Equivalent circuit modelling of coplanar waveguide InP electro-optic phase modulators

Wider bandwidth, energy-efficient Mach-Zehnder modulators are required to meet ever-increasing performance requirements in fibre-optic communications. To push beyond the state-of-the-art device performance, better tools for design optimisation are highly warranted. Currently, the most accurate simulation tools are either formed empirically or are computationally intensive, limiting opportunities for extended design space exploration. In this work, we investigate utilising a parametric and analytical traveling-wave model for the design of Mach-Zehnder modulators in coplanar waveguide geometry. Vitally, the model incorporates both optical and electrical mechanisms and emerges from physical parameters such as layer thicknesses, materials properties, mask feature dimensions, and bias voltage. Evaluating the design from such parameters allows for holistic analyses of the design, elucidating the key tuneable parameters for improved performance. This is demonstrated utilising a factor of 3000 less computational time than traditional, finite element method, techniques to investigate the small-signal modulation bandwidth of the Mach-Zehnder modulators for an indicative set of 25 distinct parameters with varied mask design feature, epitaxy growth control, and load impedance.