Attenuation characteristics of a planar dielectric coated metallic waveguide for 10.6 μm radiation

Flexible planar aluminum waveguides coated with various thicknesses of dielectric layer (CaF ₂) have been realized for a 10.6 μm application. The coupling efficiency between a gaussian CO ₂ laser beam and the guides has been discussed: multimode or single mode excitation can be obtained depending on the value of the ratio η between the laser waist and guide width. Transmissions and attenuations of these guides have been measured confirming the theoretical tendency of a dielectric layer varying from 0 to an optical thickness of λ/4 to reduce TM mode losses while increasing TE mode losses.