GaAs/AlAs quantum wells for electro-absorption modulators

The authors demonstrate both theoretically and experimentally that the quantum-confined Stark effect leads to larger absorption changes in GaAs/AlAs quantum wells compared to the conventional GaAs/AlGaAs material due to the higher Gamma confinement. The lower indirect valleys in the AlAs do not degrade the performance, and the exciton resonance is maintained at higher energy shifts. The improvement in exciton oscillator strength is 14% at zero bias and nearly 50% at 70-meV shift. The larger exciton strength at high fields has important applications for optical modulators and switches that operate at the long-wavelength side of the zero bias exciton.