy gap is also studied.
