Photoreflectance investigation of InAs quantum dashes embedded in In 0.53 Ga 0.47 As ∕ In 0.53 Ga 0.23 Al 0.24 As quantum well grown on InP substrate Photoluminescence and photo-modulated reflectance spectra of ion-implanted GaAs/AlGaAs coupled quantum wells Quasiphase matched surface emitting second harmonic generation in periodically reversed asymmetric GaAs/AlGaAs quantum well waveguide Photoreflectance ͑PR͒ spectra of GaAs/AlGaAs multiple quantum well waveguides at room temperature were investigated. In addition to the allowed and symmetry forbidden transitions between confined states, a number of transitions involving the unconfined states were also observed. The coupling between the multiple wells ͑miniband dispersion͒ of both confined states and unconfined states ͑above barrier band gap͒ were reported. By using the propagation-matrix method, the energies for both confined transitions and unconfined transitions were calculated and shown to agree with the experimental values determined by fitting the PR spectra to the theoretical line shape expression.