Enhancement of optical bandwidth using high barrier multiquantum well structures

We demonstrate the enhancement of optical bandwidth for modulators based on the quantum confined Stark effect using high barrier multiquantum well structures. This is achieved by carefully placing the Fabry-Perot mode in the wavelength region where the absorbing layer exhibits anomalous refractive index dispersion in the vicinity of the exciton peaks. The enhancement in both the exciton oscillator strength and the separation between the heavy hole and light hole in high barrier multiquantum well structures ultimately results in the enhancement of optical bandwidth. A simulation example shows an increase of 2.5 nm in optical bandwidth at the cost of a factor of three increase in electric field to obtain the same contrast ratio characteristics as a modulator fabricated with low barrier material.