Low loss metallic waveguide for transmission of optical radiation

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Abstract
It is shown that a significant reduction of losses for transmission of optical radiation in a hollow metallic waveguide can be achieved by a proper dielectric coating of its walls. We solve and discuss the mode structure of a rectangular waveguide with two coated walls. An estimation of the losses in the metal walls and the dielectric coating is given. For short wavelengths (λ<10 μ) losses occur mainly in the metal wall, while for longer waveguide length they occur mainly in the dielectric. An example shows that for λ=1 μ the losses are reduced from 53 db/m for an uncoated waveguide to 4×10−6 db/m for a coated one.