Gas laser device
A gas laser device is presented that produces a near diffraction limited round beam exiting the discharge vessel. Through the use of a simple focusing system, additional waveguide strip and a spatial filter in conjunction with the new asymmetric hybrid planar waveguide resonator, a round diffraction limited beam can be produced exiting the discharge vessel. Furthermore, a second and very similar design is presented that allows for spatial filtering to take place directly outside of the discharge vessel, thereby enabling filtering of the beam to be an added option.
1. A gas laser device comprising: two substantially parallel electrode plates forming a waveguide operable to focus and reflect a laser resonator beam; excitation means operable to cause a gas discharge; first and second reflecting means facing each other between the electrode plates to form a resonator, respective radii of curvature and a separation of the first and second reflecting means being such that the resonator in the free space plane parallel to the electrode plates is unstable and substantially confocal, and wherein said second reflecting means has a hard edge and has a radius of curvature in the free-space unstable direction that is greater than the radius of curvature of the first reflecting means; and third reflecting means, physically distinct from the first and second reflecting means, directing light through an additional waveguide element to an exit of the gas laser; wherein the additional waveguide element is external to the resonator and located between the third reflecting means and the exit of the gas laser, wherein the third reflecting means is adjacent one end of the resonator and the exit of the gas laser is adjacent an opposite end of the resonator.
2. A gas laser device as claimed in claim 1 , characterized by being adapted to out-couple the resonator beam past the second reflecting means, the latter having a radius of curvature such that the exit beam is divergent and exits at an angle to a longitudinal axis of the unstable resonator.
3. A gas laser device as claimed in claim 1 , wherein the third reflecting means are operable to focus the resonator exit beam substantially at an exit of the additional waveguide element to form a beam waist in the free space direction substantially the same size as a beam waist formed in the orthogonal waveguide direction.
4. A gas laser device as claimed in claim 3 , further including spatial filtering means operable to shape the beam for use and located substantially at the exit of the additional waveguide element and adapted to remove side lobes in the free space direction to thereby generate a diffraction limited round beam internal to the laser gas device.
5. A gas laser device as claimed in claim 1 , wherein the third reflecting means are operable to focus the resonator exit beam in the free space direction beyond the exit of the additional waveguide element.
6. A gas laser device as claimed in claim 5 , further including spatial filtering means placed substantially at the free space beam waist and adapted to remove side lobes of the beam in the free space direction to thereby generate a diffraction limited beam.
7. A gas laser device as claimed in claim 5 , further including an optical element that is located where the orthogonal free space and waveguide beam sizes are substantially the same, and has an optical power such that the different divergences in the orthogonal directions are made substantially the same, thereby generating a round diffraction limited beam.
8. A gas laser device as claimed in claim 5 , further including a spatial filter means and an optical element.
9. A gas laser device as claimed in claim 1 , wherein the additional waveguide element is adjacent to and coplanar with the waveguide formed by the electrode plates.
10. A gas laser device as claimed in claim 1 , wherein the third reflecting means are adjustable in angle.
11. A gas laser device as claimed in claim 1 , wherein the first and second reflecting means have radii of curvature to form a near confocal resonator in the plane parallel to the electrode plates.
12. A gas laser device as claimed in claim 1 , wherein a discharge is created by radio frequency excitation of the gas contained within the gap between the substantially parallel electrode plates.
13. A gas laser device comprising: two substantially parallel electrode plates forming a waveguide operable to focus and reflect a laser resonator beam; excitation means operable to cause a gas discharge; first and second reflecting means facing each other between the electrode plates to form a resonator, respective radii of curvature and a separation of the first and second reflecting means being such that the resonator in the free space plane parallel to the electrode plates is unstable and substantially confocal, and wherein said second reflecting means has a hard edge and a concave radius of curvature in the free-space unstable direction; and third reflecting means, physically distinct from the first and second reflecting means, directing light through an additional waveguide element to an exit of the gas laser; wherein the additional waveguide element is external to the resonator and located between the third reflecting means and the exit of the gas laser, wherein the third reflecting means is adjacent the hard edge and the exit of the gas laser is adjacent an opposite end of the resonator.