A liquid crystals modulated optical tunable filter based on Fano resonance of Au nanorod trimer

We theoretically studied the liquid crystals modulated optical tunable filter based on Fano resonance of Au nanorod trimer. Plasmonic nanorods can support Fano resonances, where the line shape characteristics are controlled by the geometry of nanorods. Here a polarization-dependent Au nanorod trimer was designed, where the three nanorods have the same geometric parameters and form a C-shape. When the plasmon modes of the longitudinal nanorod and the two transverse nanorods couple at resonance wavelength, a Fano resonance occurs. Due to liquid crystals can change the polarization direction of light, the transmission spectra of Au nanorod trimer can be switched on and off with different phases of liquid crystals when incident light passes through liquid crystals before reaching the Au nanorod trimer. Furthermore, filter optical characteristics are highly tunable by changing the thicknesses of Au nanorod trimer and its coating layer. Fano resonances show a large light extinction in periodic array of assembled nanorods, which can be used in optical tunable filter and optical switch.