Fig. 1. Structure of nanoparticles on grating. (a) Fabrication process of Au nanograting; (b) schematic diagram of BaTiO₃ nanoparticles loaded on Au nanograting

Fig. 2. Morphologies and optical properties of Au nanograting with different periodic constants. (a) Dark-field optical images and SEM images; (b) dark-field scattering spectra under TM-polarized incident light; (c) chromaticity diagram corresponding to dark-field sacttering under TM-polarized incident light

Fig. 3. Analysis on coupling mechanism of Au nanograting under incident light with different angles and polarizations. (a) Schematic diagram explaining Au nanograting scattering mechanism; (b) dark-field optical images under TM-polarized and TE-polarized incident lights, and illustration for the polarized state of incident light; (c) dark-field scattering spectra under TM-polarized and TE-polarized incident lights

Fig. 4. Morphologies and optical properties of Au nanograting with BaTiO₃ nanoparticles. (a) Dark-field optical images and SEM images; (b) dark-field scattering spectra under TE-polarized incident light; (c) dark-field scattering spectra under TM-polarized incident light; (d) chromaticity diagram of scattering spectra for BaTiO₃ nanoparticles

Fig. 5. Scattering spectra and mode analysis. (a) Experimental scattering spectra and (b) corresponding simulated scattering spectra of Au nanograting with or without BaTiO₃ nanoparticles under TE-polarized and TM-polarized incident lights; (c) schematic diagram for the oblique incident light in experiment and simulation; (d) simulated scattering spectra of Au nanograting with BaTiO₃ nanoparticles at different sizes under TE-polarized and TM-polarized incident lights

Fig. 6. Mechanism of optical mode coupling and simulated cross-sectional electric near-field distributions. (a) Schematic diagram explaining the optical mode coupling mechanism; (b) simulated cross-sectional electric near-field distributions of Au nanograting at resonant wavelengths; (c) simulated cross-sectional electric near-field distributions of Au nanograting with BaTiO₃ nanoparticles at wavelengths corresponding to the LSPR modes