Improvement in performance of traveling wave electroabsorption modulator with asymmetric intra-step-barrier coupled double strained quantum wells the active region, segmented transmission-line and mushroom-type waveguide

In this paper, asymmetric intra-step-barrier coupled double strained quantum wells structure (AICD-SQW), segmented transmission-line and mushroom-type waveguide that improve the performance of traveling wave electroabsorption modulators (TWEAM) are presented. The AICD-SQW structure shows that electroabsorption modulator properties such as large change in absorption, high extinction ratio, large Stark shift, very low insertion loss, zero chirp, and higher figures of merit are possible to be achieved simultaneously as compared with intra-step quantum well (IQW). The segmented transmission-line method allows us to design a TWEAM with above 25 Omega impedance and very high bandwidth. Furthermore, increasing the width of p-cladding layer with the same active layer to reduce the resistance in p-i-n mushroom-type waveguide of TWEAM based on AICD-SQW improve the microwave propagation loss and thus the high-speed electro-optical response. For this purpose, the transmission-line microwave properties of TWEAM such as microwave index, microwave loss, and characteristic impedance are obtained for active and passive segments of transmission-line. Then equivalent circuit model elements are extracted. The modulation response of segmented transmission-line mushroom-type TWEAM is obtained by HSPICE simulation and compared to circuit model simulation results of conventional mushroom-type TWEAM counterpart. The analysis results indicate that the segmented transmission-line mushroom-type TWEAM can achieve much wider bandwidth than the conventional mushroom-type TWEAM counterpart, with a small penalty in electro-optic conversion gain due to AICD-SQW structure.