4 January 2008 Electromagnetic transmission of T-shape periodic metallic grating
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Transmittance property of the metal film with periodic T-shape structure in the near infrared region has been investigated by using the two-dimensional Finite-Difference Time-Domain (FDTD) method. The T-shape means that the slits' width of the upper section is larger than the lower part in a cell. All slits are narrower than the illuminating wavelengths. The electromagnetic transmission peak waggles with wavelength increasing while augmenting the deepness of the upper section and fixing the total height of the grating film. The wider upper sub-wavelength slit displays larger waggle extent in the transmission spectrum. The sub-wavelength slits works as waveguide and effective indexes of the waveguide varied with the width of slits. The upper and lower sub-wavelength slits show different effective indexes due to they have different widths. Changing the deepness will adjust the length of the resonance cavity. The transmission spectrum waggles while deepening the upper slits, which is visible in Fabry-Perot resonance. The field distribution of the light with peak transmission in and near a cell of the grating testifies the Fabry-Perot effect. An analytical equation is also provided to approximately locate the transmission peaks. The T-shape structure in a cell of metal grating supplies a new way to modulate the transmission spectrum.
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Yanhua Wang, Yanhua Wang, Yan Zhang, Yan Zhang, } "Electromagnetic transmission of T-shape periodic metallic grating", Proc. SPIE 6837, Information Optics and Photonics Technologies II, 68371I (4 January 2008); doi: 10.1117/12.760051; https://doi.org/10.1117/12.760051

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