Polarization angle affects energy of plasmonic features in Fano resonant regular lattices

Plasmonic nanoparticles in ordered lattices exhibit spectral features supported by Fano resonant coupling between dipole and/or quadrupole oscillations and constructively interfering diffracted modes. This work showed that the angle at which incident resonant irradiation was polarized relative to the axes of a rectangular 655 × 649 nm² lattice of 264 nm diameter gold nanospheres predictably modulated the energy of plasmonic spectral features. Measured peak wavelengths varied sinusoidally as polarization angle was rotated 360°. Quadrupole and dipole lattice resonance oscillations were phase shifted by 90°, consistent with theory. Experimental wavelengths were within 12 nanometers (1.8%) of wavelengths simulated for the lattice using a coupled dipole/quadrupole approximation.