Electrooptic properties of InGaAsP-based asymmetric double quantum well electroabsorption modulators

Theoretical calculations of the optical properties of InGaAsP quantum well (QW) electroabsorption modulators (EAM's) operating at c-band (similar to 1550 nm wavelength) is presented. Absorption coefficients of QW's are obtained from the linear optical susceptibility. Excitons are calculated in momentum space, which includes valence-band mixing, mixing of excitons originating in different subband pairs, and exciton spin-related optical selection rules. Various line-broadening mechanisms relevant to InGaAsP-QW's are also included. Investigations on asymmetric double QW's (ADQW's) show that the small-signal modulation efficiency, which is an important figure of merit for analog application, can be enhanced significantly at substantially reduced operating bias voltage. Simple optimization of ADQW band structure results in a maximum slope efficiency similar to 3.8 times larger than that of SQW EAM's at a reduced operating bias field of 34 kV/cm compared with similar to 70 kV/cm for comparable SQW's.