Design and simulation of metal-insulator-metal nanoresonators for color filter applications

Traditionally, liquid crystal display (LCD) systems employ color filters that are fabricated using organic dye and pigment based colorants. As a result, conventional color filters can lower the system performance by removing substantial amount of incident light through absorption. Also, the transmission bandwidth can be unacceptably large. Furthermore, there is a need to combine functions of multiple optical elements on one, facilitating miniaturization and compactness. Metal-insulator- metal (MIM) nanoresonators that can combine the functions of color filtering and polarizing can provide a useful solution to some of these issues. An MIM nanoresonator structure is proposed for use as color filters. However, the proposed structure uses high refractive index, inorganic materials in the insulator layer. Also, the bandwidth of transmission is not narrow enough to generate saturated color. Here, we simulated some MIM nanoresonator structures that might be realized using relatively low refractive index, polymeric materials and can function as polarizing, color filters in transmission mode. These structures might also yield narrower bandwidths of transmission. The simulations are carried out using a monochromatic version of RC-FDTD. This algorithm uses the 1st order Drude model to evaluate the convolution operation needed to make FDTD stable for metals for which the real part of permittivity is negative. Unlike the conventional RC-FDTD [3], the Drude parameters are computed at each wavelength of the incident light using the corresponding handbook value of permittivity. Hence, this version of RC-FDTD allows us to use the handbook permittivity values at all wavelengths of operation.