Optical filters consisting of metallic waveguide arrays
We demonstrate high-pass optical filters with cutoffs in the 0.3-10-micron spectral region. These filters consist of uniform arrays of hollow metallic waveguides, obtained by coating wafers of the previously developed channel-glass (CG) materials with a thin metal film. In these filters the channel diameter controls the cutoff frequency, the channel length controls the sharpness of the cutoff, and the channel density determines the transmission efficiency at cutoff. All of these parameters can be controlled in the CG starting material. The properties of the metal coatings that influence the filter properties are also discussed. Cutoff wavelengths near 300 nm have been achieved to date by using CG materials with submicrometer channel diameters. At all channel diameters, the transmission spectra include a peak just above the cutoff wavelength, where the transmission value can exceed that expected on the basis of the geometrical open area of the CG structure.
US Naval Research Laboratory, Washington, DC 20375, USA. armand.rosenberg@nrl.navy.mil
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Rosenberg
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Bolden