AlGaAs-GaAs quantum-well electrooptic phase modulator with disorder delineated optical confinement

Waveguide phase modulators, with 0.5- and 1-μm quantum-well (QW) active regions which are defined by impurity induced disordering are investigated theoretically. By controlling the extent of the interdiffusion in the lateral claddings, the refractive index difference between the core and claddings is used to provide single-mode operation. Strong optical confinement, which is required to produce single-mode high-efficiency modulation, requires the peak impurity concentration to be at the center of the QW active region. Moreover, the annealing time needs to be optimized so that single mode can be maintained at the desired bias field. A low dopant concentration is also expected to minimize the destruction of the modulator structure. The results show that since the core/cladding interface is graded, the width of the metal contact is important. A comparison of modulation efficiency for active layer thicknesses of 0.5 and 1.0 μm shows that the 0.5-μm one is a more efficient structure and its absorption loss can be reduced by increasing the applied field from 50 to 100 kV/cm