Topology Optimization

I have recently been interrested in optimizing the shape of microwave/photonic devices for various applications and control of electromagnetic waves.

Invisibility cloaking

I designed an all-dielectric cloaking device at microwave frequencies. A gradient based topology optimization is employed to find a dielectric permittivity distribution that minimizes the diffracted field in free space. The layout is binary, i.e. made either of standard ABS plastic or air and is designed to reduce the scattering from an ABS cylinder excited by a line source for TE polarization. We study the performances of cloaks optimized for one, two and three frequencies in terms of scattering reduction and correlations with respect to the free space propagation case. Finally, a modal analysis is carried out providing physical insights on the resonant cloaking mechanism at stake.

Related article

  • B. Vial, and Y. Hao, Topology optimized all-dielectric cloak: Design, performances and modal picture of the invisibility effect. Opt. Express 23 (18):23551, (2015) DOI | URL

Illusion device

We report the design, fabrication and experimental verification of an illusion device working at microwave frequencies. A two dimensional topology optimization procedure is employed to find the binary layout of a dielectric coating that, when wrapped around a metallic cylinder, mimics the scattering from a predefined, arbitrarily-shaped dielectric object. Fabrication is carried out with 3D-printing and spatially resolved near field measurements in a waveguide configuration were performed, allowing us to map the illusion effect. Our work provides general guidelines for engineering electromagnetic illusions but can be extended to shape the near and far-field radiations using low index isotropic materials.

Related article

  • B. Vial, M. Torrico, and Y. Hao, Optimized microwave illusion device. Sci Rep 7 (1):3929, (2017) DOI | URL