Enhanced quality factors of surface lattice resonances in plasmonic arrays of nanoparticles

Key in the application of plasmonics is the realization of low loss or high quality (Q) factor resonances. Nanoparticle arrays are systems capable of sustaining remarkably high Q-factor resonances through the hybridization of plasmonic and photonic modes, known as surface lattice resonances (SLRs). SLRs result from the coupling of localized surface plasmon resonances (LSPRs) to in-plane orders of diffraction known as Rayleigh anomalies (RAs). To date, the highest Q-factors have been achieved with the (±1, 0) diffraction orders. However, these Q-factors are highly sensitive to the angle of excitation. Here, a strategy is presented to generate high Q-factor SLRs with low dispersion by coupling LSPRs to the (0, ±1) diffraction orders. 2D arrays of silver nanoparticles are investigated experimentally and numerically, and it is shown that the Q-factor of SLRs critically depends on the quality of the metal film, the detuning between RAs and LSPRs, and the absorption of adhesive layer used between the substrate and the metallic nanoparticles. These silver nanoparticle arrays can achieve Q-factors higher than 330 in the visible range. These extraordinarily high Q-factors could be increased to values above 1500 if no adhesive layer is used, which could significantly improve sensors and enhance nonlinearities in plasmonic systems.