Method and apparatus for mounting a semiconductor disk laser (SDL)

Abstract

The present invention describes a method and apparatus for mounting a semiconductor disc laser (SDL). In particular there is described a cooling apparatus assembly (12) for mounting the semiconductor disc laser (1) the cooling apparatus assembly comprising a crystalline heat spreader (8) made of diamond, sapphire or SiC and optically contacted to the SDL (1). The apparatus further comprises a heatsink (13) made of copper and a recess (16) located on a first surface (15) of the heatsink. A pliable filler material (17) which may be In or an In alloy is provided within the recess (16) such that when a sealing plate (19) is fastened to the heatsink the SDL (1) is hermetically sealed within the recess. Hermetically sealing the SDL within the recess is found to significantly increase the lifetime of the device comprising the SDL. The heat sink (13) may be water cooled with pipes (14) delivering the water. In case the sealing plate (19) is made from for example Invar, it has an aperture (20).

Claims

1. A cooling apparatus assembly for mounting a semiconductor disc laser (SDL), the cooling apparatus assembly comprising: a crystalline heat spreader optically contacted to the SDL; a heatsink comprising a recess located on a first surface thereof; the recess filled with a mechanically pliable filler material within which the SDL is submerged; and a sealing plate fastened to the heatsink to hermetically seal the SDL within the recess.

2. The cooling apparatus assembly as claimed in claim 1 wherein the heatsink comprises copper.

3. The cooling apparatus assembly as claimed in claim 1 wherein the heat spreader comprises a diamond, sapphire or silicon carbide material.

4. The cooling apparatus assembly as claimed in claim 1 wherein the heatsink further comprises a cooling means.

5. The cooling apparatus assembly as claimed in claim 1 wherein the diameter of the crystalline heat spreader is greater than the diameter of the SDL.

6. The cooling apparatus assembly as claimed in claim 1 wherein the filler material comprises Indium or an Iridium based alloy.

7. The cooling apparatus assembly as claimed in claim 1 wherein the heatsink comprises one or more tapped holes located around the perimeter of the recess.

8. The cooling apparatus assembly as claimed in claim 1 wherein the sealing plate comprises a central aperture.

9. The cooling apparatus assembly as claimed in claim 8 wherein a diameter of the central aperture that locates with the first surface is smaller than the diameter of the crystalline heat spreader.

10. The cooling apparatus assembly as claimed in claim 8 wherein the central aperture is tapered.

11. The cooling apparatus assembly as claimed in claim 8 wherein the sealing plate further comprise one or more apertures located around the perimeter of the central aperture.

12. A method of mounting a semiconductor disc laser (SDL), the method comprising; bonding by optical contacting a crystalline heat spreader to the SDL; providing a heatsink comprising a recess located on a first surface thereof; filling the recess with a mechanically pliable filler material; submerging the SDL within the mechanically pliable filler material; and pushing the crystalline heat spreader and the SDL further into the recess by fastening a sealing plate to the heatsink to hermetically seal the SDL within the recess.

13. The method of mounting a semiconductor disc laser as claimed in claim 12 wherein the heat spreader comprises a diamond, sapphire or silicon carbide material.

14. The method of mounting a semiconductor disc laser as claimed in claim 12 wherein the filler material comprises Indium or an Indium based alloy.

15. The method of mounting a semiconductor disc laser as claimed in claim 12 wherein the sealing plate is fastened to the heatsink via one or more screws engaging with the first surface of the heatsink.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) There will now be described, by way of example only, various embodiments of the invention with reference to the drawings, of which:

(2) FIG. 1 presents a schematic representation of a semiconductor disk laser (SDL) mounted on a peltier controlled cooling block, as is known in the art;

(3) FIG. 2 presents a schematic representation of a semiconductor disk laser (SDL) that comprises a crystalline heat spreader, as is known in the art;

(4) FIG. 3 present a schematic representation of a cooling apparatus employed in conjunction with an SDL in accordance with an embodiment of the present invention; and

(5) FIGS. 4(a)-(d) present a schematic representation of a method for mounting the SDL within the cooling apparatus of FIG. 3.

(6) In the description which follows, like parts are marked throughout the specification and drawings with the same reference numerals. The drawings are not necessarily to scale and the proportions of certain parts have been exaggerated to better illustrate details and features of embodiments of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(7) Details of the method and apparatus for mounting a semiconductor disc laser (SDL) 1 will now be described with reference to FIGS. 3 and 4. In particular, FIG. 3 present a schematic representation of a cooling apparatus assembly for mounting the SDL 1, as generally depicted by reference numeral 12. FIG. 4 presents a schematic representation of the corresponding method for mounting the SDL 1 within the cooling apparatus assembly 12.

(8) The cooling apparatus assembly 12 can be seen to comprise a heatsink 13. It is preferable for the heatsink 13 to be made from copper given the relatively high thermal conductivity (κ=401 Wm.sup.1K.sup.−1) exhibited by this material, although other alternative materials may be employed. In the presently described embodiment the heatsink 13 comprises an integrated flow return pipe 14 that provides a means for a cooling liquid (e.g. water) to flow through the heatsink 13. It will be appreciated that other forms of cooling of the heatsink 13 may be employed e.g. by attaching one or more peltier devices to one or more surfaces of the heatsink 13 and thereafter separately cooling these one or more devices.

(9) Located on a first surface 15 of the heatsink 13 is a recess 16. The recess 16 is sized so as to be capable of receiving an SDL 1 that has been optically contacted with a crystalline heat spreader 8. Typically the recess 16 has a diameter of around 10 mm.

(10) In order to improve the thermal management provided by the cooling apparatus assembly 12 it is preferable for the diameter of the crystalline heat spreader 8 to be greater than that of the SDL 1.

(11) The volume of the recess 16 not occupied by the SDL 1 or the crystalline heat spreader 8 is occupied by a filler material 17. The filler material 17 is required to exhibit good thermal conductivity (κ) so as to allow heat to flow efficiently from the heat spreader 8 to the heatsink 13. For reasons that will be explained in further detail below, the filler material 17 is also required to be mechanically pliable or malleable at standard room temperature (typically 20° C.). In order to satisfy these two criteria the filler material preferably comprises Indium exhibiting a thermal conductivity κ=82 Wm.sup.1K.sup.−1. It will however be appreciated that alternative materials to Indium could be employed to function as the filler material 17 e.g. an Indium based alloy.

(12) Four tapped holes 18 are located around the perimeter of the recess 16. The tapped holes 18 are employed to provide a means for securing a sealing plate 19 to the first surface, as described in further detail below.

(13) The sealing plate 19 can be seen to comprise a central aperture 20 around the perimeter of which are located four apertures 21, the apertures 21 being arranged so as to align with the tapped holes 18 of the heatsink 13 when the sealing plate 19 is located on, and fastened to, the first surface 15 by four screws 22. The diameter of the central aperture 20 that locates with the first surface is arranged to be smaller than the diameter of the crystalline heat spreader 8. Preferably this is achieved by employing a central aperture 20 that is tapered towards the heatsink 13. The central aperture 20 provides a means for a pump field to gain access to the SDL 1, via the crystalline heat spreader 8, and also for the generated output field to exit the cooling apparatus assembly 12. The preferred material for the sealing plate 19 is Invar®. Invar®, also known generically as FeNi.sub.36, is a nickel iron alloy notable in the art for its uniquely low coefficient of thermal expansion.

(14) Advantageously, when the sealing plate 19 is fastened to the first surface 15 by the four screws 22 it acts to hermetically seal the SDL 1 within the recess 16. At this time the filler material 17 provides mechanical support to the SDL 1 while also providing it with a good thermal contact with the heatsink 13.

(15) Method for Mounting an SDL

(16) The method for mounting the SDL 1 will now be described with reference to FIG. 4.

(17) In the first instance the heat spreader 8 is bonded by means of optical contacting with the SDL 1, as presented in FIG. 4(a).

(18) Next a pliable filler material 17 is located within the recess 16 of the heatsink 13, as presented schematically in FIG. 4(b).

(19) The penultimate step is presented in FIG. 4(c) whereby the heat spreader 8 and SDL 1 assembly is located within the recess 16. At this stage the SDL 1 is submerged within the filler material 17 while a portion of the heat spreader 8 generally remains protruding from the recess 16.

(20) Finally, the sealing plate 19 is located upon, and fastened to, the first surface 15 of the heatsink 13 by threading the four screws 22 through the four apertures 21 and into the corresponding tapped holes 18. The pliable or malleable nature of the filler material 17 allows for the heat spreader 8 and SDL 1 assembly to be pushed down into the recess 16, without causing any damage to the SDL 1, until the previously exposed surface of the heat spreader 8 lies flush with the first surface 15. The resulting effect is that the SDL 1 is hermetically sealed within the recess 16. The pliable filler material 17 also provides mechanical support to the SDL 1 and provides it with a good thermal contact with the heatsink 13.

(21) The above described method and apparatus for mounting an SDL 1 offer a number of advantages over those know in the prior art. In the first instance, the effects of evaporation on the optical contact between the heat spreader 8 and the SDL 1 are significantly reduced as a direct result of the presence of the hermetic seal. Hermetically sealing the SDL 1 within the recess 16 also significantly reduces the ingress of foreign bodies upon the gain medium of the SDL 1. The combined effects on the described cooling apparatus assembly 12 is that any SDL 1 based device which incorporates this apparatus and methodology experiences a significantly increased operating lifetime.

(22) The present invention describes a method and apparatus for mounting a semiconductor disc laser (SDL). In particular there is described a cooling apparatus assembly for mounting the semiconductor disc laser (SDL) the cooling apparatus assembly comprising a crystalline heat spreader optically contacted to the SDL. The apparatus further comprises a heatsink and a recess located on a first surface of the heatsink. A filler material is provided within the recess such that when a sealing plate is fastened to the heatsink the SDL is hermetically sealed within the recess. Hermetically sealing the SDL within the recess is found to significantly increase the lifetime of the device comprising the SDL.

(23) Throughout the specification, unless the context demands otherwise, the terms “comprise” or “include”, or variations such as “comprises” or “comprising”, “includes” or “including” will be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers.

(24) Furthermore, reference to any prior art in the description should not be taken as an indication that the prior art forms part of the common general knowledge.

(25) The foregoing description of the invention has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed. The described embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilise the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Therefore, further modifications or improvements may be incorporated without departing from the scope of the invention as defined by the appended claims.