A window assembly for a laser uses a uniaxial crystalline material such as quartz for the window, secured directly in a hard seal to a metal tubular end component. In order to avoid significant differential thermal expansion between the quartz window and the end component, the quartz crystal is cut in a Z-normal configuration, whereby the thermal expansion and other physical properties of the window are isotropic in the plane of the window. The ability to make a reliable direct seal to a metal component offsets any disadvantages of the Z-normal configuration thought to be controlling in the prior art. Through the disclosed method for assembling and mounting the window, reflection loses are reduced to a practical minimum comparable to that of any preferred conventional window orientation.

A gas laser is disclosed, in which one end surface of a plasma tube of a gas laser envelope is worked to be perpendicular to the axis of the plasma tube, a cap covers a mirror and the end surface of the plasma tube so as to make the mirror abut against the worked end surface, the cap is fixed at its open end to the plasma tube by frit material, and a bore is formed through the plasma tube which is covered by the cap.

A linearly polarizing internal mirror type gas laser tube comprises a channel-shaped holder pair for axially compressively holding a Brewster plate in a hollow cylindrical space surrounded by an inside surface of a pipe. Each holder comprises a side wall pair and a connecting wall connecting the side wall pair. Each side wall has a pair of protrusions having a common axial end plane that provides the Brewster angle. The holders are brought into contact with the Brewster plate with the protrusions made to contact with corner portions of the plate. The side walls may have free ends spaced apart from the pipe inside surface. Alternatively, the side walls of at least one of the holders may have outwardly bent portions having free ends brought into contact with the pipe inside surface. It is readily possible to press shape the holders at low costs from a metal sheet.

An internal mirror type gas laser tube having mirrors at the opposite ends thereof supported by hollow flexible metallic members to allow for mirror adjustment. The hollow members include a support pipe, provided outside of the hollow metallic member, the support pipe being covered by a thermocontractive insulating material. The insulating material eliminates electrical shock hazards which are present when the metallic member assumes the high voltage potential utilized to operate the laser.

A hollow mirror seat, insertable into the end of a laser tube, has a first portion having a first length and a first outside diameter close to the inside diameter of the laser tube. A second portion of the mirror seat has a second length and a second outside diameter smaller than the inside diameter of the laser tube. A portion of the second length has a region of reduced wall thickness around its entire circumference.