We report the first measurements of linear and nonlinear absorption and perpendicular field electro-absorption (Quantum Confined Stark Effect) in GaAs/AlGaAs quantum wells for light propagating parallel to the plane of the layers. This geometry is well-suited for integrated optics. With increasing intensity the absorption is found to saturate at the very low intensity of 300 W/cm2. With increasing electric field the absorption edge shifts to longer wavelengths by as much as 40 meV, giving a modulation depth >10 db in a 150 μm long device. The strong dichroism present in this geometry is retained even at high fields, making polarization sensitive electro-optical devices possible. We also demonstrate in the waveguide geometry optical bistability due to the self-electro-optic effect with 20:1 on/off ratio.