  We propose and analyze an efficient scheme for suppressing the absorption of
a weak probe field based on intersubband transitions in a four-level asymmetric
coupled-quantum well (CQW) driven coherently by a probe laser field and a
control laser field. By using the numerical simulation, we find that the
magnitude of the transient absorption of the probe field is smaller than the
three-level system based on the electromagnetically induced transparency (EIT)
at line center of the probe transition, moreover, comparing with the scheme in
three-level asymmetric double QW system, the transparency hole of the present
work is much broader. By analyzing the steady-state process analytically and
numerically, our results show that the probe absorption can be completely
eliminated under the condition of Raman resonance (i.e. two-photon detuning is
zero). Besides, we can observe one transparency window without requiring one-
or two-photon detuning exactly vanish. This investigation may provide the
possible scheme for EIT in solids by using CQW.
