Spectral resonant properties of reflected light for metal dielectric subwavelength gratings in visible regions

Abstract

A metal-dielectric grating consists of alternating metal and dielectric materials with period less than single wavelength of visible radiations. Optical behaviors of reflection spectra of this grating for s-polarized and p-polarized incident white light are studied systematically. For reflected light, it is the p-polarized light rather than s-polarization shows unusual optical behaviors with characteristics of single-peak spectra, higher peak efficiencies of higher than 75% and lower off-resonant efficiencies. The spectral width of p-polarized light with desirable frequency-selective functions is much wider. There exist two resonant areas for p-polarizations extending toward each other as filling factors increase, and positions of the resonances are mainly determined by grating periods existing linear relationships between them. For making positions of resonances occur in visible wavelengths, filling factors and grating periods should be respectively designed between 0.5 and 0.6 and between 0.25 and 0.45 µm. The newly observed properties of p-polarized lights can be used to exploit novel devices for reflection applications in the fields of optical securities and color filters.