Abstract: A gas discharge tube for a gas laser includes a discharge chamber having a first end and a second end. A cathode is mounted near the first end in a cathode region of the discharge chamber and an anode is mounted near the second end. An electromagnet induces an axial magnetic field within the discharge region, and a pole piece is mounted on the end of the electromagnet adjacent the cathode region. By using a pole piece for attenuating the axial magnetic field in the cathode region, a significant reduction in 60-60 Hz modulation of the light beam is realized, as well as a reduction of sputtering in the throat region of the discharge tube, additionally, the cathode placement relative to the throat region may be optimized leading to an increase in plasma tube efficiency. In addition, a second pole piece is mounted on the end of the electromagnetic coil, adjacent the anode region, for attenuating the axial magnetic field inside the anode region after the discharge reaches the anode.

Abstract: An apparatus for applying a load to an etalon so as to enable the accurate tuning of desired frequencies or ranges of frequencies. The invention includes first and second optical surfaces separated and disposed highly parallel with respect to each other by an electric longitudinal spacer member. A biasing means applies a longitudinal load to the elastic longitudinal spacer member. The applied load is uniformly distributed throughout the spacer member by a longitudinal load distribution means, which is disposed between said biasing means and at least one of said optical surfaces. The distance, d, between the first and second optical surface is directly proportional to the load applied by the biasing means. The load may be varied, in one embodiment of the invention, using a bias adjustment means acting in mechanical cooperation with the biasing means.

Abstract: Alignment of a birefringent device characterized by a first face and a second face cut at Brewster's angle so that a plane of polarization is defined. The optical device is secured in the optical path by a rotatable member having an axis of rotation that is normal to the Brewster faces of the optical device. Coupled with the rotatable member on the axis of rotation is a support allowing adjustment of the angular position about the axis of rotation of the rotatable member. An operator adjusts the angular position of the rotatable member until the C-axis lies in the plane of polarization. Even though the C-axis may not be parallel to the direction of polarization, the depolarization effects of the misalignment are eliminated by proper adjustment of the angular position relative to the plane of polarization. A tunable, solid state laser using the alignment apparatus with a birefringent filter achieves greater linear tuning range.