Layer interface roughness effects in the coherent intraband transitions ofexcitons in quantum well structures

Using photoluminescence spectroscopy we study the effects of exciton locali zation and interface growth islands in the coherent intraband transitions b etween the exciton states associated with the first and second conduction s ubbands. We show that the growth islands can act as submicron quantum syste ms with distinct energy-level configurations. Our results show that these s ystems interact differently with an intense infrared laser, causing a nearl y two-dimensional medium with spatially modulated optical properties. We al so show that the exciton localization enhances the coherent intraband trans itions and discuss how these transitions can be used to study morphology of the interfaces between quantum well layers.