Flexible plasmonic lattices for polarization-selective and dual-parameter dynamic modulation of surface lattice...

Surface lattice resonances (SLRs) in plasmonic nanoparticle arrays provide narrow optical features that are sensitive to lattice periodicity and the surrounding refractive index. Although mechanical tuning, refractive-index modulation, and polarization-dependent SLR responses have each been investigated previously, comparative channel-resolved studies of how orthogonal SLR channels in the same flexible anisotropic lattice respond to these external perturbations remain limited. Here, we fabricate rectangular Au nanodisk lattices on flexible PDMS substrates and investigate their polarization-resolved transmittance spectra under uniaxial mechanical strain and liquid-superstrate refractive-index variation. Under x-axis stretching up to 5%, the y-polarized resonance redshifts from 1269 nm to approximately 1335 nm, whereas the x-polarized resonance blueshifts from 1167 nm to approximately 1141 nm. Under y-axis stretching, the x-polarized resonance redshifts from 1167 nm to approximately 1225 nm, while the y-polarized resonance blueshifts from 1269 nm to approximately 1247 nm. Increasing the liquid-superstrate refractive index from 1.39 to 1.49 redshifts the resonances, with fitted sensitivities of approximately 359 nm/RIU and 305 nm/RIU for the two channels. In addition to resonance shifts, the linewidths and quality factors exhibit channel-dependent evolution under strain, consistent with strain-dependent changes in radiative-loss suppression and spectral inhomogeneity. The distinct strain- and refractive-index-induced shifts expand the accessible tuning space and may support multi-parameter calibration. These results provide useful design insights for flexible SLR-based optical filters, refractive-index sensors, and reconfigurable nanophotonic devices.