Electro-Optical Ring Modulator: An Ultracompact Model for the Comparison and Optimization of p-n, p-i-n, and Capacitive Junction

Silicon photonics electro-optical ring modulators are key components in short-range optical interconnects, as they can be operated at low-voltage, compatible with CMOS circuit drivers. However, a full exploration of design tradeoffs is currently lacking. In this paper, a semianalytical simulation scheme is proposed for the optimization and comparison of different kinds of silicon ring modulator junction. We first describe the physical parameters used in the conventional models of active ring resonators, and apply the model to the case of carrier depletion in the well-known p-n junction. The same approach is applied to both p-i-n and capacitive junctions, and leads to a comparison of each type of modulation junction in which the strengths and weaknesses of each configuration are highlighted. We then propose a compact optimization model that directly provides the best opto-geometrical compromise between high modulation efficiency, low optical losses and large bandwidth.