WAVEGUIDE AND MANUFACTURE THEREOF

PROBLEM TO BE SOLVED: To provide a waveguide for light beams, in which the inside face presents a specular surface and which can be easily lengthened, or a waveguide for radio waves, and their manufacturing method. SOLUTION: The waveguide is provided with an internal cylindrical body 11 made of γ-Al2 O3 or γ-Al2 O3 .H2 O, or a mixture of both the compounds, and an external cylindrical body 12 made of metals, etc., formed outside the internal cylindrical body. The manufacturing process of the waveguide contains a process in which -Al2 O3 or γ-Al2 O3 or γ-Al2 O3 .H2 O, or the layer 11 of the mixture of both the compounds is formed on the surface of a bar-like body made of aluminum or aluminum alloys, a process in which the external cylindrical body 12 is formed on the layer 11, and a process in which the internal cylindrical body 11 made of γ-Al2 O3 or γ-Al2 O3 .H2 O, or the mixture of both the compounds is formed by melting-removing aluminum or aluminum alloys in the bar-like body, on which the external cylindrical body 12 is formed, by means of Gallium solutions.