  It is demonstrated theoretically that the circularly polarized irradiation of
two-dimensional conducting systems can produce the composite bosons consisting
of two electrons with different effective masses (different charge carriers),
which are stable due to the Fermi sea of conduction electrons. As a result, the
optically induced mixture of paired electrons and normal conduction electrons
(the hybrid Bose-Fermi system) appears. Elementary excitations in such a hybrid
system are analyzed and possible manifestations of the light-induced electron
pairing are discussed for semiconductor quantum wells.
