Fabrication of low-loss zinc-selenide coated silver hollow waveguides for CO₂ laser light

ZnSe coated Ag hollow waveguides transmitting CO₂ laser light were developed. An inner ZnSe coating of good quality was obtained with high rf power and high translating speed in deposition by rf sputtering. The inner ZnSe layer was found to be amorphous by x-ray diffraction analysis; A layer structure (ZnSe-Ag) was observed by Auger electron spectroscopy analysis. Transmission properties of the short waveguides with 25 cm length were evaluated by measurements of loss spectra in the mid-IR region. As a result, ZnSe coated Ag waveguides showed lower loss than the Ge coated one fabricated previously, and the loss for CO₂ laser light was predicted to be 0.021 dB/m. Furthermore, it was found that a ZnSe coated Ag waveguide is durable in practical use.