Novel Modulator Structure Permitting Synchronous Band Filling of Multiple Quantum Wells and Extremely Large Phase Shifts.

We have demonstrated synchronous band filling of multiple quantum wells using a novel "Blockaded Reservoir And Quantum Well Electron Transfer Structure" (BRAQWETS). The resulting electroabsorptive response per quantum well is not only stronger than that produced by the quantum confined Stark effect (QCSE) but is also free of induced absorption below the band gap. The measured electrorefractive response shows that the maximum phase shift that can be achieved in one absorption length is one order of magnitude larger that what is possible with QCSE. Furthermore, the dependence of induced refractive index change on the applied voltage is essentially linear. Design criteria for very high performance modulators with picosecond intrinsic speed are also discussed.