Due to the tail of plasmon resonance in MIR wavelengths, transmission and reflection spectra varied with the disc diameter as shown in Figs. . Especially the smaller disc diameters reduces the transmission at visible wavelengths. On the other hand, the optical properties of ITO show the resonance wavelength shift towards the longer wavelengths. This is due to the fact that ITO has a larger real part of the refractive index. Therefore the effects of reduced extending to the visible wavelength region is smaller than that for the Au thin mirror MIM structures.