Nearly chirp-free electroabsorption modulation using InGaAs-InGaAlAs-InAlAs coupled quantum wells

We present an electroabsorption modulator based on slightly asymmetric InGaAs-InGaAlAs-InAlAs coupled quantum wells operated in the normally-off mode. The device exhibits a large change of the absorption coefficient in the vicinity of the zero-bias exciton peak wavelength with a very small change of the refractive index. The maximum excursion of the chirp parameter over the entire span of the bias voltage is less than +/- 0.1 for a specific wavelength or +/- 0.4 over an approximately 12 to 14-nm range. This structure is promising for low-chirp, high bit-rate electroabsorption modulators.