Coherent excitonic gain under resonant excitation in semiconductor quantum wells

Summary form only given. Strong resonant excitation of atoms can lead to Mollow spectra in saturation spectroscopy, with gain near the Rabi sidebands or with a coherent dip at the atomic resonance. In this paper we report experimental studies on the manifestation of Mollow spectra and especially gain in an excitonic system. We observe a spectrally sharp coherent excitonic gain in a semiconductor quantum well under strong resonant excitation. Theoretical analysis based on modified optical Bloch equations (MOBE) indicates that this coherent gain differs qualitatively from its counterpart in atomic systems and is a direct result of exciton-exciton interactions. Understanding the manifestation of Mollow spectra and gain in an excitonic system provides important insight into coherent optical interactions in semiconductors and is of importance in understanding recently observed parametric gain associated with exciton-polaritons in semiconductor microcavities.