Diffusion cooled gas laser arrangement and method for setting the discharge distribution in the case of diffusion cooled gas laser arrangement

Abstract

A diffusion-cooled gas laser system that includes a first and a second electrode and a discharge gap arranged between the electrodes, wherein a dielectric is arranged on at least one of the electrodes on the discharge-gap side. The system is characterized in that the dielectric thickness d/.sub.res the dielectric for influencing the discharge .sub.res of distribution in the discharge gap varies along at least one dimension of the electrode on which the dielectric is arranged, wherein d is the thickness of the dielectric, and .sub.res is the resultant constant of the dielectric, and, at its thickest point, has a thickness of at least 1 mm or is greater than one hundredth of the length of the electrode or is greater than one thousandth of a wavelength determined by the frequency of a radiofrequency electrical power to be coupled into the system.

Claims

1. A diffusion-cooled gas laser system comprising: a first electrode extending from a first end to a second end along a length of the diffusion-cooled gas laser system; a second electrode extending from the first end to the second end, wherein the second electrode is connected to the first electrode such that a discharge gap is positioned between the first electrode and the second electrode along the length, wherein the diffusion-cooled gas laser system is configured to form a laser beam in the discharge gap, wherein the laser beam has a spatial expansion along at least a portion of the length; at least one dielectric element arranged on at least one of the first electrode and the second electrode, wherein the at least one dielectric element comprises at least two material components each having a different dielectric constant with respect to one another, whereby a non-zero/positive thickness of at least one material component of the at least two material components increases from a first non-zero thickness to a second non-zero thickness along at least a portion of the length of the electrode, the increase from the first non-zero thickness to the second non-zero thickness adapted to the spatial expansion of the laser beam; and a power input configured to electrically couple a power source to at least one of the first electrode and the second electrode intermediate the first end and the second end, wherein a dielectric thickness ratio d/.sub.res of the at least one dielectric element varies of along a length of the at least one dielectric element in a direction away from the power input, whereby d is the thickness of the at least one dielectric element and .sub.res is the resulting dielectric constant of the combined dielectric constants of each of the at least two material components in the at least one dielectric element.

2. The diffusion-cooled gas laser system according to claim 1, wherein the at least one dielectric element comprises a variation of the dielectric constant .sub.res along at least one dimension of the electrode, which influences the dielectric thickness ratio of the at least one dielectric element.

3. The diffusion-cooled gas laser system according claim 1, wherein the distribution of the dielectric thickness ratio along at least one dimension of the electrode is stepless.

4. The diffusion-cooled gas laser system according claim 1, wherein the distribution of the dielectric thickness ratio along at least one dimension of the electrode is stepped with at least two steps.

5. The diffusion-cooled gas laser system according to claim 1, wherein the at least one dielectric element comprises at least two material components each having a different dielectric constant with respect to one another, whereby the material components are arranged one above the other in the direction of the discharge gap and the dielectric thickness ratio d/.sub.res of the at least two material components varies along at least one dimension of the electrode.

6. The diffusion-cooled gas laser system according to claim 1, wherein the at least one dielectric element comprises at least two material components each having a different dielectric constant with respect to one another, whereby one material component is enclosed by the other material component, or is delimited by the other material component, in at least one area.

7. The diffusion-cooled gas laser system according to claim 1, wherein the at least one dielectric element comprises one or more of the materials water, ceramic, PTFE, air, and polyethylene.

8. The diffusion-cooled gas laser system according to claim 1, wherein the at least one dielectric element comprises a thickness that varies across the electrode area, wherein the at least one dielectric element is adapted to the spatial expansion of the beam with a convex structure and with an expansion that is thicker in the center of the electrodes than at the edge of the electrodes.

9. The diffusion-cooled gas laser system according to claim 1, wherein the at least one dielectric element comprises a solid material component that encloses a further non-solid material component.

10. The diffusion-cooled gas laser system according to claim 1, wherein the power input is provided centrally on one electrode and the dielectric constant .sub.res of the dielectric increases from the power input towards the edge of the electrode.

11. The diffusion-cooled gas laser system according to claim 1, wherein the gas laser system is designed as a slab laser that guides the laser beam by the electrodes.

12. The diffusion-cooled gas laser system according to claim 1, wherein the distance between the electrodes varies in at least one dimension.

13. The diffusion-cooled gas laser system according to claim 1, wherein the distance between the electrodes varies across the area of the electrodes.

14. The diffusion-cooled gas laser system according to claim 1, wherein the power source is two-dimensionally coupled into the discharge gap at a high frequency, whereby the frequency lies within a range of between at least one of 1 MHz and 300 MHz, 10 MHz and 100 MHz, and 70 MHz and 90 MHz.

15. The diffusion-cooled gas laser system according to claim 14, wherein the coupled electric power is greater than 2 kW.

16. The diffusion-cooled gas laser system according to claim 15, wherein the spatial expansion of at least one electrode area of the at least one electrode is at least 500 mm in length.

17. The diffusion-cooled gas laser system according to claim 1, wherein the dielectric thickness ratio d/.sub.res of the at least one dielectric element increases along a length of the dielectric element in a direction away from the power input.

18. The diffusion-cooled gas laser system according to claim 1, wherein the dielectric element is arcuate in a direction along the length.

19. The diffusion-cooled gas laser system according to claim 1, wherein the dielectric distribution in the discharge gap is at least one of continuous and linear.

20. The diffusion-cooled gas laser system according to claim 1, wherein the dielectric element has a thickness of at least one of: 1 mm, greater than a hundredth of the length of at least one of the first electrode and the second electrode, and greater than a thousandth of a wavelength determined by the frequency of an electric high-frequency power source configured for coupling via the power input.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1a is a partial cross-section through a diffusion-cooled gas laser system according to various embodiments of the invention.

(2) FIG. 1b is a resulting power and temperature distribution of a coaxial laser without setting the dielectric thickness for a central power input in relation to the length.

(3) FIG. 1c is a desired temperature distribution of a coaxial laser.

(4) FIG. 2 is an enlarged section of the diffusion-cooled gas laser system of FIG. 1a.

(5) FIG. 3 is a cross-sectional illustration through an electrode with two different material layers that form the dielectric.

(6) FIG. 4 is a cross-sectional illustration through an electrode with a dielectric that consists of two materials, whereby the thickness of the materials changes continuously along the at least one dimension of the electrodes.

(7) FIG. 5 is a further cross-sectional illustration through an electrode with a dielectric, whereby a material layer comprises a different thickness along at least one dimension of the electrode.

(8) FIG. 6 is a cross-sectional illustration through an electrode with a dielectric, whereby a second material layer is embedded in the first material layer.

(9) FIG. 7 is an electrode with an input that is central to the width.

(10) FIG. 8 is an electrode with an input that is central to the area.

DETAILED DESCRIPTION

(11) FIG. 1a shows a diffusion-cooled gas laser system 1 in a partial cross-sectional illustration. The gas laser system 1 comprises an external electrode 2, in which cooling tubes 3 for a coolant are arranged. The external electrode 2 is made of metal and connected to earth. The discharge gap 4 is located directly below the electrode 2. The second electrode is identified with reference number 5.

(12) A dielectric element comprising several material layers is located above this second electrode 5. A water layer 6 is first arranged on the electrode 5. Above this a material layer 7 consisting, e.g., of PTFE is located. Above this a material layer 8 consisting of water is in turn located, which is followed by a material layer 9 made of ceramic. The dielectric element on the discharge gap side of the electrode 5 in this embodiment therefore consists of four different materials, which each have their own dielectric constant .sub.r. A variation of the dielectric thickness d/.sub.res results from a thickness of the dielectric element, which is not shown here, but is instead shown only in the enlarged illustration of FIG. 2, that differs across the area or the length of the electrode in this embodiment.

(13) It is also clear from FIG. 1a that the power input electrically coupling the power source to electrode 5 is located centrally in position 10 in relation to the length of electrode 5.

(14) With a coaxial laser like the one shown in FIG. 1a, power distribution according to diagram 1b results from a central input of power. This means that the power is at a maximum at the input and then falls again towards both ends of the coaxial laser. This also leads to a temperature profile T, as shown in FIG. 1b. However, it is the temperature profile T illustrated in FIG. 1c that is desired, i.e., a constant temperature across the length of the laser. This is achieved by setting the dielectric thickness across the length of the gas laser, or across the area of the electrode 5.

(15) It can be seen from the illustration in FIG. 2 that the surface 11 of the electrode 2 as well as the surface 12 of the dielectric element 13, in particular of material layer 9, is arced. In the embodiment shown the surfaces of electrode 2 and of material layer 9, and therefore that of the dielectric element 13, display a hyperbolic arc in cross-section. As a consequence of this the dielectric thickness along the broken line 14, i.e., in the center of the electrode 5 in relation to its length is different from that along the broken line 15, i.e., at the end of the laser. With this measure and the selection of suitable materials 6-9 the power distribution, and therefore the temperature distribution, can be set across the length of the gas laser system in such a way that a constant temperature results across the length of the laser and the dielectric element.

(16) In FIG. 2 the resonator mirrors 16 and the laser beam 17, which expands in a concave fashion between the resonator mirrors 16, are also shown. The edge layer 18 abuts between the laser beam 17 and the sides of the electrode 2 or the material layer 9 facing the laser beam 17.

(17) If power were not supplied in position 10, as illustrated in FIG. 1a, but at one end, the dielectric thickness would have to be set differently to maintain a constant temperature distribution.

(18) FIG. 3 shows a cross-sectional illustration through an electrode 20, on which a dielectric 21 is located. The dielectric 21 comprises a first material layer 22 and a second material layer 23. The second material layer 23 is embedded into the first material layer 22 and progresses in steps. This means that the dielectric thicknesses are different along the lines 24, 25, 26, as the relevant dielectric constants .sub.r of the first and second material 22, 23 make different contributions towards the resulting dielectric constant .sub.res.

(19) In the illustration of FIG. 4 an electrode 30, on which a dielectric element 31 comprising a first material 32 and a second material 33 is located, is shown. The thickness of the first material 32 as well as that of the second material 33 changes continuously across the length of the electrode 30, and therefore also along at least one dimension of the electrode 30. This results in different dielectric thicknesses along the lines 34, 35, as the contributions of the materials 32, 33, with their respective different .sub.r, towards the resulting dielectric thickness vary.

(20) An electrode 40 supporting a dielectric element 41 on the discharge gap side is shown in FIG. 5. It consists of two materials 42, 43, whereby material layer 42 has a constant thickness and material layer 43 has a hyperbolic shape. The thickness of the dielectric element layer 43 therefore varies across the length or area of the electrode 40. Different dielectric element thicknesses therefore result along the broken lines 44, 45.

(21) An electrode 50 comprising a dielectric element 51 is shown in FIG. 6. The dielectric element 51 comprises a first material 52 and a second material 53, whereby the second material 53 is completely enclosed within the first material 52, and is in particular of a spherical shape. The second material 53 could, for example, consist of spherical air inclusions. As a consequence of this configuration, the dielectric element thickness along the lines 54, 55 differs.

(22) FIG. 7 shows an electrode 70 such as might for example be used with a slab laser. An input 71 that is central to the width of the electrode 70 is shown here, which is however located at one end in relation to the length of the electrode 70.

(23) An alternative input is shown for the electrode 80 in FIG. 8, where a central input in relation to the area of the electrode is realized at point 81.

Other Embodiments

(24) A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.