Misalign-dependent double plasmon modes “switch” of gold triangular nanoplate dimers

Abstract

The optical properties of the edge-to-edge gold triangular nanoplate dimers have been studied in theory by discrete dipole approximation method. Two clearly separated plasmon modes (low-energy and high-energy modes) are observed. Each of the double plasmon modes could be selectively turned on or off by modulating the misalign value of the dimer. When the misalign is <60 nm, the low-energy mode plays the dominant role in the spectra. In this case, the electric field intensities at the tips along the polarization direction fade down, whereas the intense electric field in the gap gets more concentrative, as the misalign increases. However, as the misalign is increased to 100 nm, the high-energy mode dominates the spectrum. And the intense electric fields concentrated around the outer tips become stronger as the misalign increases. The “switch” process is also accompanied by the inversion of the field vectors in the gap. In addition, the wavelength separation and positions of the double plasmon modes could be tuned flexibly by adjusting the gap value and the thickness of the dimer, respectively. These findings are promising for the nanophotonic switch, nanomotor, molecular ruler, surface enhanced fluorescence, surface enhanced Raman scattering, dual channel biosensor, and molecular imaging applications.