Topology Optimization Enables Freeform Matrix Fourier Optics

Yu-Tzu Liu^1*, Yun-Chien Wu¹, Yao-Wei Huang¹

¹Department of Photonics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan

* Presenter:Yu-Tzu Liu, email:a312514027.ee12@nycu.edu.tw

Polarization is a critical light property often omitted in traditional mathematics. Current metasurfaces can only measure one type of polarization at a time. Matrix Fourier optics enables simultaneous polarization-modulation at different diffraction orders within a single-layer metasurface. However, this approach via forward design still leads to efficiency losses. Our research uses topology optimization to design a freeform metasurface diffracting the six most common polarizations in Stokes parameter measurements into targeted diffraction orders, achieving polarization contrast up to 98% in numerical results and 99% in experimental results. The freeform metasurface offers significant flexibility with customizable functionalities and asymmetric design suitability, etc.

Keywords: metasurface, inverse design, topology optimization, adjoint method