  We present theoretical results of the calculations of optical functions for
Cu$_2$O quantum well (QW) with Rydberg excitons in an external homogeneous
electric field of an arbitrary field strength. Two configurations of an
external electric field perpendicular and parallel to the QW planes are
considered in the energetic region for discrete excitonic states and continuum
states. With the help of the real density matrix approach, which enables the
derivation of the analytical expressions for the QW electro-optical functions,
absorption spectra are calculated for the case of the excitation energy below
the gap energy.
