Abstract
In various embodiments, laser resonator modules produce output beams via manipulation of input beams on opposite sides of the module. The input beams are emitted by one or more beam emitters that may be cooled using a liquid coolant cavity. The liquid coolant cavity may be isolated from optical elements utilized to manipulate the input beams, at least in part, by an isolation wall protruding from the base plate of the resonator module.
Claims
1.-24. (canceled)
25. A laser resonator comprising: a base plate having a first side and a second side opposite the first side; disposed on the first side of the base plate, (i) a mounting area configured to receive a plurality of beam emitters, and (ii) a first optical cavity for manipulation of beams emitted by the beam emitters; and a second optical cavity disposed on the second side of the base plate, wherein the base plate defines an opening therethrough, and the second optical cavity is configured to receive beams from the first optical cavity through the opening.
26. The laser resonator of claim 25, further comprising the plurality of beam emitters received within the mounting area.
27. The laser resonator of claim 26, wherein at least one of the beam emitters is a diode bar configured to emit a plurality of discrete beams.
28. The laser resonator of claim 25, further comprising one or more first optical elements disposed within the first optical cavity.
29. The laser resonator of claim 28, wherein the one or more first optical elements comprise a plurality of collimation lenses and/or a plurality of reflectors.
30. The laser resonator of claim 28, wherein the one or more first optical elements comprise a plurality of slow-axis collimation lenses and a plurality of interleaver mirrors.
31. The laser resonator of claim 28, wherein the one or more first optical elements comprise one or more folding mirrors.
32. The laser resonator of claim 25, further comprising one or more second optical elements disposed within the second optical cavity.
33. The laser resonator of claim 32, wherein the one or more second optical elements comprise (i) a dispersive element for combining a plurality of beams into a multi-wavelength beam, and (ii) a partially reflective output coupler for receiving the multi-wavelength beam from the dispersive element, transmitting a first portion of the multi-wavelength beam as an output beam, and reflecting a second portion of the multi-wavelength beam back toward the dispersive element.
34. The laser resonator of claim 33, wherein the dispersive element comprises a diffraction grating.
35. The laser resonator of claim 33, further comprising a beam output for outputting the output beam.
36. The laser resonator of claim 35, wherein the beam output comprises a window or a coupler configured to connect to an optical fiber.
37. The laser resonator of claim 32, wherein the one or more second optical elements comprise one or more folding mirrors.
38. The laser resonator of claim 25, further comprising a beam output for outputting one or more beams manipulated within the first optical cavity and/or the second optical cavity.
39. The laser resonator of claim 38, wherein the beam output comprises a window or a coupler configured to connect to an optical fiber.
40. The laser resonator of claim 25, further comprising: a liquid coolant cavity disposed beneath the mounting area and configured to receive liquid coolant therewithin; a fluid inlet for supplying the liquid coolant to the liquid coolant cavity; and a fluid outlet for receiving the liquid coolant from the liquid coolant cavity.
41. The laser resonator of claim 40, further comprising a fluid reservoir configured to fit within the liquid coolant cavity and contain the liquid coolant.
42. The laser resonator of claim 40, further comprising an isolation wall extending from the base plate and disposed between the liquid coolant cavity and the second optical cavity.
43. The laser resonator of claim 42, wherein the isolation wall comprises a first material, the base plate comprises a second material, and the first and second materials are the same.
44. The laser resonator of claim 42, wherein the isolation wall comprises a first material, the base plate comprises a second material, and the first and second materials are different.
45.-63. (canceled)
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] In the drawings, like reference characters generally refer to the same parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments of the present invention are described with reference to the following drawings, in which:
[0030] FIG. 1A is a schematic view of a first side of a laser resonator in accordance with various embodiments of the invention;
[0031] FIG. 1B is a schematic view of a second side of a laser resonator in accordance with various embodiments of the invention;
[0032] FIG. 1C is a schematic view of the first side of the laser resonator of FIG. 1A with a cover plate in place in accordance with various embodiments of the invention;
[0033] FIG. 1D is a schematic view of the second side of the laser resonator of FIG. 1B with a cover plate in place in accordance with various embodiments of the invention;
[0034] FIG. 2 is a schematic cross-sectional view of a laser resonator in accordance with various embodiments of the invention;
[0035] FIG. 3 is a schematic view of components of a wavelength beam combining laser system that may be incorporated into a laser resonator in accordance with various embodiments of the invention;
[0036] FIG. 4A is a schematic view of a first side of a laser resonator in accordance with various embodiments of the invention; and
[0037] FIG. 4B is a schematic view of a second side of a laser resonator in accordance with various embodiments of the invention.
DETAILED DESCRIPTION
[0038] FIGS. 1A and 1B schematically depict opposing sides of a laser resonator 100 in accordance with embodiments of the present invention. As shown in FIG. 1A, a first side 105 of the resonator 100 features an optical cavity 110 within which one or more optical elements (e.g., mirrors, prisms, lenses, etc.) are utilized to manipulate laser beams emitted by one or more (typically a plurality of) beam emitters. Also on side 105 is a mounting area 115 for the beam emitters. As best observed in FIG. 2, the optical cavity 110 and mounting area 115 are supported by and separated from the second side of the beam emitter by a base plate that extends across the resonator 100. The optical cavity 110 and mounting area 115 are surrounded by a protruding external wall 120 that may define a plurality of apertures 125 that may be utilized to help seal the optical cavity 110 and mounting area 115 along a sealing path 130. For example, as shown in FIG. 1C, one or more cover plates 132 may be disposed over side 105 and may be fastened to resonator 100 via fasteners (e.g., screws, bolts, rivets, etc.) that extend into (and may mechanically engage with, e.g., threadingly engage with) apertures 125. In other embodiments, the cover plate(s) may be sealed along the sealing path 130 via a technique such as welding, brazing, or use of an adhesive material. FIG. 1A depicts an example embodiment of side 105 without cover plate(s) in place, while FIG. 1C depicts an example embodiment of side 105 with a single cover plate 132 in place and sealing the optical cavity 110 and mounting area 115.
[0039] As shown in FIG. 1B, a second side 135 of the resonator 100 features an optical cavity 140 within which one or more optical elements (e.g., mirrors, prisms, lenses, etc.) are utilized to manipulate laser beams emitted by one or more (typically a plurality of) beam emitters. In various embodiments, as detailed below with reference to FIGS. 4A and 4B, the optical cavities 110, 140 may be portions of the same, larger optical cavity, e.g., an external lasing cavity, and the beams may travel from optical cavity 110 to optical cavity 140 via one or more apertures defined through the base plate of the resonator 100.
[0040] Also on side 135 is a liquid coolant cavity 145. The liquid coolant cavity 145 is, in various embodiments, a hollow cavity configured to contain liquid coolant (e.g., water, glycol, or other heat-transfer fluid) directly beneath the mounting area 115. As shown, the liquid coolant may flow into and out of the cavity 145 via a fluid inlet 150 and a fluid outlet 155, which may be fluidly coupled to, e.g., a reservoir of coolant and/or a heat exchanger for cooling fluid heated by the beam emitters. As detailed in the '134 application, embodiments of the invention may feature a control system that controls the rate of fluid flow into and out of the cavity 145 based on one or more sensed characteristics, e.g., temperature of the beam emitters, the cooling fluid, and/or one or more other components of and/or positions within resonator 100.
[0041] Separating the optical cavity 140 from the liquid coolant cavity 145 is an isolation wall 160 extending from the base plate of the resonator 100. In FIG. 1B, the isolation wall 160 is depicted as surrounding the entirety of the optical cavity 140, but in other embodiments of the invention the isolation wall 160 may be disposed only directly between the optical cavity 140 and the liquid coolant cavity 145. As with side 105, the optical cavity 140 and liquid coolant cavity 145 are surrounded by the protruding external wall 120. In various embodiments, the isolation wall 160 extends along one or more sides of the liquid coolant cavity 145, in order to seal the liquid coolant cavity 145 away from the optical cavity 140. In various embodiments, the isolation wall 160 and the external wall 120 collectively entirely surround the liquid coolant cavity 145; that is, the isolation wall 160 may extend along one or more sides of the liquid coolant cavity 145 that are not adjacent to the external wall 120. In the exemplary embodiment depicted in FIG. 1B, the external wall 120 extends along two adjoining sides of the liquid coolant cavity 145 while the isolation wall 160 extends along the other two adjacent sides.
[0042] A sealing path 165 may be defined around the optical cavity 140 and may, in various embodiments, correspond at least in part to the location of the isolation wall 160. In various embodiments, and as shown in FIG. 1D, a cover plate 162 may be disposed over side 135 and may be fastened to resonator 100 via fasteners (e.g., screws, bolts, rivets, etc.) that extend into (and may mechanically engage with, e.g., threadingly engage with) apertures 125. In other embodiments, the cover plate 162 may be sealed along the sealing path 165 via a technique such as welding, brazing, or use of an adhesive material. In various embodiments, and as shown in FIG. 1D, the optical cavity 140 may be sealed without sealing or covering of the optical coolant cavity 145 (which, then, in various embodiments may house an enclosed reservoir for containing liquid coolant), thereby leaving the optical coolant cavity 145 accessible (e.g., for service, maintenance, or cleaning) without the need to unseal or expose the more delicate components disposed within the optical cavity 140. In other embodiments, the cover plate 162 (or two or more cover plates) may be used to cover and/or seal the entire side 135 of the resonator 100, including the optical coolant cavity 145. For example, in various embodiments, cover plate 162 may cover the optical cavity 140 as shown in FIG. 1D, while a second cover plate may be utilized to cover the optical coolant cavity 145.
[0043] FIG. 2 is a schematic cross-sectional view of the resonator 100, depicting sides 105, 135 of the resonator 100 separated by base plate 200. As shown, the thickness of the base plate 200 in the region directly below the optical cavity 140 may be substantially constant. For example, in various embodiments the thickness of the base plate 200 in the region directly below the optical cavity 140 may range from approximately 5 mm to approximately 35 mm, or even from approximately 5 mm to approximately 50 mm. In various embodiments, the thickness of the base plate 200 in the region directly below the optical cavity 140 may depend upon the overall size of the resonator 100, e.g., the thickness may increase with increasing resonator size. In the region between the mounting area 115 and the liquid coolant cavity 145, the thickness of the base plate 200 may be considerably smaller, in order to enable the liquid coolant to more effectively conduct heat away from the mounting area 115. For example, the thickness of the base plate 200 in the region between the mounting area 115 and the liquid coolant cavity 145 may range from approximately 0.5 mm to approximately 3 mm.
[0044] As shown in FIG. 2, the isolation wall 160 separates the liquid coolant cavity 145 from the optical cavity 140 and provides additional mechanical stability to the resonator 100. As shown, the height of the isolation wall 160 may be approximately equal to the depth of the optical cavity 140 and/or the height of the portion of the external wall 120 that extends beyond the base plate 200. In various embodiments, this height may range from approximately 5 mm to approximately 150 mm, depending upon the size of the resonator 100. (Thus, the total “height” or thickness of the external wall 120 may range from approximately 10 mm to approximately 300 mm.)
[0045] The thickness (i.e., the horizontal dimension in FIG. 2) of the isolation wall 160 and/or of the external wall 120 may range from approximately 1 mm to approximately 75 mm. As shown in FIG. 2, the thickness of the isolation wall 160 may be less than the thickness of the external wall 120. In various embodiments, the thickness of the isolation wall 160 may range from approximately 50% to approximately 75% of the thickness of the external wall 120. In other embodiments, the thickness of the isolation wall 160 may be approximately equal to the thickness of the external wall 120. In various embodiments, the ratio of the thickness of the isolation wall 160 to the thickness of the external wall 120 may range from approximately 0.5 to approximately 1.5. As mentioned above, the presence of the isolation wall 160 may enable the thickness of the base plate 200 to be reduced without significantly compromising the mechanical stability of the resonator 100.
[0046] During operation of the beam emitters in mounting area 115 (e.g., during operation and/or testing of the resonator 100), heat produced thereby may heat the base plate 200 (and/or one or more other portions of the resonator 100), resulting in thermal expansion thereof. Such thermal expansion may tend to produce a bending force on the resonator 100 that tends to bend side 105 outward and, correspondingly, side 135 inward. In various embodiments, the isolation wall 160 resists such bending forces, minimizing or substantially preventing deformation and/or bending of the resonator 100 (e.g., the base plate 200). In this manner, the precise optical alignment of the various optical elements within the optical cavities 110, 140 is maintained, even during operation of the beam emitters.
[0047] In various embodiments, the isolation wall 160, base plate 200, and external wall 120 (and/or cover plates configured to cover optical cavities 110, 140) may include, consist essentially of, or consist of one or more rigid materials, e.g., stainless steel, copper, magnesium, and/or aluminum. In various embodiments of the invention, such rigid materials may have a Young's modulus ranging from approximately 30 GPa to approximately 450 GPa, or even larger. The use of stronger, more rigid materials may enable the use of designs having smaller thicknesses, while the use of less rigid materials may require one or more thicker components. As shown in FIG. 2, the isolation wall 160 may protrude upward from the base plate 200 and may include, consist essentially of, or consist of a portion of the same material of the base plate 200. That is, a solid piece of material may be machined or otherwise shaped to define the shapes of the base plate 200, the external wall 120, and the isolation wall 160. In other embodiments, the isolation wall 160 may include, consist essentially of, or consist of a material different from that of the base plate 200 and/or may be attached to the base plate 200 via, e.g., welding, brazing, soldering, or another attachment technique. In various embodiments, since the isolation wall 160 is not exposed to cooling fluid during typical use, the isolation wall 160 need not be substantially corrosion-resistant; rather, the material for isolation wall 160 may be selected to provide mechanical strength even at small thicknesses.
[0048] While in FIG. 2 the thickness of the isolation wall 160 is depicted as being approximately constant along the entire height of isolation wall 160, in various other embodiments the thickness of isolation wall 160 may vary along the height of isolation wall 160. For example, the thickness of isolation wall 160 at the interface between isolation wall 160 and base plate 200 may be smaller than or larger than the thickness at the opposing end of isolation wall 160. The thickness of isolation wall 160 may vary gradually over all or a portion of its height, or the thickness may vary in one or more discrete steps along the height of the isolation wall.
[0049] Resonators in accordance with embodiments of the present invention may be utilized in WBC laser systems. While exemplary embodiments include WBC resonators, embodiments of the invention may also be utilized with other types of laser resonators utilizing one or more beam emitters. FIG. 3 schematically depicts various components of a WBC resonator 300 that may be utilized in embodiments of the present invention. In the depicted embodiment, resonator 300 combines the beams emitted by nine different diode bars (as utilized herein, “diode bar” refers to any multi-beam emitter, i.e., an emitter from which multiple beams are emitted from a single package). Embodiments of the invention may be utilized with fewer or more than nine emitters. In accordance with embodiments of the invention, each emitter may emit a single beam, or, each of the emitters may emit multiple beams. The view of FIG. 3 is along the WBC dimension, i.e., the dimension in which the beams from the bars are combined. The exemplary resonator 300 features nine diode bars 305, and each diode bar 305 includes, consists essentially of, or consists of an array (e.g., one-dimensional array) of emitters along the WBC dimension. In various embodiments, each emitter of a diode bar 305 emits a non-symmetrical beam having a larger divergence in one direction (known as the “fast axis,” here oriented vertically relative to the WBC dimension) and a smaller divergence in the perpendicular direction (known as the “slow axis,” here along the WBC dimension).
[0050] In various embodiments, each of the diode bars 305 is associated with (e.g., attached or otherwise optically coupled to) a fast-axis collimator (FAC)/optical twister microlens assembly that collimates the fast axis of the emitted beams while rotating the fast and slow axes of the beams by 90°, such that the slow axis of each emitted beam is perpendicular to the WBC dimension downstream of the microlens assembly. The microlens assembly also converges the chief rays of the emitters from each diode bar 305 toward a dispersive element 310. Suitable microlens assemblies are described in U.S. Pat. No. 8,553,327, filed on Mar. 7, 2011, and U.S. Pat. No. 9,746,679, filed on Jun. 8, 2015, the entire disclosure of each of which is hereby incorporated by reference herein.
[0051] In embodiments of the invention in which both a FAC lens and an optical twister (e.g., as a microlens assembly) are associated with each of the beam emitters and/or emitted beams, and slow-axis collimator (SAC) lenses may be utilized to manipulate the beams in the non-WBC dimension. In other embodiments, the emitted beams are not rotated, and FAC lenses may be utilized to manipulate the beams in the non-WBC dimension. Thus, it is understood that references to SAC lenses herein generally refer to lenses having power in the non-WBC dimension, and such lenses may include FAC lenses in various embodiments. Thus, in various embodiments, for example embodiments in which emitted beams are not rotated and/or the fast axes of the beams are in the non-WBC dimension, FAC lenses may be utilized as detailed herein as replacements for SAC lenses, and vice versa.
[0052] As shown in FIG. 3, resonator 300 also features a set of SAC lenses 315, one SAC lens 315 associated with, and receiving beams from, one of the diode bars 305. Each of the SAC lenses 315 collimates the slow axes of the beams emitted from a single diode bar 305. After collimation in the slow axis by the SAC lenses 315, the beams propagate to a set of interleaving mirrors 320, which redirect the beams 325 toward the dispersive element 310. The arrangement of the interleaving mirrors 320 enables the free space between the diode bars 305 (and the beams emitted thereby) to be reduced or minimized. Upstream of the dispersive element 310 (which may include, consist essentially of, or consist of, for example, a diffraction grating such as the transmissive diffraction grating depicted in FIG. 3, or a reflective diffraction grating), a lens 330 may optionally be utilized to collimate the sub-beams (i.e., emitted rays other than the chief rays) from the diode bars 305. In various embodiments, the lens 330 is disposed at an optical distance away from the diode bars 305 that is substantially equal to the focal length of the lens 330. Note that, in typical embodiments, the overlap of the chief rays at the dispersive element 310 is primarily due to the redirection of the interleaving mirrors 320, rather than the focusing power of the lens 330.
[0053] As detailed in U.S. Pat. No. 10,268,043, filed on Jan. 19, 2017 (the '043 patent), the entire disclosure of which is incorporated by reference herein, the dispersive element may include, associated therewith, proximate thereto, or in contact therewith, one or more prisms. That is, references to a dispersive element herein may refer to combinations of, for example, a diffraction grating and one or more prisms. In various embodiments, the one or more prisms may improve WBC beam quality.
[0054] Also depicted in FIG. 3 are lenses 335, 340, which form an optical telescope for mitigation of optical cross-talk, as disclosed in U.S. Pat. No. 9,256,073, filed on Mar. 15, 2013, and U.S. Pat. No. 9,268,142, filed on Jun. 23, 2015, the entire disclosure of each of which is hereby incorporated by reference herein. Resonator 300 may also include one or more optional folding mirrors 345 for redirection of the beams such that the resonator 300 may fit within a smaller physical footprint. The dispersive element 310 combines the beams from the diode bars 305 into a single, multi-wavelength beam 350, which propagates to a partially reflective output coupler 355. The coupler 355 transmits a portion of the beam as the output beam of resonator 300 while reflecting another portion of the beam back to the dispersive element 310 and thence to the diode bars 305 as feedback to stabilize the emission wavelengths of each of the beams. In this manner, an external-cavity lasing system, in which the secondary mirror for each emitter is disposed at a distance away from the emission aperture or facet of the emitter, is formed in resonator 300.
[0055] In various embodiments of the invention, a laser system incorporates multiple resonators 300 each configured as shown for resonator 100, and the output beams from the resonators 300 are combined downstream (e.g., within a housing and/or by one or more optical elements) into a single output beam that may be directed to a workpiece for processing (e.g., welding, cutting, annealing, etc.) and/or coupled into an optical fiber.
[0056] Various embodiments of the invention implement an external cavity laser system on resonator 100 and reduce the required size of resonator 100 by utilizing optical cavities 110, 140 as portions of a larger optical cavity. Reflectors such as mirrors may be utilized to direct the beams within the optical cavity, and, since the optical cavity extends along both sides 105, 135, the overall size of the resonator 100 may be correspondingly reduced for the same cavity size (e.g., compared to a resonator having an optical cavity on only one side). In various embodiments, splitting the optical cavity of the resonator onto both sides of the resonator module may not only reduce the required size of the resonator, but may also reduce deleterious strains and/or deformation due to heat generated by the optical components in the optical cavity. That is, thermal effects are less likely to deform the resonator toward one side or the other since heat may be generated on both sides of the module.
[0057] In an exemplary embodiment, as shown in FIGS. 4A and 4B, beams from beam emitters disposed in mounting area 115 may be focused by a group of lenses (and/or other optical elements; for example, SAC lenses 315) disposed in lens area 400 toward a group of mirrors in a mirror area 405 (which may contain, in various embodiments, interleaver mirrors 320). In various embodiments, the beam emitters may be mounted over the base plate as detailed within, for example, U.S. patent application Ser. No. 16/597,949, filed on Oct. 10, 2019, the entire disclosure of which is incorporated by reference herein. In various embodiments, each beam emitter may be mounted on and thermally coupled to an impingement-style cooling apparatus utilizing cooling fluid from the liquid coolant cavity, for example as described in U.S. patent application Ser. No. 16/654,339, filed on Oct. 16, 2019, the entire disclosure of which is incorporated by reference herein.
[0058] From mirror area 405, the beams from the beam emitters may be directed to another mirror area 410 (containing one or more reflectors such as mirrors, e.g., folding mirrors) and thence through an opening 415 to optical cavity 140 on side 135. Although the example embodiment depicted in FIGS. 4A and 4B features one opening 415, in accordance with various embodiments of the invention, resonators feature two or more openings through the base plate, one or more (or even all) of which may be positioned, shaped, or otherwise configured to enable beams to pass from one side of the resonator to the other. In optical cavity 140, the beams may be directed to a mirror area 420 (containing one or more reflectors such as mirrors, e.g., folding mirrors), which reflects the beams to a beam-combining area 425. In example embodiments, the beam-combining area 425 may include therewithin the diffusive element 310 (and, in some embodiments, the output coupler 355). In various embodiments, the beams each have a different wavelength, and the beams are combined in beam-combining area 425 into an output beam composed of the multiple wavelengths. The beam from the beam-combining area 425 may be directed to a mirror 430 (which, in various embodiments, may be partially reflective output coupler 355) and thence to an output 435 for emission from the resonator 100. For example, the output 435 may be a window for emission of the beam therethrough or an optical coupler configured to connect to an optical fiber. In various embodiments, as detailed in the '728 application, the output 435 may be rotatively adjustable (for example, about a pair of perpendicular coordinate axes that may be parallel to the face or end of the resonator 100).
[0059] The terms and expressions employed herein are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed.
