Free-standing aluminium nanowire arrays for high-transmission plasmonic colour filters

Presented is a fabrication process for the transmission of red-green-blue (RGB) colour filters based on surface plasmons (SPs) using aluminium (Al) nanowire arrays patterned through electron-beam lithography and the lift-off technique. An array of Al nanowires was deployed over a through hole formed by sacrificial silicon etching. The period of the Al nanowire arrays is the dominant structural parameter in determining the transmission peak position of SPs for a given material configuration. The Al nanowire arrays are designed with the same Al wire width under the assumption of operation using a microelectromechanical systems (MEMS) comb-drive actuator for the realisation of an RGB tunable colour filter. The peak wavelength of the transmitted light was red-shifted by increasing the period of the Al nanowire arrays from 450 to 600 nm, and RGB colours were demonstrated. A black pixel was produced using the 400 nm pitch Al nanowire array. The maximum measured transmittance of the peak wavelength was 56%. In addition, the number of nanowires sufficient for low-power operation by a MEMS comb-drive actuator was investigated and sufficient transmission light intensity was obtained from the pixel size of 10 μm², including 20 Al nanowires.