Interaction of Wannier-Stark ladders in GaAs-AlAs superlattices observed by electroreflectance.

Electroreflectance (ER) spectroscopy has been used to study the influence of an electric field on the optical properties of a strongly coupled GaAs-AlAs superlattice. At certain electric field strengths anti-crossings of the fundamental transitions for heavy- and light-holes are observed, which can be assigned to resonant coupling of the electron wave functions over one, two and three superlattice periods. The lineshapes of the ER-spectra are discussed for a wide range of temperatures and field strengths