Abstract: A metallic member is disposed in the vicinity of a mirror within an internal mirror type gas laser tube, and an electric discharge is excited between an internal laser anode and the metallic member. The metallic member serves as a cathode to sputter the metal of the metallic member onto the surface of the internal mirror. The metal adheres to the surface of the mirror and forms a metallic film thereon. The output power of the lower tube is monitored during the sputtering process and the sputtering process is terminated when the output power is reduced to a desired output power value.

Abstract: A gas laser tube includes a metal supporting body installed at one end of the laser tube. A seal casing is secured to the supporting body, and accommodates at least one cylindrical holding body having one end cut to a Brewster angle, and an optical flat plate installed in close contact with the cut surface of the holding body. A reflecting mirror is secured to an end of the seal casing.