Control of chirp parameter in electroabsorption modulators by designing asymmetric triple coupled quantum well structure

The external modulator is a key device for long-haul, high-speed optical transmission systems. In such systems the product of the square of bit rate and the transmission length is limited by the modulator´s chirp parameter and the fiber dispersion; the optimum chirp parameters for conventional silica fiber and dispersion-shifted fiber are -1 and 0, respectively. However, most multiple-quantum-well electroabsorption modulators produce positive chirp parameter. In this paper, we theoretically show that the chirp parameter is controllable through well width of the asymmetric triple coupled quantum well.