  We present the findings of high efficient light absorption in self-assembled
quantum wells (SQW) embedded in silicon microcavities that exhibit a
distributed feedback identified by the FIR transmission spectra. The excitonic
normal-mode coupling (NMC) is found to result in high efficient bound exciton
photoluminescence in the range of the Rabi splitting. The bound excitons at the
iron-boron pair and the erbium-related centers inserted in SQW are shown to
cause giant exchange splitting of the center multiplets as a result of the
strong sp-d and sp-f mixing in the absence of the external magnetic field. The
NMC regime is observed to reveal this exchange splitting in the angular
dependencies of the transmission spectra measured in the range of the Rabi
splitting that are evidence of the ODMR of the trigonal iron-boron pairs and
trigonal erbium-related centers.
