Design and simulation of a polarized color filter based on sub-wavelength metal gratings

A polarized color filter with good performance is proposed. This device consists of a transparent substrate, a bottom metal grating, a low refractive index dielectric layer, a high refractive index dielectric layer and a top metal grating. The bottom metal grating has a small period which is mainly for polarization, and the top metal grating with a large period is for color-filtering. The parameters that affect the transmission and polarization properties of the device have been simulated and analyzed by utilizing the finite-difference time-domain (FDTD) method. A polarized color filter having broadband peak, high transmission and high extinction ratio is designed. The peak wavelengths and the corresponding transmittances are as follows: 635nm and 78.7% for red, 541nm and 83.2% for green, 452nm and 82.4% for blue. Extinction ratio above 1000: 1 has been achieved within the full width at half maximum (FWHM) range for all the three colors. This device is suitable for liquid crystal displays.