Transient analysis of a high-speed thermo-optic modulator integrated in an all-silicon waveguide

A combined thermal and optical simulation study is performed on an all-silicon waveguide integrated thermo-optic Fabry-Perot modulator to assess the impact of the driving signal shape on the device speed performances. The results clearly indicate that the cooling phase after pulse constitutes the true speed-limiting factor the application of a heat of a device, which is otherwise in thermal equilibrium with the environment. Therefore, to enhance the heat exchange in this phase, we analyze the hypothesis of applying a thermal bias and hold the modulator at a higher average temperature with respect to the environment and the substrate heat sink. With this approach, a new driving signal is proposed and predicted to allow a transmission rate of 2.2 Mb/s, representing over a 30-fold bandwidth widening with respect to the standard modulation scheme. We also discuss the fabrication process of this kind of modulator, reporting on its first prototypal realization and preliminary optical characterization.