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

We explore the semi-analytical design strategies for indium phosphide (InP) based Mach- Zehnder modulators (MZMs), leveraging their superior electro-optic efficiency, lower intrinsic carrier concentration, and high thermal conductivity for high-bandwidth modulation. These modulators enable integrated photonics circuits with active and passive components on a single chip. High-performance, co-planar stripline MZMs on the generic InP platform have been shown allowing smaller device footprint and reduced microwave loss, maintaining high bandwidth and compatibility with generic foundry processes. We develop an analytical equivalent circuit model that facilitates swift extraction and optimisation of key performance metrics such as the electrical −6 𝑑𝐵 and
electro-optic -3 𝑑𝐵 bandwidths. This model is not only significantly more efficient than conventional finite element methods but also provides a physical intuition on the interrelationships between design parameters and enables wide-scale optimisation of the design geometry to produce bandwidths exceeding the current state-of-art (> 120 𝐺𝐻𝑧).