Four-Fold Color Filter Based on Plasmonic Phase Retarder

We present a plasmonic color filter based on periodic subwavelength silver nanowires, capable of changing the output color by simple rotation of a polarizer. The effect is enabled by a wavelength-dependent phase shift near the plasmon resonance, giving rise to a wavelength-dependent rotation of the incident polarization. Subsequent rotation of an analyzing polarizer leads to an output of four distinct colors (e.g., yellow, blue, purple, and red) and combinations thereof. The plasmon resonance itself can be tuned throughout the visible spectral region by proper choice of fabrication parameters.