M-Point Lasing in Hexagonal and Honeycomb Plasmonic Lattices
Xitlali G. Juarez, Ran Li, Jun Guan, Thaddeus Reese, Richard D. Schaller, Teri W. Odom
Abstract
This paper reports the observation of band-edge states at the high-symmetry M-point in the first Brillouin zone of hexagonal and honeycomb plasmonic nanoparticle (NP) lattices. The surface lattice resonance at the M-point (SLRM) of a hexagonal lattice results from asymmetric out-of-plane dipole coupling between NPs. In contrast to the hexagonal lattice, honeycomb lattices support two SLR modes at the M-point because of their non-Bravais nature: (1) a blue-shifted SLRM1 from the coupling of two distinct out-of-plane dipole LSP resonances, and (2) a red-shifted SLRM2 from in-plane dipole–dipole coupling. By incorporating organic dye solutions as gain media with Ag NP lattices, we achieved M-point lasing from both hexagonal and honeycomb lattices. Understanding coupling mechanisms at high-symmetry points in NP lattices with the same geometry but different unit cells is important to assess the prospects of topological states in plasmonic systems.