A gas discharge laser includes a laser capillary in a tubular glass envelope which has at its two ends reflectors having optical axes which coincide with the axis of the laser capillary and which together constitute a laser resonator. A Brewster window is mounted in the envelope immediately before one of the reflectors. The Brewster window is placed in a holder manufactured from metal sheet material so that one side thereof is pressed against three regions of engagement on the holder whereby no mechanical stresses occur in the Brewster window. These stresses would otherwise disturb the polarizing effect of the Brewster window. This holder can be manufactured with small tolerances and in a very cheap manner.
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.
The effects of random polarization of a laser beam is reduced by separating the polarized laser beam into first and second polarized components that are orthogonal to each other, and measuring the energy in each of the first and second components. The total energy in both of the first and second components are compared with a predetermined energy level. The energy output of the laser beam is controlled in response to the measured comparison.
