Robust inverse design of all-dielectric metasurface transmission-mode color filters

The strong dispersion, ultra-thin form-factor and robustness to degradation make metasurfaces attractive for color filter applications. In particular, transmission-mode filters using silicon could potentially replace conventional color filter arrays in backside-illuminated CMOS image sensors and enable novel multispectral image sensors. We report a robust inversedesign methodology using polygon-shaped, particle and void, meta-atoms. We predict that silicon metasurface transmission-mode primary color (RGB) filters designed with this approach exhibit enhanced color gamut, color purity and intra-pixel color uniformity in comparison to previous reports. The proposed robust inverse design procedure employs multi-island Differential Evolution whose fitness evaluation step uses a statistical model of nanofabrication imperfections. The statistical model can closely recreate the shape variations observed in micrographs of silicon metasurfaces fabricated using electron-beam lithography and is useful in guiding the optimization process towards robust designs.