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We present detailed theoretical estimates of the optical properties of InGaAsP quantum well (QW) electroabsorption modulators (EAMs) operating at ~1550 nm wavelength. Absorption coefficients of QWs are obtained from the linear optical susceptibility. Exciton states 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-QWs are also included. Extending the study further to asymmetric double QWs (ADQWs) suggests that the small-signal modulation efficiency can be enhanced significantly at substantially lower operating bias voltage. Simple optimization of ADQW band structure results in a maximum slope efficiency ~3.8 times larger than that of SQW EAMs at a reduced operating bias field of 34 kV/cm compared with ~70 kV/cm for comparable SQWs.
Date of Publication: Sept. 2007