The correlation between electrical properties and surface plasmonic properties on ITO films with diffraction grating

The correlation between electrical properties and surface plasmon resonance (SPR) wavelength was discussed using ITO grating coupler. ITO films were prepared on SiO $$_{2}$$ /Si substrate by RF sputtering with thermal annealing, and the grating was directly fabricated on the sample surface by focused ion beam. Electron density and mobility were evaluated by fitting optical reflection spectra according to Drude model, and then SPR wavelength was estimated from the dispersion relation of surface plasmon. Characteristic SPR dip was observed in polarized reflection spectrum, however, measured wavelength was different from theoretically estimated value. The discrepancy was explained by introducing the assumption based on effective medium theory, in which the grating is assumed as a thin film with effective refractive index.