Tunable optical transmission properties of Au/Al multilayer slit gratings

Abstract

We propose perforated Au/Al multilayer slit gratings and study their optical transmission properties. Results show that there is a relatively fixed transmission wavelength around 485 nm for the resonant peak of Type-1, and its intensity weakens, while more resonant peaks emerge for the peaks of Type-2 as the layer number N increases. It is also presented that the resonant transmission sensitively depends on the slit width and thickness of the metal Al film, magnitude modification, redshift and blueshift of the resonance modes, and bandgap are observed. A metallic heteromultilayer slit grating for a subwavelength band-stop filter in the range of visible light can be achieved. To understand its physical origin, a field-interference mechanism and Fabry–Pérot-like resonance theory have been suggested. In addition, it is found that, compared with the conventional single-Au-film slit grating, all resonant peaks exhibit a blueshift and the peak collapses first and is subsequently enhanced as the ratio of the Al metal increases. The proposed nanostructures and results may have great potential applications in subwavelength near-field optics.