High-Power Fiber Array Assembly with Built-in Cooling Device

Abstract

An optical fiber array assembly for high power applications includes a support structure, an optical fiber array, a plurality of end caps, and a fluid conduit arrangement. The optical fiber array extends through the support structure and has a plurality of optical fibers extending in a common longitudinal direction. The plurality of end caps are arranged such that each of the end caps is attached to an end portion of one of the optical fibers. The fluid conduit arrangement has one or more conduits extending through the support structure. The one or more conduits are configured to support a flow of fluid therein for removing heat resulting from optical energy reflected back from the end caps into the support structure.

Description

Technical Field

[0001] (Cross - Reference to Related Applications) This application claims the benefit of U.S. Provisional Patent Application No. 63 / 313,998, filed Feb. 25, 2022, the content of which is incorporated herein by reference.

Background Art

[0002] The demand for high optical power delivered via fiber optic arrays for multiple applications such as laser cutting and welding, additive manufacturing, directed energy weapons, etc. continues to grow. Since the light transmitted in these systems is of high power, there is heat accumulation in the fiber optic assembly, along with various optical elements and reflections from stray light energy. It is necessary to reduce and dissipate this heat so that the fiber optic array functions efficiently and does not get damaged.

Summary of the Invention

[0003] According to one aspect of the subject matter described herein, a fiber optic array assembly for high - power applications includes a support structure, a fiber optic array, a plurality of end caps, and a fluid conduit device. The fiber optic array extends through the support structure and has a plurality of optical fibers extending in a common longitudinal direction. The plurality of end caps are arranged such that each of the end caps is attached to an end portion of one of the optical fibers. The fluid conduit device has one or more conduits extending through the support structure. The one or more conduits are configured to support a flow of fluid therein to remove heat generated from light energy that is retro - reflected from the end caps and enters the support structure.

[0004] In another particular embodiment, the one or more conduits include at least one channel formed within the support structure.

[0005] In yet another particular embodiment, the one or more conduits include at least one tube extending through the support structure.

[0006] In another specific embodiment, the support structure includes a void positioned to receive the retroreflected light energy. One or more conduits extend across a plurality of optical fibers within the optical fiber array, thereby including a first conduit having a first conduit segment that receives the retroreflected light energy as light and / or heat entering the support structure through the sidewalls defining the void.

[0007] In another specific embodiment, the first conduit segment extends across the plurality of optical fibers on a first side of the optical fiber array, and the array assembly further includes a second conduit having a second conduit segment that extends across the plurality of optical fibers on a second side of the optical fibers opposite the first side of the optical fiber array.

[0008] In another specific embodiment, each of the first and second conduits has an inlet and an outlet through which fluid flows in and out, respectively.

[0009] In another specific embodiment, the sidewalls of the void have an absorption coating that absorbs the retroreflected light energy.

[0010] In another specific embodiment, the support structure transmits the retroreflected light energy, and the fluid flowing within the one or more conduits includes an absorption die that absorbs the retroreflected light energy.

[0011] In another specific embodiment, the optical fiber array assembly further includes a third conduit segment that extends across a plurality of end caps to remove the light energy that retroreflects from the end caps and enters the support structure from the circumferential sidewalls of the end caps.

[0012] In another specific embodiment, the optical fiber array assembly further includes a closed-loop conduit containing a fluid and having an absorption die therein that absorbs the retroreflected light energy. The closed-loop conduit is located closer to the optical fiber than the first conduit in the radial direction such that the heat absorbed by the closed-loop conduit flows through the support structure to the first conduit.

[0013] In another specific embodiment, the support structure includes an upper and a lower support structure that fit together with the optical fiber array positioned therebetween, and the upper and lower support structures each include corresponding notches that define a void when the upper and lower support structures are fitted together.

[0014] In another specific embodiment, one or more conduits each include a first and a second conduit that extend into the upper and lower support structures. The first and second conduits are symmetrically arranged relative to each other around the mating surface where the upper and lower support structures contact.

[0015] This "Summary of the Invention" is provided to introduce in a simplified form various concepts that are further described below in the "Detailed Description of the Invention". This "Summary of the Invention" is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. Further, the claimed subject matter is not limited to implementations that solve any or all of the disadvantages described in any part of this disclosure.

Brief Description of the Drawings

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Best Mode for Carrying Out the Invention

[0017] FIG. 1 shows a schematic exploded perspective view of an example of a high-power fiber array assembly in which cooling conduits such as channels or tubes can be incorporated to remove heat that can accumulate as a result of the adoption of high power. The array of optical fibers 1 is fixed between a lower support structure 3a and an upper support structure 3b, and these support structures, when mated, together define the support structure 3. The fiber end cap 2 is attached to the end portion of the optical fiber 1 from which the light propagating within the optical fiber 1 exits. If the energy density becomes too high, the end face of the fiber can be damaged, which in turn can cause the failure of the array. This damage occurs at the glass-air interface. The fiber end cap 2, which can be fused to the optical fiber end face, reduces this damage by allowing a larger area for the light to exit, resulting in a reduction in the energy density at the glass-air interface, and thus reducing or eliminating the damage occurring to the optical fiber 1. FIG. 2 shows the front view of the fiber array assembly in which the fiber end cap 2 is visible between the lower support structure 3a and the upper support structure 3b. Note that in FIGS. 1 and 2, and the subsequent figures, the same elements are denoted by the same reference numerals.

[0018] The optical fibers 1 are generally arranged parallel to each other and extend longitudinally along the lower support structure 3a. The lower support structure 3a includes a notch 30a having a width in the longitudinal direction across which each of the optical fibers 1 extends. The notch 30a is defined by the side walls of the ridges 31 and 33. A corresponding notch 30b is located in the upper support structure 3b.

[0019] The fiber end cap 2 is supported by the raised portion 31 and can be positioned within a V-groove defined therein. Similarly, the optical fiber 1 can be supported by the raised portions 32 and 33. In some cases, a suitable adhesive such as epoxy can be used to fix the end cap 2 and the optical fiber 1 to the support structure. The optical fiber 1 is generally surrounded by a fiber jacket, and it should be noted that the fiber jacket is removed in the region including the location where the optical fiber 1 crosses the width of the notch 30a as seen in FIG. 1.

[0020] The upper support structure 3b and the lower support structure 3a can be formed from a wide range of different materials. Exemplary examples can include glass that can transmit the operating wavelength of light used in a high-power fiber array assembly, as well as metals and metal alloys, and the like.

[0021] FIG. 3 shows in more detail the fiber end cap 2 surrounding the emitting end of one of the optical fibers 1. As shown, light 20 propagates from the optical fiber 1 into the end cap 2 and exits the end cap 2 as light 21 that spreads over a wider area compared to the light propagating within the optical fiber 1. Also shown is the light 22 that retro-reflects through the fiber end cap 2. The retro-reflected light 22 exits the fiber end cap 2 as light 23 at various points along the outer periphery of the end cap 2 and at the incident surface where the optical fiber 1 contacts the end cap 2. This light can be absorbed by the support structure and converted into heat, which can then be contained within the fiber array assembly. However, as the output increases, the fiber assembly becomes hotter, leading to failure of various components of the fiber array assembly, such as the epoxy used to construct the fiber array assembly. The epoxy can release gas from particles that can reach the end face of the optical system, resulting in further failure.

[0022] Figures 4, 5, and 6 illustrate an embodiment of a cooling channel that can be incorporated into the high-power fiber array assembly shown in FIG. 1 to mitigate the adverse effects of heat. FIG. 4 is a side view in which the optical fiber 1 is disposed in a horizontal plane extending into the page. FIGS. 5 and 6 are perspective views of a fiber array assembly without an upper support structure 3b and a fiber array assembly having the upper support structure 3b in a predetermined position, respectively. As shown, a lower cooling channel 4a is formed within the lower support structure 3a, and an upper cooling channel 4b is formed within the upper support structure 3b. The lower cooling channel 4a each has an inlet and an outlet channel segment through which a cooling fluid (e.g., a liquid such as distilled water or other having a higher heat capacity, a gas such as nitrogen, etc.) enters and exits the lower cooling channel 4a. In this example, the inlet and outlet channel segments extend generally parallel to the optical fiber 1. The transverse channel segment is in fluid communication with the inlet and outlet channel segments and extends across the array of optical fibers 1 and parallel to the sidewalls of the notch 30a. That is, the inlet and outlet channel segments and the transverse channel segment form a continuous channel, and the transverse channel segment extends parallel to the sidewalls of the notch 30b. In the example shown in FIGS. 4 and 6, the upper cooling channel 4b is arranged in a symmetric manner with respect to the upper cooling channel, but this is not essential. Further, in some embodiments, only one of the lower cooling channel 4a and the upper cooling channel 4b may be employed.

[0023] As best seen in the side view of FIG. 4, the reflected light 23 that diverges inversely from the fiber end cap 2 toward the optical fiber 1 enters the void defined by the upper notch 30b and the lower notch 30a and is then absorbed as light and heat energy 8 by the sidewalls of the notches 30b and 30a defined within the upper and lower support structures. The transverse channel segment is positioned in the support structure as close as practical to the void, thereby maintaining structural integrity. In this way, the transverse channel segment can absorb the light and / or heat 8 that enters the support structure after crossing the void.

[0024] In some embodiments, an absorptive material may be coated on the sidewalls of the upper notch 30a and the lower notch 30b to absorb the light retroreflected from the fiber end cap 2. In an alternative embodiment, if the support structure is formed from a material such as glass that transmits the optical energy within the optical fiber, the cooling fluid of the cooling conduit may include an absorption die for absorbing the reflected light entering the support structure.

[0025] In some embodiments, the cooling channels 4a and 4b may have diameters in the range of as little as 1 millimeter to several millimeters, depending on various factors including the number and size of the optical fibers in the array and the amount of output transmitted through them. Generally, the diameter of the cooling channels is larger than the diameter of the optical fibers and, in some typical high-power applications, can range from several hundred microns to over 1 millimeter. The cooling channels can be formed by any suitable technique such as laser etching using femtosecond lasers or by 3D printing techniques that can be used to form the support structure.

[0026] Figures 7-9 show another embodiment of a high-power fiber array assembly in which one or more additional cooling channels are positioned above and / or below the fiber end cap 2 to thermally insulate the end cap 2. The additional cooling channels can cool the fiber end cap 2 by receiving light and heat 13 exiting the outer perimeter of the fiber end cap 2. FIG. 7 is a side view in which the optical fibers 1 are arranged in a horizontal plane extending into the page. FIGS. 8 and 9 are two different perspective views of the fiber array assembly without the upper support structure 3b in place. In this embodiment, the front lower cooling channel 11a and the upper cooling channel 11b each have a transverse segment that extends below and above the end cap 2, respectively. In this embodiment, the front lower cooling channel 11a and the upper cooling channel 11b are formed as branches of the lower cooling channel 4a and the upper cooling channel 4b. In an alternative embodiment, the front lower cooling channel 11a and the upper cooling channel 11b are independent of the lower cooling channel 4a and the upper cooling channel 4b and thus have separate amounts of fluid flowing therethrough.

[0027] Figures 10-11 illustrate yet another embodiment of a high-power fiber array assembly in which the lower cooling channel 4a and the upper cooling channel 4b each have a closed-loop cooling channel associated therewith. FIG. 10 shows a side view and FIG. 11 shows an exploded perspective view. As shown, the lower cooling channel 4a is associated with a lower closed-loop cooling channel 16a and the upper cooling channel 4b is associated with an upper closed-loop cooling channel 16b. The lower closed-loop cooling channel 16a and the upper closed-loop cooling channel 16b are located closer to the optical fiber 2 in the radial direction than the lower cooling channel 4a and the upper cooling channel 4b, thereby receiving better the energy generated by the light retroreflected from the fiber end cap 2. In these embodiments employing a transmissive support structure, the lower closed-loop cooling channel 16a and the upper closed-loop cooling channel 16b can include absorption dies for better absorbing the light that enters the support structure 3 and heats the fluid of the closed-loop channel. As indicated by arrow 18 in FIG. 10, the heat from the lower closed-loop cooling channel 16a and the upper closed-loop cooling channel 16b flows respectively into the lower cooling channel 4a and the upper cooling channel 4b, and the heat is removed from the fiber array assembly by the fluid flowing therethrough.

[0028] Figures 12 and 13 illustrate another embodiment of a high-power fiber array assembly in which the cooling conduits are formed from tubes 17a and 17b extending through the support structure 3. FIG. 12 is a side view and FIG. 13 is an exploded perspective view. As shown, the tubes 17a and 17b extend through voids defined by notches 30a and 30b formed in the lower support structure 3a and the upper support structure 3b. In the example shown, the tube 17b extends into the void above the optical fiber array and the tube 17a extends into the void below the optical fiber array.

[0029] Note that the various features of the illustrative embodiments described above can be combined in different embodiments that would be apparent to those skilled in the art. For example, in some embodiments, the high-power fiber array assembly can incorporate cooling conduits formed from channels and tubes. As another example, in some embodiments, the closed-loop cooling channels can be located only in one of the upper or lower support structures, and the other of the upper or lower support structures can include front cooling channels to thermally insulate the end caps. More generally, the number of conduits and the specific configuration of the conduits shown in the depicted embodiments are presented for illustrative purposes only and do not limit the type or kind of conduit arrangement that can be incorporated to remove heat resulting from the light energy that is retroreflected from the end caps and enters the support structure.

[0030] The foregoing description has been presented for purposes of illustration and description with reference to specific embodiments. However, the illustrative embodiments are not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teachings. The embodiments were chosen and described in order to best explain the principles of the embodiments and their practical application, thereby enabling others skilled in the art to best utilize the embodiments and various modifications as are suited to the particular use contemplated. Accordingly, the embodiments are to be regarded as illustrative rather than limiting, and the invention is not to be limited to the details given herein, but may be modified within the scope of the appended claims and their equivalents.

Claims

Claim 1 An optical fiber array assembly for high-power applications, comprising: a support structure; an optical fiber array extending through the support structure and having a plurality of optical fibers extending in a common longitudinal direction; a plurality of end caps, each of the end caps being arranged to be attached to an end portion of one of the optical fibers; a fluid conduit device having one or more conduits extending through the support structure, the one or more conduits being configured to support a flow of fluid therein to remove heat generated from light energy that is retroreflected from the end caps and enters the support structure; The support structure includes upper and lower support structures that fit together with the optical fiber array positioned therebetween, and the upper and lower support structures each include corresponding notches that define a void when the upper and lower support structures are fitted together. An optical fiber array assembly. Claim 2 The optical fiber array assembly according to claim 1, wherein the one or more conduits include at least one channel formed within the support structure. Claim 3 The optical fiber array assembly according to claim 1, wherein the one or more conduits include at least one tube extending through the support structure. Claim 4 The support structure includes a void positioned to receive retroreflected light energy, and the one or more conduits extend across a plurality of optical fibers within the optical fiber array, thereby passing through the sidewalls defining the void. A first conduit having a first conduit segment that receives retroreflected light energy as light and / or heat entering the support structure. The optical fiber array assembly according to claim 1. Claim 5 The optical fiber array assembly according to claim 4, further comprising a second conduit having a second conduit segment that extends across a plurality of optical fibers on a first side of the optical fiber array and across a plurality of optical fibers on a second side of the optical fiber array opposite the first side. Claim 6 The optical fiber array assembly according to claim 5, wherein each of the first and second conduits has an inlet and an outlet through which fluid enters and exits, respectively. Claim 7 The optical fiber array assembly according to claim 4, wherein a side wall of the gap has an absorption coating that absorbs backward-reflected light energy. **Claim 8** The optical fiber array assembly according to claim 1, wherein the support structure transmits backward-reflected light energy, and the fluid flowing in the one or more conduits includes an absorption die that absorbs backward-reflected light energy. **Claim 9** The optical fiber array assembly according to claim 4, further comprising a third conduit segment extending across a plurality of end caps to remove light energy that is backward-reflected from the end caps and enters the support structure from a circumferential side wall of the end caps. **Claim 10** The optical fiber array assembly according to claim 4, further comprising a closed-loop conduit containing a fluid and having an absorption die therein that absorbs backward-reflected light energy, the closed-loop conduit being positioned closer to the optical fiber than the first conduit in a radial direction such that heat absorbed by the closed-loop conduit flows through the support structure to the first conduit. **Claim 11** The optical fiber array assembly according to claim 1, wherein the one or more conduits each include first and second conduits extending into the upper and lower support structures, the first and second conduits being symmetrically arranged relative to each other around a mating surface where the upper and lower support structures contact.

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