Novel modulator structure permitting synchronous band filling of multiple quantum wells and extremely large phase shifts

The authors 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 bandgap. The measured electrorefractive response shows that the maximum phase shift that can be achieved in one absorption length is one order of magnitude larger than 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. It is concluded that BRAQWETS provides a novel basis for high-performance electroabsorption modulators as well as low-loss phase modulators and interferometric amplitude modulators and switches. With suitable engineering, it will also be possible to construct multi-quantum-well lasers and detectors using BRAQWETS.<>