Abstract: A solution of a metallic compound or a cyclic olefin polymer is introduced into a metallic pipe to deposit the solution onto the whole inner wall of the metallic pipe followed by heat treatment at a high temperature to dry and solidify the solution, thereby forming a dielectric layer. Thus, a metallic hollow waveguide is prepared which comprises a metallic pipe, a dielectric layer provided on the inner wall of the pipe, and a hollow region defined by the inner wall of the dielectric layer. The above constitution makes it possible to provide a highly reliable hollow waveguide which is usable in a broad waveband, for which a quartz optical fiber is unusable, causes no significant transmission loss, can be mass produced, and can be easily produced in a reduced diameter and in an increased length, and to provide a method of making the same.

Abstract: A polyimide resin layer is formed on an inner surface of a metal pipe or a non-metallic pipe having a metal thin film on an inner surface to provide an optical hollow waveguide. The polyimide resin layer is transparent relative to a wavelength band of a laser light transmitted through the optical hollow waveguide. The optical hollow waveguide is fabricated by supplying solution of polyimide precursor to a hollow internal of the metal pipe or the non-metallic pipe, and heating and drying the solution to provide a polyimide resin layer. The solution-supplying step and the solution-heating and drying step are repeated to increase a thickness of the polyimide resin layer up to a predetermined value.