Subtractive Color Filters Based on a Silicon-Aluminum Hybrid-Nanodisk Metasurface Enabling Enhanced Color Purity

Highly efficient subtractive tri-color filters of cyan, magenta, and yellow with enhanced color purity and robustness have been proposed and realized, by exploiting a silicon-aluminum (Si-Al) hybrid-nanodisk (ND) metasurface atop a Si substrate. The aspect ratio of the Si-Al hybrid ND is much lower than that of the conventional Si nanowire, which is disadvantageous due to its fragility and low color purity. In response to incident light impinging upon the metasurface, the hybrid-NDs individually play the role in exciting a magnetic dipole (MD) resonance through the mediation of Mie-scattering between the hybrid ND and air. The light stored in the resonance is coupled to the substrate, giving rise to a suppressed reflection. By virtue of the top Al ND, the excited MD resonance is strongly confined by the Si ND. As a consequence, a near-zero resonant dip that exhibits high off-resonance reflection and narrow bandwidth is produced for embodying highly efficient tri-color filters with enhanced color purity. The spectral position can be tuned by a simple adjustment of the hybrid-ND diameter. A full-color palette was successfully created with a high color purity and large color gamut. The proposed devices may be applied for photorealistic high-resolution color printing and holographic displays.