Photoluminescence and pump-probe spectroscopy of Bragg and off-Bragg quantum wells

In this paper we report on the investigation of radiatively coupled quantum wells in periodic quantum well (PQW) structures. The experimentally determ ined mode structure and reflectivity spectra at the Bragg resonance as well as off Bragg can be successfully modeled by linear dispersion theory. Meas urements of the photoluminescence in a magnetic field show increased mode s plitting characteristic of the enhanced radiative broadening of the exciton ic resonance. In pump-probe measurements of the nonlinear transmission near the Bragg resonance, we find a large increase in transmission at the low e nergy side of exciton resonance. This optical gain is observed only for the duration of the pump pulse.