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cover_picture_mzi_modulator_small_zoom15This example has been updated. Find the latest version at Mach-Zehnder Modulator.






This example describes how to simulate the electro-optical behavior of a Mach-Zehnder interferometer (MZI) fabricated with a silicon-on-insulator (SOI) process using the multi-physics simulation environment of CHARGE. In particular, we will calculate the spatial carrier concentration as a function of applied voltage using the CHARGE solver. From the carrier concentration, we can estimate the device capacitance. The carrier concentration can also be exported to the FEEM solver where we can calculate how the optical properties of the waveguide change as a function of applied voltage.


The example will show to define the material properties,

2.the layout (geometry) of the device,

3.the addition of doping regions,

4.the definition of the simulation area,

5.the definition of electrical contacts, setting up a steady-state bias sweep,

6.meshing and simulation,

7.visualization and analysis of the results,

8.export electrical results for an FEEM simulation,

9.model index perturbation due to variations in charge density,

10.calculate field profiles and effective index of optical modes,

11.perform parameter sweep to calculate optical modes at different bias voltages, and

12.calculate phase shift and loss using post-simulation analysis.


A project file and script file are provided to assist with the application example. The project file contains the material properties, geometry, simulation region, solvers, and other simulation objects required to run the example. The script file contains the sequence of commands necessary to calculate the change in optical properties of the material that are required for an FEEM simulation.



FEEM (alternative option, FDE)

Associated files





In this topic:

Modeling instructions

Results and discussion


1. R. A. Soref and B. R. Bennett, SPIE Integr. Opt. Circuit Eng. 704, 32 (1987).


Lumerical products R2018b or newer



NOTE: To see the same example using the FDE solver in MODE for optical simulation, check out this archived KB page.


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