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Broadband wide-view all-dielectric handedness-preserving mirror

We report the theoretical design and experimental realization of a wideband, all-dielectric mirror that preserves the handedness of incident light upon reflection in the near-infrared range. The mirror consists of a high-contrast, near-subwavelength, one-dimensional dielectric grating on a Bragg mirror. We optimized this structure using a genetic algorithm and demonstrated its robustness against geometric imperfections and oblique incidence. Experimental reflection spectra measured under normal incidence in a circular polarization basis demonstrate a more than 100-nm-wide reflection band in which more than 98% of the reflected light preserves its handedness. The total reflection coefficient reached 80%. Furthermore, we demonstrate that the fabricated mirror maintains high performance even under oblique incidence for angles up to $\pm 15^\circ$. Owing to these unique characteristics, this mirror can serve as a reflective phase plate, making it an excellent candidate for the creation of a Fabry-Pérot resonator for chiral light.