Laser pump cavity

• US 5,619,522 A
• Filed: 09/07/1995
• Issued: 04/08/1997
• Est. Priority Date: 09/07/1995
• Status: Expired due to Fees

• Current Assignee: Dube, George
• Original Assignee: Dube, George
• Inventors: Dube, George
• Primary Examiner(s): Scott, Jr., Leon
• Application Number:
  US08/524,593
• Time in Patent Office: 579 Days
• Field of Search: 372/72, 372/92, 372/34, 372/6, 372/66, 372/75
• US Class Current: 372/72
• CPC Class Codes: H01S 3/025 of solid state lasers, e.g. housings or mountings
• CPC Class Codes: H01S 3/0404 Air- or gas cooling, e.g. by dry nitrogen
• 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 3/061 with elliptical or circular cross-section and elongated shape, e.g. rod
• CPC Class Codes: H01S 3/094084 with pump light recycling, i.e. with reinjection of the unused pump light, e.g. by reflectors or circulators
• CPC Class Codes: H01S 3/0941 of a laser diode

Abstract

A laser pump includes a pump housing defining a pump cavity. The pump cavity includes reflecting walls having two or more sections, which in combination, encircle the laser element of the laser. The two or more sections have centers which are off-set from each other and which may be of different radii or height. The longitudinal axes of the segments are parallel to the center of the laser element, and the center of one of the segments may be coaxial with the axis of the laser element. Pump light enters the pump cavity through one or more openings in the housing into the cavity and is reflected many times by the reflecting surfaces of the cavity, passing many times in various directions through various parts of the laser element, resulting in efficient and uniform pumping of the laser element.

Claims

1. A laser pump including a pump housing defining a pump cavity, a pump light source positioned with respect to said housing to emits a pump light into said cavity, a laser element mounted within the pump cavity and a reflective surface in said pump cavity;

said reflective surface including at least a first section having a longitudinal axis and a second section having a longitudinal axis;

said first section longitudinal axis being parallel to and off-set from said second section longitudinal axis;

the pump light source directing the pump light towards one or both of said reflective surface and said laser element, the reflective surface reflecting the pump light through the laser element to create a symmetric deposition of pump light in the laser element.

2. The laser pump of claim 1 wherein the first section longitudinal axis and the second section longitudinal axis lie on the same diameter of the laser element.

3. The laser pump of claim 1 wherein the first section and the second section define an arc of a circle, said arc of the first section having a radius larger than the arc of the second section, the longitudinal axis of the second section being coaxial with an axis of the laser element.

4. The laser pump of claim 1 where in the first section and second section each comprise at least a first planar surface and a second planar surface, said first and second planar surfaces being angled with respect to each other, said first section having a first axis of symmetry and said second section having a second axis of symmetry, said first and second axes of symmetry being spaced from each other.

5. The laser pump of claim 1 including means for cooling the laser element, the cooling means partially absorbing the light emitted by the laser element.

6. The laser pump of claim 5 in which the cooling means fluoresces into some or all of the laser element pump bands to pump the laser element.

7. The laser pump of claim 6 wherein the pump source pumps one or both of the fluorescent material and the laser material.

8. The laser pump of claim 1 including means for cooling the laser element, and wherein the means for cooling the laser element includes a cooling fluid surrounding the laser element and circulating in the pump cavity, said reflective surface comprising an inner surface of said pump housing.

9. The laser pump of claim 1 including means for cooling the laser element and wherein the means for cooling the laser element includes a hollow sleeve which receives said laser element, said sleeve having an inner surface in heat transfer relationship with an outer surface of said laser element and an outer surface in heat transfer relationship with said pump housing, said sleeve being substantially transparent to the light which pumps said laser element, said reflective surface comprising of one of said sleeve outer surface and said housing inner surface.

10. The laser pump of claim 9 wherein the hollow sleeve is a one-piece unitary sleeve.

11. The laser pump of claim 9 wherein the hollow sleeve is made of two or more elongate segments.

12. The laser pump of claim 9 wherein the outer surface of the laser element is coated with a coating to fill any space between said laser element and said sleeve, said coating being generally transparent to said pump light, having a high thermal conductivity, and having a refractive index nominally equal to the refractive index of the laser element.

13. The laser pump of claim 12 wherein said coating comprises a settable material which secures said laser element in said sleeve inner when said material sets.

14. The device of claim 9 wherein the laser element comprises at least two axially aligned segments, said laser segments being received by said sleeve.

15. The laser pump of claim 9 wherein said sleeve includes an internal passage through which cooling fluid circulates.

16. The laser pump of claims 1 wherein said pump housing has a passage therein through which cooling fluid circulates.

17. The laser pump of claim 1 in which radially asymmetric cooling of the cooling sleeves is used to make the cooling of the laser element more symmetric.

18. The laser of claim 1 wherein said pump light source is mounted externally of said pump cavity, said pump housing defining an opening therein though which said pump light enters said pump cavity, said gap being closed by a surface transparent to said pump light.

19. The laser pump of claim 18 wherein said surface which closes said pump light entry gap is coated with an anti-reflective coating.

20. The laser pump of claim 1 wherein the pump housing is a unitary, one-piece housing.

21. The laser pump of claim 1 wherein the pump housing comprises two or more elongate sections.

22. The laser pump of claim 21 wherein said sleeve comprises at least two elongate parts, said elongate parts having generally flat abutting surfaces defining a gap therebetween;

a material filling said gap, said material having an index of refraction nominally equal to the index of refraction of said sleeves such that said flat abutting surfaces do not interfere with the travel of light through said cavity.

23. The laser pump of claim 1 wherein the reflective surface reflects the pump light through the laser element to create a uniform deposition of pump light in the laser element.

24. A laser including a laser pump, the laser pump having a pump housing, the pump housing comprising an inner surface defining a laser pump cavity, and a reflective surface and a laser element contained within the cavity;

the reflective surface being generally parallel to the laser element;

the reflective surface including at least a first section and a second section;

said first section defining an arc of a cylinder having a longitudinal axis and a radius;

said second section defining an arc of a cylinder having a longitudinal axis and a radius;

said first section longitudinal axis being parallel to and off-set from said second section longitudinal axis, the reflective surface reflecting the pump light through the laser element to create a symmetric deposition of pump light in the laser element.

25. The laser of claim 24 wherein the ratio of the radius of the first section to the radius of the second section is from about 3:

1 to about 1;

1.

26. The laser of claim 24 wherein said pump housing comprises at least two elongate portions.

27. The laser of claim 26 wherein said at least two pump housing portions are identical, said portions being offset from each other.

28. A laser pump including a pump light source and a pump housing, the pump housing having an inner surface defining a laser pump cavity, and a reflective surface and a laser element contained within the cavity;

the reflective surface being generally parallel to the laser element, the reflective surface being generally arcuate and defining at least a first radius and a second radius, said first radius being smaller than said second radius, said first radius having a first origin and said second radius having a second origin, said first and second origins being off-set from each other, the reflective surface reflecting the pump light through the laser element to create a symmetric deposition of pump light in the laser element.

29. The laser pump of claim 28 wherein said reflective surface defines a spiral.

30. The laser pump of claim 28 wherein said housing is a unitary, one-piece housing, said reflective surface being a continuous uninterrupted surface.

31. The laser pump of claim 28 wherein the pump housing receives a sleeve, said sleeve supporting said laser element in said housing;

said sleeve being a unitary, one-piece sleeve having a continuous, uninterrupted outer surface;

said outer surface being highly reflective to said pump light and defining the reflective surface.

32. A modular laser pump including:

a housing defining a cavity and having an inner surface;

an inner sleeve received in the housing cavity, the inner sleeve having an inner surface and an outer surface and defining an elongate opening;

a laser element received in the elongate opening of the inner sleeve to be supported in the pump cavity;

a pump light which introduces light into the pump cavity to pump the laser element;

a reflective surface, the reflective surface comprising one of the inner surface of the housing and the outer surface of the inner sleeve, said reflective surface including at least a first section having a longitudinal axis and a second section having a longitudinal axis;

said first section longitudinal axis being parallel to and off-set from said second section longitudinal axis;

the reflective surface reflecting the pump light through the laser element to create a symmetric deposition of pump light in the laser element; and

a settable material which is generally transparent to the pump light and which is positioned between an outer surface of said laser element and the inner surface of the inner sleeve to secure the laser element in position in the inner sleeve, the settable material being softenable to allow for the laser element to be removed from the pump cavity.

33. The modular laser pump of claim 32 wherein the settable material is a silicone which may be softened by the application of heat or a solvent.

34. The modular laser pump of claim 33 wherein the laser element can be slid out of the inner sleeve after the settable material has been softened.

35. The modular laser pump of claim 32 wherein the inner sleeve comprises at least a first portion and a second portion.

36. The modular laser pump of claim 32 wherein the housing comprises at least a lower portion and an upper portion, wherein the upper and lower portions are secured together to position the inner sleeve and laser element within the housing.

37. A method of removing and replacing a laser element of a modular laser pump, the laser pump including a housing defining a cavity and having an inner surface;

a pump light which introduces light into the pump cavity;

an inner sleeve received in the housing cavity, the inner sleeve having an inner surface and an outer surface and defining an elongate opening;

the laser element being received in the elongate opening of the inner sleeve to be supported in the pump cavity;

a coating which fills any space between the laser element and the inner sleeve, the coating being generally transparent to the pump light and softenable upon the application of heat or a solvent;

a reflective surface about the laser element including at least a first section having a longitudinal axis and a second section having a longitudinal axis, said first section longitudinal axis being parallel to and off-set from said second section longitudinal axis;

the reflective surface reflecting the pump light through the laser element to create a symmetric deposition of pump light in the laser element;

said method including applying heat or a solvent to said coating to melt said coating, sliding the laser element from the inner sleeve, and inserting a second laser element into the sleeve.

38. The method of claim 37 including a step of cleaning any remaining coating from the inner surface of the inner sleeve prior to the step of inserting the second laser element into the inner sleeve.

39. The method of claim 38 including a step of applying the coating material to the second laser element prior to inserting the second laser element into the inner sleeve.