Base simulation

The base simulation defines the FDTD simulation that is used for optimization. In lumopt2, you can define the base simulation using an existing Lumerical FDTD .fsp project file, a Lumerical script file that sets up the simulation, or a Python callable that sets up the simulation.

Setting up the base simulation

The base simulation contains sources, monitors, and geometries necessary for the optimization.

Note

You don’t need to set up the optimization region in the base simulation, as this is separately defined in Python and passed into the parametrization.

To run optimization using lumopt2, the base simulation needs specific objects to capture the simulation results for the figure of merit. See the figure of merit article for more details.

For a general parametric optimization that directly maps optimization parameters to object properties, include the source, field region monitor, and objects whose properties are being optimized in the base simulation.

For parametric optimization using the ClosedCurve class, typically used in photonic integrated circuit applications, include only the ports and any input and output waveguides. The optimizable section is set up separately during parametrization.

Tip

If your figure of merit depends on multiple different base simulation setup, you can use the ProjectConfig object, along with the config argument when defining simulation results. See the figure of merit article for more details.

To set up the base simulation, you can use the Lumerical FDTD GUI, Lumerical scripting, or Python with PyLumerical.

The simple metalens example provides a sample FDTD project file for setting up a base simulation for a general parametric optimization case. The L-bend example provides an example of setting up the base simulation for a photonic integrated circuit application using PyLumerical.

For further information on setting up the base simulation, see the following resources:

• FDTD Product Reference Manual

• Lumerical scripting language index

• Simulation automation section of the user guide

Passing base simulation

The base simulation is passed into the optimization workflow through the Project object, as the Project.setup attribute.

To pass a base simulation that is either a FDTD project or a Lumerical script, provide the file path as a string. For further information on the parametrization, figure of merit, FDTD session, and runner, see the corresponding sections in the user guide.

project = lmpt.Project(setup = os.path.join(cwd_path, 'my_fdtd_project.fsp'), parametrization = parametrization, fom = fom,
                    fdtd_session = fdtd_session, runner = runner)

project = lmpt.Project(setup = os.path.join(cwd_path, 'setup_my_fdtd_project.lsf'), parametrization = parametrization, fom = fom,
                    fdtd_session = fdtd_session, runner = runner)

To pass a base simulation that is defined through a Python function, provide the function handle.

from my_setup_module import my_setup_function

project = lmpt.Project(setup = my_setup_function, parametrization = parametrization, fom = fom,
                    fdtd_session = fdtd_session, runner = runner)