Electro-optic quantum well device

A semiconductor device for modifying optical transmission comprising:

• a substrate;
• a multilayered semiconductor quantum well structure located on said substrate and including a plurality of pairs of quantum well layers of mutually difference widths separated from each other by a respective semiconductor barrier layer;
• an outer capping layer on said semiconductor structure, said quantum well structure being located intermediate said substrate and capping layer thereby;
• means for applying an electric potential across said electric field across said quantum well structure which when applied generates an electric field across said quantum well layers and operates to bring the electron sub-band energies of said quantum well layers of different widths into and out of resonance, thereby allowing excitons in the wells to undergo resonant field ionization, wherein electrons tunnel back and forth between said wells causing an alteration of the coefficient of light absorption of wavelengths in the region of the excitonic absorption feature;
• and
• means for directing optical energy from and external source to said plurality of pairs of quantum layers substantially parallel to the interfaces between contiguous layers of said semiconductor structure whereby light transmitted through said structure will undergo a phase shift due to resonant field ionization of quantum confined excitons.