Tunable optical absorption of dimer nanostructure array achieved by angular evaporation

Dimer nanostructure as a pair of closely-spaced metal nanoparticles supports the localized surface plasmon (LSP) forming in designed area, showing signal enhancement and chirality, and it can offer a fundamental approach to studying the photonic interaction between nanoparticles. Thus an efficient way to realize dimer nanostructures with controllable gap size is important for the study of LSP resonance. In this paper, angle evaporation of Au is utilized to realize the varied dimer gap within tens of nm leading to the efficient adjusting of LSP resonance. Experimental results coupled with theoretical FDTD simulations revealed strong polarization-dependent transmission bands at the adjustable LSP resonance. The theoretical study showed an enhancement of over 2000 times of the localized electrical field intensity confined within dimer gap. Our method is expected to realize large-area LSP nanostructures for the application in metamaterial and chemical sensing.