Novel Mach-Zehnder polymer modulators using coplanar waveguide electrodes

Analysis, design, and experimental demonstration of polymer Mach-Zehnder modulators with novel In-plane coplanar waveguide (CPW) electrode are presented. Compared to conventional CPW electrode, the new In-plane CPW configuration significantly enhances the overlap integral between microwave and optical wave. The DC bias point which drifts in polymer modulators based on microstrip electrode is much stabilized in the new type of modulator. Furthermore the fact that CPW electrode has lower microwave loss at high frequencies than the microstrip enables CPW-based modulator to have wider modulation bandwidth. Polymer modulators consisting of optical Mach-Zehnder waveguides and Inplane CPW electrodes are designed and fabricated using CLD1/APC active polymer. For the modulators with 15, 18, and 21um gap spacing, the overlap and Vpi are tested and compared with theoretical calculations. Measurement results show that the push-pull Vpi of 9.5V and the r33 of 27pm/V are achieved with extinction ratio of more than 20dB. DC bias drift of modulators is tested for both microstrip and In-plane CPW electrodes and much stabilized bias is observed in modulator with In-plane CPW. The microwave S21 measurement shows the attenuation coefficient of 0.16dB/cm GHz for Mach-Zehnder modulator using In-plane CPW electrode, whereas 0.7dB/cm GHz for microstrip.