PRODUCTION OF METALLIC PIPE

PURPOSE:To obtain an extremely smooth surface by coating the outside of an etchable metallic pipe with etchable polyimide resin. CONSTITUTION:The outside of an etchable metallic pipe, especially an Al pipe 5 is coated with etchable polyimide resin 6. A thin zinc selenide film 2 and a thin silver film 3 are uniformly formed on the outside of the polyimide resin 6 in succession by vacuum deposition, sputtering or ion plating. A sufficiently thick Ni layer 4 is then formed on the outside of the silver film 3 with the film 3 as an electrode. Finally the Al pipe 5 is removed by etching and the polyimide resin 6 is also removed by etching to obtain a hollow optical waveguide of silver lined with zinc selenide. The inner wall of the waveguide has a mirror finished surface.