Abstract
The reflectance spectra from four proposed slit arrays were numerically and experimentally investigated. Lamellae of arrays consist of 0.1-?m-thick Au and 0.01-?m-thick Ti, which are on a smooth 508-um-thick Si substrate. Their profiles form three arrays of simple slits, which can synthesize the fourth, an array containing complex slits. Periods of the complex slit array and other three are 12, 3, 4, and 12 ?m, respectively. The incidence covered a broad-band mid-infrared (2.5 ?m-25 ?m) and it was illuminated on the other side of substrate. The specular reflectance at oblique incidence (theta = 30o) was measured with a Fourier-transform infrared spectrometer and numerically obtained using the rigorous coupled-wave analysis. Impacts of the semi-transparent Si window on reflectance spectra were analyzed. Unique features in spectra were elucidated considering the profile complexity. The validity of effective medium theory (EMT) was examined for each linearly polarized incidence. The expansion of EMT applicable region map will be attempted; moreover, results here will benefit the development of wavelength-selective and polarization-sensitive devices.