Generalized blockaded reservoir and quantum-well electron-transfer structures (BRAQWETS) - Modeling and design considerations for high performance waveguide phase modulators

By deriving an equivalent circuit incorporating quantum capacitance and the concept of transcapacitance the interrelations among several figures of merit and the maximum intrinsic speed and their dependence on various design parameters have been elucidated for waveguide phase modulators based on the band-filling effect in the form of the recently demonstrated prototype blockaded reservoir and quantum well electron transfer structure (BRAQWETS). In addition, the performance potential of various BRAQWETS layer designs, which have been generalized to allow up to four quantum wells per basic period as well as a novel three-terminal symmetric device configuration, have been compared quantitatively by numerical simulation. Design guidelines for maximizing the performance of BRAQWETS waveguide phase modulators while taking into account of various constraints imposed by requirements on drive voltage, bandwidth, compactness, power dissipation, and single modedness of the waveguide are given. It is shown that, for equal amount of residual intensity modulation per pi phase shift, BRAQWETS can provide the best combination of low drive voltage, high speed, good phase-shift linearity, and low background absorption among the currently known phase-modulator structures.