RESUMO
The in-plane scattering patterns from a complex dielectric grating were both numerically and experimentally studied in contrast to those from well-known metallic gratings. The incidence was the transverse electric or transverse magnetic wave of wavelength λ=660 nm. The grating profile was complex with a period Λ=7.0 µm, while the material was lightly doped crystalline silicon. Patterns of the electric field, magnetic field, and spatial intensity distribution were demonstrated at the normal (θ(i)=0°) and oblique (θ(i)=+30°) incidence. Electric and magnetic fields were presented in the near field as well as the far field. The measured power ratio within -90°≤θ(r)≤+90° was plotted. Their major peaks and the numerically obtained diffraction efficiency of 21 orders (-10≤m≤+10 or -15≤m≤+5) of diffracted waves occurred at the same θ(r). Other peaks and stair-like shoulders of major peaks also exhibited in spectra.
RESUMO
Triple mechanisms were employed to trap mid-infrared (mid-IR) rays within a semi-transparent SiO(2) film sandwiched between gold gratings and a gold substrate. Dimensions of four absorbers were explicitly determined using an LC (inductor-capacitor) circuit model considering the role transition of SiO(2) film. The film behaves as a capacitance and an inductance when the real part of relative electric permittivity for SiO(2) is positive and negative, respectively. At the normal incidence of transverse magnetic waves, every absorptance spectrum of absorbers showed a peak at wavelength λ = 10 µm due to the first mode excitation of magnetic polaritons (MP). At oblique incidence, the Berreman mode led to another peak at λ = 8 µm while its bandwidth was expanded with epsilon near zero mode excited by diffracted waves. The full-width-at-half-maximum of both peaks exceeded 0.6 µm thanks to the SiO(2) loss. Other minor absorptance peaks in the mid-IR were caused by variants of the same MP mode.