Abstract

We report the first measurements of strong perpendicular field electroabsorption (quantum-confined Stark effect) in GaAs/AIGaAs quantum wells for light propagating parallel to the plane of the layer. The samples consisted of two quantum wells embedded in a GaAs/AIGaAs superlattice, clad with layers of GaAs to form a leaky waveguide. The superlattice was doped as a p-i-n diode, which was reverse biased to apply an electric field perpendicular to the quantum-well layers in the intrinsic region. For incident polarization parallel to the plane of the layers both the heavy hole (hh) and light hole (lh) excitons are seen in absorption. With perpendicular polarization, which is only accessible in the waveguide geometry, only the lh exciton appears. In both geometries the absorption edge shows a marked shift to lower energy with increasing field. In the perpendicular polarization the lh exciton is still resolvable at a field of 2.2 X 10⁵ V/ cm, at which point it has shifted by 40 meV. For a 150-µm long sample we obtain a modulation depth of 10 dB. We have also demonstrated for the first time optical bistability due to the self-electrooptic effect in a waveguide. The advantage of this geometry lies in the strong (20:1) on/off ratio obtainable. By using the appropriate biasing we have also demonstrated other self-electrooptic effects such as self-linearized modulation and optical level shifting similar to those previously demonstrated in MQWs at normal incidences. These effects have application to integrated optics and polarization sensitive devices.

© 1985 Optical Society of America