Properties of localized surface plasmon resonance in three-dimensional six-blade windmill nanostructure

The work aims to study plasmonics characters and optical chirality of three-dimensional (3D) six-blade windmill nanostructure. The 3D windmill nanostructure with adjustable lift-up angle was designed. The transmission, surface current distribution and magnetic field intensity were numerically analyzed by commercial FEM package (Comsol multiphysics) under the normally incident left-(LCP) and right-circularly polarized (RCP) light. To obtain the optical chirality of this 3D windmill nanostructure, asymmetry g-factor was calculated. Two distinct coupling LSPR (Localized Surface Plasmon Resonance) modes with wavelength of 925 nm and 985 nm were observed in the transmission. By increasing lift-up angle from 0° to 60°, internal and external modes exchanged the locations. When lift-up angle was equal to 45°, the 3D windmills showed much stronger optical activity, and the maximum asymmetry g-factor was of 0.6, showing best circular dichroism effect under different resonance modes. LSPR modes have strong dependence and regulation performance on geometrical parameters. The optical chirality is very sensitive to lift-up angle of windmill blade. The results can provide reference for designing novel chiral optical nanostructures, and may provide new ideas in applications of the interactions between photons and electrons. © 2019, Chongqing Wujiu Periodicals Press. All rights reserved.