Large refractive index changes in tunable-electron-density InGaAs/InAlAs quantum wells

The authors present measurements of electrorefraction and electroabsorption in a novel multiple quantum well waveguide structure in which each InGaAs quantum well is provided with an individual electron reservoir. External bias transfers electrons into the wells, thus quenching the absorption and producing a refractive index change at wavelengths below the bandedge which is linear in the applied voltage. The authors demonstrate that in this type of structure both the change in refractive index per applied field and the ratio of optical phase to intensity modulation can be significantly enhanced over those found in the quantum confined Stark effect