  Color filters have important applications in the area of Nano-spectroscopy
and ccd imaging applications. Metallic nanostructures provide an efficient way
to design and engineer ultrathin color filters. These nanostructures have
capability to split the white light into fundamental colors and enable color
filters with ultrahigh resolution but their efficiency can be restricted due to
high losses in metals especially at the visible wavelengths. In this work, we
demonstrate Si nanoantennas based all-dielectric color filters, which are
sensitive to incident-wave polarization and, thus, tunable with the aid of
polarization angle variation. Two different information can be encoded in two
different polarization states in a single physical nanostructure. The
nanoantenna based pixels are highly efficient and can provide high quality of
colors due to low losses in dielectric at optical frequencies. We
experimentally demonstrate that a variety of colors can be achieved by changing
the physical size of the nonsymmetric cross-shaped nanoantennas. The proposed
devices cover an extended gamut of colors on CIE-1931 chromaticity diagram due
to the existence of high quality resonance in Si nanoantennas. The device shows
significant tunability of color while operating this color filter device in
transmission as well as in reflection mode.
