Laser with improved cooling system

• US 4,881,233 A
• Filed: 06/22/1988
• Issued: 11/14/1989
• Est. Priority Date: 06/22/1987
• Status: Expired due to Term

• Current Assignee: Lasag AG Steffisburgstrasse 1 3600 THUN / Switzerland
• Original Assignee: Lasag AG Steffisburgstrasse 1 3600 THUN / Switzerland
• Inventors: Durr, Ulrich, Gressly, Andre, von Arb, Hans-Peter, Studer, Franz
• Primary Examiner(s): Davie, James W.
• Application Number:
  US07/209,708
• Time in Patent Office: 510 Days
• Field of Search: 372/34, 372/35, 372/66, 372/70, 372/72
• US Class Current: 372/35
• CPC Class Codes: H01S 3/025 of solid state lasers, e.g. housings or mountings
• CPC Class Codes: H01S 3/0407 Liquid cooling, e.g. by water
• CPC Class Codes: H01S 3/042 for solid state lasers H01S3/0401 takes precedence
• CPC Class Codes: H01S 3/0606 with polygonal cross-section, e.g. slab, prism H01S3/0604 takes precedence
• CPC Class Codes: H01S 3/08095 Zig-zag travelling beam through the active medium
• CPC Class Codes: H01S 3/093 focusing or directing the excitation energy into the active medium

Abstract

A laser has a slab in which the beam F is propagated in zig-zag manner between two opposing faces which have the property of ensuring total reflection. For this purpose each of these faces is covered with a solid layer of a good heat conducting material and having a refractive index below that of the slab. Its thickness is preferably greater than three times the operating wavelength of the laser. Thus, a cooling fluid can be in contact with the solid layer to effectively cool the slab. Pumped energy sources are preferably provided opposite the layers.

Claims

1. A cooled optical pumped laser having a laser medium in the form of a slab, said slab having at least two opposing parallel pumping faces between which a laser beam develops by propagation along a zig-zag path by means of total reflection between said opposing parallel pumping faces whereby a monolayer of solid material is directly applied to each one of said opposing parallel pumping faces, said solid material having a refractive index less than that of the slab and being at least indirectly in heat exchanging relationship with a cooling fluid, and wherein the material of said monolayer of solid material is transparent to the optical energy used to excite the medium of said slab.

2. A laser according to claim 1, wherein each of said layer of solid material is applied to each pumping face of the slab by a physical or chemical deposition process.

3. A laser according to claim 1, wherein the thickness of the layer of solid material is at least three times the operating wavelength of the laser.

4. A laser according to claim 1, wherein said layer of solid material is formed of a metal oxide or composite metal oxide.

5. A laser according to claim 4, wherein said metal oxide or composite metal oxide is selected from the group consisting of Al₂ O₃, SiO₂ or CaO.SiO₂.

6. A laser according to claim 1, wherein said layer is formed of a halide.

7. A laser according to claim 6, wherein the layer of solid material is formed of a halide selected from the group consisting of MgF₂, BaF₂, AlF₃, CaF₂, LaF₃ or NdF₃.

8. A laser according to claim 1, wherein said layer of solid material is doped with transition metal ions or rare earths.

9. A laser according to claim 8, wherein the transition metal ions or rare earths are selected from the group consisting of titanium (Tti), chromium (Cr), erbium (Er) or thulium (Tm).

10. A laser according to claim 1, wherein each layer of solid material applied to the parallel faces of the slab is covered by at least one second layer of a material that is a good heat conductor.

11. A laser according to claim 10, wherein said second layer is transparent to the optical energy serving to excite the medium of said slab.

12. A laser according to claim 11, wherein said second layer is applied to the first layer by means of a physical or chemical deposition process.

13. A laser according to claim 10, wherein said second layer is in the form of a sheet and is affixed to said first layer.

14. A laser according to claim 10, wherein said second layer is formed of a metal oxide selected from the group consisting of SiO₂, Al₂ O₃, CaO.SiO₂ or BeAl₂ O₄.

15. A laser according to claim 10, wherein said second layer is formed of a metal halide.

16. A laser according to claim 15, wherein the metal halide forming said second layer is selected from the group consisting of MgF₂, AlF₃, CaF₂, LiF or KMgF₃.

17. A laser according to claim 10, wherein a third anti-reflective layer is applied on said first or second layers.

18. A laser according to claim 10, wherein said second layer is held in place by a foil of transparent material that extends beyond the area of this second layer.

19. A layer according to claim 1, wherein the faces of the slab other than those with which the said first layer are in contact are exposed to a heat insulating medium such as air or nitrogen.