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MaxwellNet: Physics-driven deep neural network training based on Maxwell's equations

Joowon Lim, Demetri Psaltis

arXiv:2107.06164v1physics.optics

TL;DR

Computational electromagnetic simulations are time-consuming, while DNN approaches commonly require paired datasets generated by conventional solvers. The paper trains MaxwellNet using Maxwell-equation residuals instead, predicts fields for multiple aspheric microlenses, and combines it with DeepSDF for inverse design. The demonstrated scheme produces fields consistent with ground truth and designs a microlens that maximizes intensity at a target position.

  • Problem

    Existing DNN approaches typically require extensive paired input-output datasets generated by computationally demanding electromagnetic solvers.

  • Method

    MaxwellNet is trained with the residual of Maxwell’s equations as a physics-driven loss to predict electric fields from material-property distributions, then combined with DeepSDF for latent-space lens-shape optimization.

  • Results

    The network found electric-field distributions for various aspheric microlenses without target solutions, with results showing consistency with ground truth solutions.

  • Takeaways & Limitations

    Combining MaxwellNet and DeepSDF enabled inverse design of a microlens that maximizes light intensity at a target position.

  • Takeaways & Limitations

    The demonstrated scheme was limited to microlenses, and the final lens design was validated using COMSOL.

Abstract

from arXiv · show

Maxwell's equations govern light propagation and its interaction with matter. Therefore, the solution of Maxwell's equations using computational electromagnetic simulations plays a critical role in understanding light-matter interaction and designing optical elements. Such simulations are often time-consuming and recent activities have been described to replace or supplement them with trained deep neural networks (DNNs). Such DNNs typically require extensive, computationally demanding simulations using conventional electromagnetic solvers to compose the training dataset. In this paper, we present a novel scheme to train a DNN that solves Maxwell's equations speedily and accurately without relying on other computational electromagnetic solvers. Our approach is to train a DNN using the residual of Maxwell's equations as the physics-driven loss function for a network that finds the electric field given the spatial distribution of the material property. We demonstrate it by training a single network that simultaneously finds multiple solutions of various aspheric micro-lenses. Furthermore, we exploit the speed of this network in a novel inverse design scheme to design a micro-lens that maximizes a desired merit function. We believe that our approach opens up a novel way for light simulation and optical design of photonics devices.

MATERIALS AND METHODS

The study discretized MaxwellNet’s physics-driven loss on a Yee grid and trained the networks with specified optical, computational, and optimization settings. Inverse-design evaluations compared MaxwellNet outputs with COMSOL simulations.

  • MaxwellNet training discretized the physics-driven loss on the Yee grid using 50 nm spatial resolution.
  • Implementation: The networks were implemented in PyTorch and trained on an NVIDIA V100 GPU, while subsequent computations used a desktop computer with a GeForce GTX 1070 GPU.
  • The simulations used relative refractive indices of 1.53 for the material and 1.0 for the background at wavelength λ = 1 μm.
  • Symmetry reduced the x-axis pixel count and computational domain by half, with grids containing 320 and 192 pixels along x and z before reduction.
  • Inverse design: During inverse design, MaxwellNet and DeepSDF parameters remained fixed while only the latent vector was optimized with Adam for 200 iterations.The latent vector with the maximal figure of merit was retained as the final design.
  • Validation: COMSOL Multiphysics 5.4 performed full-wave 2D simulations with perfectly matched layers, and sampled outputs were directly compared with MaxwellNet fields.

CONTRIBUTIONS

J.L. carried out the modeling and computations, while D.P. supervised the project. All authors contributed to discussion and manuscript writing.

  • J.L. carried out the modeling and computations.
  • D.P. supervised the project.
  • All authors contributed to discussion and wrote the manuscript.
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