How do I set an inverse design problem?

Date	Category
2023-12-21 19:01:14	Inverse Design

With Tidy3D’s integration with Autograd, setting up an inverse design workflow is straightforward.

All you need to do is define a function to create the Simulation object as a function of the optimization parameters, run the simulation, post-process the data, and return the cost function. Once this function is defined, you can call autograd.value_and_grad to run the simulation and obtain the gradients.

General Workflow

1. Create a make_sim function
   This function takes in the optimization parameters and returns a Simulation object.

2. Define a post-processing function
   This function calculates the objective (cost) function from the resulting SimulationData object.

3. Wrap it all in a single function
   This wrapper receives the optimization parameters, creates and runs the simulation, applies the post-processing, and returns the objective function.

4. Use autograd.value_and_grad
   Input the wrapper function into autograd.value_and_grad to obtain both the cost function value and its derivatives. These gradients can then be used in a gradient-based optimization algorithm to guide the inverse design process.

We highly recommend watching the Inverse Design lectures if you’re new to the adjoint method. You can also explore this tutorial for an introduction to automatic differentiation and adjoint optimization.