Abstract
Silicon photonic modulators have strong nonlinear behavior in phase modulation
and frequency response, which needs to be carefully addressed when they are used in
high-capacity transmission systems. We demonstrate a comprehensive model for
depletion-mode Mach–Zehnder modulators (MZMs) on silicon-on-insulator, which provides a
bridge between device design and system performance optimization. Our methodology
involves physical models of p–n–junction phase-shifters and traveling-wave electrodes,
as well as circuit models for the dynamic microwave-light interactions and time-domain
analysis. Critical aspects in the transmission line design for high-frequency operation
are numerically studied for a case of p–n–junction loaded coplanar-strip electrode. The
dynamic interaction between light and microwave is simulated using a distributed circuit
model solved by the finite-difference time-domain method, allowing for accurate
prediction of both small-signal and large-signal responses. The validity of the model is
confirmed by the comparison with experimental results for a series push–pull MZM with a
6 mm phase shifter. The simulation shows excellent agreement with experiment for
high-speed operation up to 46 Gb/s. We show that this time-domain model can well predict
the impact of the nonlinear behavior on the large-signal response, in contrast to the
poor prediction from linear models in the frequency domain.
© 2016 IEEE
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