Electro-optic and photorefractive properties of long-period Fibonacci superlattices

We have investigated the transverse-field electroabsorption of long-period GaAs/AlGaAs Fibonacci superlattices for three different realizations of the Fibonacci sequence and assessed their bandwidth in photorefractive four-wave mixing experiments, The one-electron density of states exhibits a wide fractal distribution of quasibands, suggesting the ability to tailor bandwidths for optical applications. Many-electron effects and the inter-well coupling shift the excitonic oscillator strength to the low-energy edge of the spectrum in all cases, producing a diffraction bandwidth that is relatively independent of coupling in both weak- and strong-coupling Fibonacci superlattices. (C) 1996 American Institute of Physics.