Strain-tunable plasmonic crystal using elevated nanodisks with polarization-dependent characteristics

This paper reports on the mechanical tuning of optical resonances of a flexible plasmonic crystal. The device is structured with a square lattice nanopost array standing out of an elastomer substrate and coated with a gold thin film. The gold nanodisks residing on top of the nanoposts support a surface plasmon polariton (SPP) Bloch wave mode at the gold-air interface. By applying a strain along a planar direction of the substrate, the period of the elevated nanodisk array changes, thus altering the SPP resonance wavelength. Because the applied strain breaks period symmetry of the nanodisk array, the original single resonance mode is split into two polarized resonance modes. For the incident light polarized parallel with and perpendicular to the direction of the applied strain, the corresponding resonance modes are shifted in opposite directions at a rate of 1.6 6 0.1 nm for every 1% change in strain. During stretching and compressing the substrate, the applied strains only change the period between nearby nanodisks without affecting their shape and morphology. This has improved reliability and repeatability of resonance tuning of the device. VC 2016 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4942454]