Color filter based on a two-dimensional submicrometer metal grating

A color filter incorporating a two-dimensional (2D) submicrometer metal grating is proposed. The device is designed by utilizing rigorous coupled-wave analysis (RCWA) and consists of four parts: a polymethyl methacrylate (PMMA) substrate, a dielectric film of high refractive index, a submicrometer grating, and a dielectric overlay of low refractive index. Its performance is enhanced effectively by applying a dielectric film of high refractive index. With a dielectric film height of 30 nm, a grating depth of 70 nm, and an overlay height of zero, three different devices are designed with the following structural parameters: a period of 420 nm for the red, a period of 350 nm for the green, and a period of 260 nm for the blue. For the red filter, the center wavelength is 645 nm and the peak transmission is 72%; for the green one, the center wavelength is 546 nm and the peak transmission is 75%; and for the blue one, the center wavelength is 455 nm and the peak transmission is 71%. The calculated result shows that its peak transmission efficiency increased more than 14% compared to the previous color filters incorporating a grating.