Differential transmission measurements on low-temperature-grown GaAs transmission lines with spatially separated pump and probe beams

Summary form only given. We report on differential transmission measurements in the presence of an electric in low temperature (LT) GaAs. The fields are applied via transmission line contacts. If pump and probe beams are focused on the same spot between the metal stripes, two different effects contribute to the differential transmission spectra (DTS); whereas the absorption of the probe beam is always decreased due to state filling caused by the intense pump beam, electroabsorption changes due to alteration of the internal field (Franz-Keldysh effect) can be positive or negative depending on the wavelength.