Waveguide-metal–dielectric bi-layer gratings for reflective filtering and color security

A multi-material structure composed of a linear polarizer and a dielectric sandwiched between two metal–dielectric gratings of with л phase shifts and embedded in dielectric is proposed. Its properties of reflection resonance together with filtering ability of visible light are discussed thoroughly and main factors of impacting its functions are identified. Both such properties and line-shapes of its spectra can be effectively trimmed by thickness, symmetry, period and metal material of two gratings. The behaviors of its single-peaks and peak-splits in spectra in combination with peak-shifts can generate uncommon color variation of interchanges in reflection based on structured coloration. Various color filters of reflection operating in visible light can be realized by it as well as intricate color effects arising from structures. This structure is valuable for applications of filtering, decoration and security.