A bilayer Al nanowire-grid polarizer integrated with an IR-cut filter

A bilayer Al nanowire-grid polarizer integrated with an IR-cut filter has been developed to exhibit high polarization sensitivity in a visible region. The IR-cut filter consisting of Ti3O5/SiO2 multilayer oxide film completely blocks the incoming light over 680 nm wavelength and shows high transmittance over 95% in the visible range. By incorporating the reversible nanostructures molding lithography and the two-step oblique angle deposition of the e-beam evaporator, we are able to secure the nanowire-grid patterning with 50-nm resolution in a form of bilayer Al grating. Then, it is found that the plasmonic coupling between the nearby Al layers leads to the high transmittance of TM-mode light passing through the IR-cut filter, while there is no plasmonic coupling between them for TE-mode case. Both the Finite-Difference Time-Domain simulation and experimental results show that the transmittance of the TM polarization for the grid height of 110 nm reaches up to 90% and the extinction ratio is around 300∶1 in the visible range. Therefore, the observed results can provide an insight in designing the bilayer Al based plasmonic polarizer combined with the IR-cut filter in order to achieve better performance utilizing the plasmonic coupling effect.