High-Q and Polarization-selective Resonances in Plasmonic Metasurfaces

Surface lattice resonances (SLRs) in periodic plasmonic nanostructure arrays arise from the coherent coupling between localized surface plasmon resonances and lattice diffraction modes, enabling sharp spectral features and enhanced optical responses. Here, we investigate the linear polarization–dependent SLR characteristics of a rectangular lattice composed of anisotropic gold nanobars. By selectively exciting the structure with orthogonally oriented linearly polarized light, we demonstrate pronounced polarization-selective excitation of distinct SLR modes. The results reveal that the coupling strength and spectral position of SLRs are strongly governed by the interplay between particle anisotropy and lattice periodicity along different crystallographic directions. Furthermore, the polarization-dependent response leads to significantly different resonance linewidths and field distributions, indicating controllable radiative damping and mode confinement. These findings provide a comprehensive understanding of polarization-selective SLR formation in anisotropic plasmonic lattices and offer a viable route toward the design of polarization-sensitive nanophotonic devices, including sensors, spectral filters, and tunable plasmonic components.