Tunable Lattice Plasmon Resonances in 1D Nanogratings

Lattice plasmon resonances or surface lattice resonances (SLRs) supported in two-dimensional (2D) metal nanoparticle arrays have extremely narrow line widths and highly localized electric field enhancements, which are key properties for realizing plasmon lasers and hybrid solid-state lighting devices. This paper reports lattice plasmons in one-dimensional (1D) metal nanogratings with broadband tunability (over 400 nm) far beyond their 2D counterparts at visible wavelengths. The large wavelength tunabilities of 1D or line-SLRs are from the lower symmetry of the structures compared to 2D arrays based on nanoparticles. We demonstrate that line-SLRs exhibit a Fano-like character based on coupling between an out-of-plane plasmon excitation and 1D Bragg diffraction modes. We show how the height and periodicity of the grating determine the spectral properties of the line-SLRs. By adjusting the line height, we achieved high-quality lattice resonances, even in index-mismatched environments.