MQW electroabsorption optical modulator performance enhancement using an artificial transmission line configuration

This paper compares the simulated modulation bandwidth and return-loss performance of InP multi-quantum-well (MQW) electroabsorption (EA) optical modulators using an artificial transmission line (ATL) structure with the corresponding performance obtained in a 50-Ω environment from a single EA device of the same total capacitance for the same modulating voltage. The comparison simulation includes the effects of loss at the modulation frequency in the EA devices and of the loss at the modulation frequency associated with the series inductors of the ATL fabricated on two alternative substrate configurations. The paper shows that with a three section ATL modulator, the 3-dB electrical bandwidth (3-dBe) improves by a factor of 2.3 without optimization of the ATL line parameters and by a factor of 3.4 with optimization. In addition, a much improved return-loss performance is obtained with the ATL configuration. The paper also illustrates the effect of EA device loss, ATL series inductor loss, and ATL group-delay variation on the modulation bandwidth.