Using finite difference time domain techniques, the transmission of light through 6 μm period arrays of sub-wavelength holes in optically thick metallic films is investigated. Over the wavelength range 2 μm to 16 μm, it is observed that by centering an additional metallic element within the sub-wavelength hole, well defined resonance peaks are produced which arc strongly dependent on resonator and hole dimensions but only weakly dependent on metal film thickness. Resonant line-width however, is found to be strongly dependent on metal film thickness. Thicker films produced the narrowest full-width half-max values, which were less than 1.0 μm. Such control of resonant wavelength and line-width, along with the size of the elements investigated and the 6 μm array period used, suggests the fabrication of an optical filter with transmission properties that vary across the face of a focal plane array for use in multispectral imaging applications.
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