Electro-optic modulators, which encode an electrical signal on an optical carrier, have been the subject of a lot of interest, and especially so in the field of silicon photonics where on-chip light sources are not readily available and direct modulation of the source is often not practical. A variety of modulator designs have been proposed to try and overcome design requirements imposed by physical device size, power consumption, modulation depth and bandwidth - including the Mach Zehnder interferometer, and modulator devices employing electro-absorption or resonant structures. As the performance requirements of these active components becomes more demanding, analysis and optimization of the modulator becomes a critical design task. Both optical and electrical simulations of modulators are necessary to fully characterize the device performance in silicon photonics systems.
The CHARGE sover can be used to analyze the electrical characteristics of the modulators by defining the component geometry and doping profile and to simulate the distribution of charge in the component in response to an applied voltage. Lumerical’s optical solvers (FEEM, MODE or FDTD) can then be used to perform optical simulations of the guided-wave structures and extract the modulation response such as phase and loss as a function of the applied voltage. Together, these products can be used to calculate modulation depth, Vpi, and extinction ratios.
Lumerical's multi-physics simulation suite DEVICE allows complete electo-optic simulation of modulators within a single unified design environment. The simulation workflow starts with the CHARGE solver which provides charge or electric field profile as a function of applied bias. This variation can be converted into index perturbation in the waveguide using appropriate model and can be used in the FEEM solver to simulate the optical response.
The optical simulation can also be done using Lumerical's other optical simulation tools such as FDTD or MODE.
•Build a 3D model of your modulator design. Geometric data can be imported from a STL or GDSII mask file
•Incorporate process data including impurity concentration profiles into your design, either by using the built in analytic profiles or importing from other process simulation tools
•Accurately model electronic transport in semiconductors using predefined material models, or customizing parametric models for mobility, surface and bulk recombination
•Simulate the current-voltage (IV) relationships and spatial charge distribution under steady-state or transient conditions
•Calculate the local, spatially varying change in optical material properties through the electro-optic effect and export that data for optical mode and propagation analysis in FEEM, MODE or FDTD.
•Extract AC device characteristics via small signal and transient analysis
•Solve for optical mode profiles in waveguides, accounting for spatially-varying optical material properties imported from CHARGE
•Calculate the effective index and loss as a function of applied voltage for modes in a tunable waveguide
•Propagate light through devices such as waveguide-based Mach Zehnder interferometers or ring resonators, including tunable waveguide sections
•Compute DC transfer functions and extract parameters such as Vpi and the extinction coefficient via the powerful matrix based scripting environment