NOVELTY - The plasmonic optical spectrum filtering device (220) comprises a resonator structure comprising a first electrically conductive metal grating structure and a dielectric material (232). The first electrically conductive metal grating structure comprises openings capable of transmitting a portion of an electromagnetic spectrum to generate a filtered output having a predetermined range of wavelengths via optical resonance. The resonator structure further comprises a second electrically conductive metal element disposed along an opposite side of the dielectric material, and a buffer material.    USE - The plasmonic optical spectrum filtering device is useful in a display device including a display screen (claimed) and as a color filter, where the display device includes LCD, liquid crystal on silicon projection display and eye-wear display and useful in electronic books and cell phones.    ADVANTAGE - The plasmonic optical spectrum filtering device can be economically and easily manufactured with reduced size and high peak transmission, and enhances transmission efficiency and energy efficiency of and provides low power consumption and slim dimension to the display device.    DETAILED DESCRIPTION - The plasmonic optical spectrum filtering device (220) comprises a resonator structure comprising a first electrically conductive metal grating structure and a dielectric material (232). The first electrically conductive metal grating structure comprises openings capable of transmitting a portion of an electromagnetic spectrum to generate a filtered output having a predetermined range of wavelengths via optical resonance. The resonator structure further comprises a second electrically conductive metal element disposed along an opposite side of the dielectric material, and a buffer material placed adjacent to the first grating structure. The second electrically conductive metal element is a second electrically conductive metal grating structure. The first electrically conductive metal grating structure, the dielectric material and the second electrically conductive metal grating structure together define the openings through the resonator structure that generates the filtered output having the predetermined range of wavelengths. The resonator structure serves as a polarizer device. The conductive metal structures serve as electrode to tune an orientation of liquid crystals. The first electrically conductive metal grating structure is a subwavelenth grating structure. The openings in the electrically conductive metal grating structure have dimension that is less than the predetermined range of wavelengths. A periodicity defined by the openings of the electrically conductive grating structure determines the predetermined range of wavelengths that is transmitted in a transmission-type filtering device or reflected in a reflection type filtering device. The predetermined range of wavelengths of the filtered output is in the visible light range, and has a color consisting of cyan, yellow, magenta, red, green and/or blue. INDEPENDENT CLAIMS are included for:    (1) a display device;    (2) a method of plasmonic optical spectrum filtering; and    (3) a method of making plasmonic optical spectrum filtering device.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic sectional view of a plasmonic resonator filtering device.    Filtering device (220)    Substrate (222)    Conductive metal material (228)    First metal grating layer (230)    Dielectric material (232)    Vertical microstructure. (248)