Patent Description:
This application is related to <CIT> (and issued as <CIT>).

The field is laser diode beam shaping and combining.

There is a great demand for fiber-coupled high-power, high-brightness diode lasers for applications such as fiber laser pumping and materials processing. In existing fiber-coupled laser diode package devices, multiple single-emitter diode lasers emit respective beams that are stacked in the fast axis to achieve power scaling and brightness improvement. However, additional improvements to brightness are desirable for at least the above mentioned applications.

Prior art publication <CIT> discloses methods, apparatuses and systems for combining and integrating multiple laser beams of a laser diode bar into fewer beams. Embodiments of <CIT> provide a lens (e.g. anamorphic lens) or array of lenses (e.g. an array of anamorphic lenses) to reshape an incident laser beam profile(s) in the fast and slow axis directions into desired laser beam profile(s). A multi-beam integrator system is used along with a means of optically rotating the emitters by an angle (e.g. <NUM> degrees). The angle rotation allows for better balancing of the optical invariants in the slow and fast axis directions, making it easier to "circularize" the image for coupling into fibers or to increase the irradiance for laser machining applications. Moreover, a lens (e.g. anamorphic lens) is used to achieve a nearly circular beam along with providing a significant increase in irradiance.

Publication <CIT> discloses a light generating apparatus that comprises a plurality of laser diode arrays, each array comprising at least one light emitting region adapted for emitting light in a individual beam. The plurality of laser diode arrays are arranged such that light from the individual beams is combined in a combined beam. The arrays define both a fast axis and a slow axis and a lens is further used to collimate light emitted in an individual beam from each laser diode array along a direction of the slow axis.

Publication <CIT> discloses beam compressors that include separated surfaces having positive and negative optical powers. A surface spacing is selected so that a collimated beam input to the beam compressor is output as a collimated beam. The beam compressors are situated to compress a laser beam stack that includes beams associated with a plurality of laser diodes. Beam compression ratios are typically selected so that a compressed beam stack focused into an optical waveguide has a numerical aperture corresponding to the numerical aperture of the optical waveguide.

The invention provides an apparatus according to independent claim <NUM> and a method according to independent claim <NUM>. Further embodiments are provided by the dependent claims.

The foregoing and other objects, features, and advantages of the disclosed technology will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures.

A maximum number of emitter beams that can be coupled into a given fiber is typically ultimately determined by the beam parameter product (BPP) of the single emitter diode lasers used to generate corresponding laser beams. However, to maximize the use of the available brightness of the emitted beams, it can also be important to efficiently arrange the laser diodes both optically and physically so as to fill up the available numerical aperture of the optical fiber in which the beams are coupled. For example, an issue that prevents maintaining single emitter brightness is the typically rectangular beam shape in both physical and angular space and the mismatch with the circular space of the fiber. Thus, in representative examples herein, the circular space of an output fiber is filled through beam shaping of the diode laser beams, thereby allowing more single emitter beams coupled into the same fiber, so that brightness improvement can be achieved.

In various examples herein, high brightness fiber-coupled laser diode packages maximize a laser diode emitter count used to generate corresponding beams that can be coupled into a selected fiber BPP. In one example, a high brightness package includes eighteen emitters operating at <NUM>-nm, with <NUM>-emitters per polarization (x2 polarization multiplexed), providing <NUM>-W of fiber-coupled optical power at <NUM>-nm into a <NUM>-µm, <NUM> NA beam. Such a high brightness package can produce a focused spot with focusing optics at a circular input face <NUM> of an optical fiber, as shown in the optically modeled image in <FIG> shows an optical model image of the same input face <NUM> but instead for a numerical aperture (NA) excitation. Thus, even with efficient vertical stacking of the beams in physical and NA space, further brightness scaling can be achieved by filling in the large "dead space" in the physical and NA space (or image and angle space) due to mismatch between a circular space of the fiber and a rectangular shape of the beams. In various examples herein, beam shaping is applied with beam shaping optics at or before an afocal plane of emitted laser diode beams so as to utilize a more complete space of a circular output fiber (both physical and NA) or other circular output aperture.

In various laser diode package examples, a plurality of laser diodes emit respective laser diode beams typically with asymmetric divergences across perpendicular axes mutually perpendicular to emission axes. The asymmetric divergences are typically associated with the large aspect ratios of the facets of the laser diodes, such that a fast divergence is obtained across the narrower dimension (e.g., an emitter thickness typically corresponding to a growth direction in semiconductor laser diode examples) and a slow divergence is obtained across a wider direction (e.g., a lateral or exit facet width direction). The fast divergence and slow divergence can be defined along respective perpendicular axes which can be referred to as fast axes and slow axes. After beam shaping, the beams are imaged at an output aperture, such as a fiber aperture. The fast axis and slow axis image spot sizes of a diode laser beam i at the fiber aperture can be approximately expressed as, respectively, <MAT> <MAT> where BFA and BSA are the diode beam size (near field) in the fast and slow axis, fO, fFAC and fSAC are the focal length of the objective lens, fast axis collimator (FAC), and SAC lens, and MFAT and MSAT are the magnifications of the fast axis telescope (FAT) and slow axis telescope (SAT), respectively. In the laser diode package example shown in <FIG>, the diodes, including their beam sizes, and the powers of the optics are the same for each diode beam, and therefore produce an approximately same image spot size at the fiber aperture. The images of all the diode laser beams therefore overlap with each other after focusing, as shown in the ensemble image in <FIG>. An ensemble fast axis NA of the beam stack and a slow axis NA of the diode laser beam i, respectively, is approximately: <MAT> <MAT> where dstair is a diode laser stair height (e.g., a physical vertical spacing between adjacent diode laser beam axes as emitted from respective laser diodes), and <MAT> is a slow axis full width divergence angle of each laser diode beam.

Specifically, the ensemble NA excitation shown in <FIG> includes nine diode beams per polarization stacked in vertical direction (two polarizations overlapping each other), with each beam having the same slow axis NA, and the fast axis NA being defined by the sum of the associated stair heights.

In representative examples, the circular space of the fiber is filled through beam shaping, such that different beams in the vertical stack are shaped differently. For example, diode beams near the center of the vertical beam stack are shaped in the slow axis direction to have larger slow axis NA than diode beams near the edge of the beam stack. Because of the conservation of the slow axis BPP, the slow axis image spot size at the fiber input for the beams near the center is smaller than that for beams near the edge of the beam stack. The corresponding beams are also shaped in the fast axis, but in the opposite direction as for slow axis. For example, beams near the center of the vertical stack are shaped to have smaller fast axis NA than beams near the edge. Similarly, the fast axis image spot size at the fiber input for the beams near the center is larger than those near the edge. The beam shaping in both axes are selected so that the spot of each beam fills up the fiber core equivalently or approximately equivalently, even though the aspect ratios between the fast and slow axis image spot sizes are different between beams. In some examples, the beam shaping can reduce an ensemble fast axis NA. In some examples, the beam examples can allow stacking additional diode laser emitters per polarization within the same fast axis NA.

<FIG> plot the modeled spot and NA excitation at the input of a <NUM> fiber and <NUM> NA, according to some brightness enhancing examples herein that use beam shaping. As a way of contrasting, the same diodes as used in the package shown in <FIG> are used in <FIG>. However, beams from a total of eleven emitters per polarization can be coupled in an input face <NUM> of an optical fiber, with the same fiber coupling efficiency and NA excitation (><NUM>% fiber coupling efficiency and ><NUM>% power enclosure within <NUM> NA). The fiber coupled power and brightness of the package is <NUM>% higher than that shown in <FIG> due to the two additional coupled diode beams per polarization. As shown in <FIG>, the physical spot and NA of the beam stack is effectively circularized to an extent, better filling up the circular space of the fiber in both physical and NA space.

<FIG> illustrates the different beams in a vertical beam stack <NUM> being shaped differently, according to a representative beam shaping example. For the three beams 302e, 302f, <NUM> near the center of the beam stack, the image spot <NUM> is elongated in the fast axis and compressed in the slow axis. This corresponds to an increased NA in the slow axis but a reduced NA in the fast axis for the beams 302e-<NUM>. For the beam 302a near the edge of the beam stack <NUM>, the image spot <NUM> is elongated in the slow axis and compressed in the fast axis, resulting in an increased NA in the fast axis and reduced NA in the slow axis. Image space images <NUM>, <NUM>, <NUM> for the beams 302b, 302c, 302d between the center beams 302e-<NUM> and the edge beam <NUM> show a gradual change in aspect ratio according to beam position. By using beam shaping optics, such as according to examples herein, the circular space, both physical and NA, of the fiber can be more completely filled, to allow additional beams/diodes coupled into the same fiber per polarization. While eleven beams are shown in <FIG>, it will be appreciated that any number of beams and emitters may be used that may be coupled into an optical fiber, and any desired beam multiplexing scheme may be optionally used.

Various configurations of beam shaping optics can be used alone or combined with each other to circularize an ensemble image space and NA space of a collection of laser diode beams emitted from respective laser diodes. For example, one or more of the beam specific variables (with superscript i) in Eq. (<NUM>), (<NUM>), (<NUM>) and (<NUM>) above can be varied for shaping the image spot size and NA of individual beams in the vertical beam stack, to reduce the ensemble fast axis NA in Eq. (<NUM>).

In some examples, various FAC lens can be used with different corresponding focal lengths, <MAT>, and various SAC lens can be used with different corresponding focal lengths, <MAT>, for different beams. In some of such examples, various stair heights, <MAT>, can be selected to match the FAC lens focal length (e.g., a smaller stair height can be selected to match a longer focal length FAC lens, and vice versa), while maintaining the other variables, such as), <MAT> and <MAT> constant among different beams. For example, the FAC (SAC) focal lengths for the beams near the center of the vertical beam stack can be shorter (longer) than those for the beams near the edge of the stack. According to Eq. (<NUM>), (<NUM>) and (<NUM>), this leads to a larger (smaller) image spot size, <MAT> ( <MAT>) in the fast (slow) axis for the center beams than the edge beams, and larger slow-axis NA, <MAT> for the center beams. The stair height for each beam can be matched to the FAC lens focal length, leading to a smaller ensemble fast axis NA, <MAT>, according to Eq. (<NUM>). In further embodiments, a fast axis telescope beam compressor is used to vary a relative beam spacing in the fast axis.

In further embodiments, a variable magnification fast axis telescope (VFAT) cis used to produce a variable magnification and relative fast axis beam spacing <MAT>, while allowing the convenient option in many examples of maintaining other variables constant or even among different beams (such as FAC lens focal lengths, stair heights, and SAT magnification <MAT>). Examples of suitable VFATs are disclosed in the related provisional application <CIT> and hereinbelow. VFATs can be <NUM>-piece optics, such as the VFAT example <NUM> shown in <FIG>, or multiple lenses or lens elements. VFAT examples can be configured to provide variable magnification of a collimated beam depending on a transverse position of the beam relative to an optical axis of the VFAT. In specific examples, VFATs produce a lower magnification to the beams incident near the center of the beam stack, so as to produce a larger fast axis image spot size, <MAT> for the center beams than the edge beams. <FIG> also shows the magnification of a FAT without a variable magnification, which has effectively an approximately constant magnification across the transverse direction of the optical axis. <FIG> shows an example laser diode package (with a lid removed) that combines beams of two different laser diode sub-assemblies <NUM>, <NUM> using a polarization multiplexer assembly including a half-wave plate <NUM>, prism surface <NUM>, and polarizing beam splitter <NUM>. In examples herein, a fast axis telescope <NUM> can be configured as a VFAT. The variably magnified beams are then focused with focusing optic <NUM> to a coupling plane of an optical fiber. It will be appreciated that the emitter and beam combining arrangement disclosed in <FIG> is only an illustrative example, not being exhaustive or limiting, and that numerous other laser diode package configurations may be used.

In some VFAT examples, various SAC lenses can be used with different corresponding SAC lens focal lengths, <MAT>, for different beams. An example with specific SAC lenses with various focal lengths can be seen in <FIG>. In the specific example, the focal lengths for the different SACs vary from <NUM> for the center beam to <NUM> for the edge beam though it will be appreciated that various values may be used depending on the package, diode, and other optical characteristics. Turning mirrors are used to direct the beams into a vertical stack. With the variable focal lengths for the SACs, a smaller slow axis image spot size, <MAT>, is obtained at the fiber for the center beams than the edge beams, and larger slow-axis NA, <MAT> is obtained for the center beams. According to Eq. (<NUM>), the arrangement of variable magnification <MAT> leads to a reduced ensemble fast axis NA without the need to change the stair heights.

In further VFAT examples, various slow axis diode beam sizes (near fields), <MAT>, can be provided for different beams in the vertical beam stack, while in some examples maintaining the other variables among different beams constant in Eq. (<NUM>) to (<NUM>). For example, the slow axis beam size variation can be achieved on chip in the diode laser single emitters with different waveguide characteristics such as waveguide dimension, such as using flared laser oscillator waveguides (FLOW) with various near fields, other than obtained optically. Specifically, a smaller slow axis beam size for diodes near the center of the beam stack can allow for a smaller slow axis image spot size, <MAT>. Assuming a fixed BPP for each diode laser single emitter, slow axis full width divergence angle, <MAT>, is inversely proportional to the slow axis beam size, resulting in a larger slow axis NA, <MAT>, according to Eq. (<NUM>). Again, the VFAT allows a larger fast axis image spot size, <MAT> for the center beams than the edge beams. According to Eq. (<NUM>), such arrangement of variable magnification <MAT>, can lead to a reduced ensemble fast axis NA at a coupling plane without the need to change the stair heights.

In additional examples, a VFAT can be used to provide variable fast axis magnification and beam displacement, and two-lens SAC pairs can be used for each beam. In some SAC pair examples, such as the beam shaping optics arrangement <NUM> shown in <FIG>, two SAC lenses 502a-<NUM>, 504a-<NUM> per beam 506a-<NUM> of the same focal lengths are used, with various slow axis focal lengths achieved through varying the separation between the two lenses and displacement of the two lenses from the diodes emitting the beams. That is, each of the plano-concave first SAC elements 502a-<NUM> can have a common focal length, and each of the plano-convex second SAC elements 504a-<NUM> can have a common focal length. A VFAT and focusing optics <NUM> can then receive the beams and form a circularized beam ensemble at a coupling or focusing plane <NUM>, which can correspond to a an optical fiber input face, a relay system, etc. In additional SAC pair examples, such as that shown in <FIG>, a first SAC lens for each diode of one half of a stack has a different focal length, and a common second SAC lens, such as the dashed lens element <NUM> in <FIG>, can be placed in the afocal plane to provide optical power on all beams in the beam stack. The beams after the first SAC lenses (which can be plano-convex, plano-concave, etc.) are not slow-axis collimated, but become collimated in the slow axis after the second common SAC lens. This allows working distances of the first SAC lenses that are different from ones shown on the right of <FIG>, and can allow a shorter spacing for a smaller laser diode package form factor or volume.

In further examples, a variable magnification fast axis telescope (VFAT) <MAT> can be used along with a variable magnification slow axis telescope (VSAT) <MAT> while maintaining the other variables, such as <MAT> and <MAT> constant among different beams. Variation of the VFAT and VSAT is along the transverse direction, such that different magnification for different beams in the vertical stack are provided for both the slow axes and fast axes. Examples can include arrangements with separate telescopes, such as one VFAT and one VSAT, but could also be one telescope that implements the variable magnification for both axes.

In general, examples herein can more efficiently fill a circular space of a coupling plane, such as a fiber, both physical and NA, through beam shaping of the diode laser beams, so as to allow more single emitters to generate beams for coupling into the same fiber, so that brightness improvement is achieved. While example brightness improvements of <NUM>% are shown, higher improvements can be achieved as well, including as high as <NUM>% power and brightness improvement in some examples where all the "dead space" in the physical and NA space due to mismatch between a circular space of the fiber and rectangular beam shape becomes filled, where <NUM>% is the additional area in a circle over a rectangle having the same length of diameter and diagonal, respectively.

As discussed above, laser diode packages typically couple laser diode beams emitted from rectangular diode facets into a circular fibers. This leads to unused spatial and angular laser properties associated with laser diode ensembles optically and physically arranged for fiber coupling at ensemble coupling planes (such as fiber input faces). There is a significant problem associated with the laser diodes' rectangular high aspect ratio in both physical and angular space and the mismatch with the circular space of the fiber. The circular spaces of the fiber can be more completely filled by varying laser diode chip geometries or varying FAC lenses for different laser diodes but such approaches are not typically cost effective.

By using one or more variable afocal telescope examples described herein, channel specific optics or layouts can be reduced or avoided, by providing variable magnification of a collimated beam. When applied to a laser diode package to angularly and spatially circularize its aggregate beam, individual diode channels can receive specific different magnifications based on, for example, their particular NA space juxtaposition or arrangement. This varying magnification varies their vertical physical dimension at focus, which can allow a net higher compression of the aggregate beam space so that, for example, additional laser channels can be added within the same NA of the fiber input.

Monolithic telescope optics typically provide a single-magnification ratio associated with surfaces of differing but constant curvatures. Alternatively, the surfaces are made aspheric to reduce spherical aberration across its clear aperture. In some examples herein, a variable magnification can be provided with a variable afocal telescope, allowing an increase of output brilliance (i.e., radiance) by up to <NUM>% in various laser diode packages examples. For example, a fiber-coupled laser diode package that uses eighteen single-emitter laser diodes to generate beams and optics to couple the beams into a <NUM> NA <NUM> output fiber can instead use twenty-two single-emitter laser diodes of the same type to generate beams and use optics (including the variable afocal telescope) to couple the beams into the same <NUM> NA <NUM> output fiber.

<FIG> shows a physical form factor and surface shape for an example afocal telescope <NUM>. The afocal telescope <NUM> includes a transmissive optical substrate <NUM> having a first surface <NUM> that is convex and a second surface <NUM> that is concave, each having respective curvatures defined thereon. The transmissive optical substrate <NUM> can be made of different materials, or have portions with different materials, including glasses, plastics, fused silica, transparent crystalline or non-crystalline materials. The curvatures for the first and second surfaces <NUM>, <NUM> can be symmetric across an optical axis <NUM> of the afocal telescope <NUM> in the plane of <FIG>. In representative examples, the afocal telescope <NUM> is a unitary cylindrical meniscus lens, with the cylindricity associated with a lack of a rotational symmetry about the optical axis <NUM> (such as with a spherical lens) rather than constant curvatures of cylinders. In additional examples, separate lens elements spaced apart from each other can be used to form a non-unitary lens or separate lens elements can be joined together to form a unitary lens having a plurality of elements. One or both of the first and second surfaces <NUM>, <NUM> can have a hyperbolic shape. As shown, the first surface <NUM> has a parabolic shape and the second surface <NUM> has a hyperbolic shape. The shapes can define higher curvature pairs (magnification) near the center (e.g., closer to the optical axis <NUM>) and more gradual curvatures near the edges of aperture of the afocal telescope <NUM>. In further examples, afocal telescopes can be configured to provide variable slow axis magnifications or can have complex shapes configured to provide both variable fast and slow axis magnifications.

<FIG> also shows a plurality of input beam axes 708a-<NUM> that are parallel to each other and parallel to the optical axis <NUM>. Each of the input beam axes 708a-<NUM> can be associated with a laser diode beam that is collimated in both a fast axis dimension and a slow axis dimension. With the adjacent arranged parallel input beam axes 708a-<NUM>, the afocal telescope <NUM> is configured as a fast axis telescope such that a common fast axis of the laser diode beams generally extends perpendicular to the optical axis <NUM> in the plane of <FIG> (e.g., up and down). Following the ray trace, the laser diode beams propagate through the substrate <NUM> and become compressed to propagate along output beam axes 710a-<NUM>, with the distance between the two outer output beam axes 710a, <NUM> being shorter than the distance between the two outer input beam axes 708a, <NUM>.

As shown, the input beam axes <NUM>-<NUM> have displacements from each other forming an even spacing. In representative examples, based on the selected curvatures of the first and second surfaces <NUM>, <NUM>, the compressed output beam axes 710a-<NUM> are not evenly spaced. Instead, as the displacement distance from the optical axis <NUM> increases, adjacent output beam axes are increasingly displaced from each other, so that displacement between output beam axes 710e, 710f is smaller than the displacement between output beam axes 710d, 710e, which is smaller than the displacement between output beam axes 710c, 710d, which is smaller than the displacement between output beam axes 710b, 710c, which is smaller than the displacement between output beam axes 710a, 710b, etc. Thus, a linear input spacing can produce a variable output spacing, such that a linearly increasing (e.g., an even spacing) input beam displacement from the optical axis <NUM> produces a nonlinear increase in output beam displacement. Based on the curvature symmetries across the optical axis <NUM>, a similar effect is achieved below the optical axis <NUM> in <FIG>, so that displacement between output beam axes <NUM>, <NUM> is smaller than the displacement between output beam axes <NUM>, 710i, which is smaller than the displacement between output beam axes 710i, 710j, which is smaller than the displacement between output beam axes 710j, <NUM>, etc..

In representative examples, for laser diode beams propagating along the input beam axes 708a-<NUM> with a common cross-sectional shape (e.g., each having identical area and aspect ratio), the afocal telescope <NUM> introduces a variable magnification for the laser diode beams propagating along the output beam axes 710a-<NUM> that is dependent on the displacement distance of the respective input beam axes 708a-<NUM> from the optical axis <NUM>. For example, with reference to <FIG>, the variable magnification can be produced as shown and discussed previously, such that for an increasing distance from the optical axis <NUM>, a magnification increases for a transmitted laser diode beam. For comparison, the magnification line showing the approximately flat magnification of an afocal telescope does not provide a variable magnification. Thus, the laser diode beams propagating along input beam axes 708a, <NUM> are compressed in the fast axis direction by a smaller amount than the laser diode beams propagating along input beam axes 708f, <NUM>. The reduced compression for laser diode beams propagating along input beam axes 708a, <NUM> produces a smaller spot size in physical space in the fast axis direction at a subsequent coupling plane (such as an optical fiber) after propagation through an objective lens. In contrast, the increased compression for laser diode beams propagating along input beam axes 708f, <NUM> produces a larger spot size in physical space in the fast axis direction at the subsequent coupling plane after propagation through the objective lens. By selecting slow axis magnification separately, the laser diode beams propagating along input beam axes 708f, <NUM> can have the larger fast axis image dimension at the coupling plane and a smaller slow axis image dimension at the coupling plane, and the laser diode beams propagating along input beam axes 708a, <NUM> can have the smaller fast axis image dimension at the coupling plane and a larger slow axis image dimension at the coupling plane. A resulting ensemble or aggregate beam image in physical space is shown in <FIG>. The different aspect ratios for the different laser diode beams are imaged on the fiber to produce a circularized ensemble image in physical space. As discussed hereinabove, <FIG> shows an example of an ensemble beam image in which beams do not propagate through an afocal telescope providing variable magnification, resulting in a square shaped image as each beam images a common overlapping area. By introducing the variable spacing and variable magnification among the output beam axes 710a-<NUM> with the afocal telescope <NUM>, additional laser diode beams can be focused at the coupling plane, increasing coupled brightness.

<FIG> shows another example of an afocal telescope <NUM> configured to provide variable magnification, with <FIG> including the sag equation and suitable coefficients for surfaces S1, S2. The coefficients generally define the surface S1 as a parabolic or elliptical with k being close to -<NUM>, and the surface S2 as a hyperboloid with k < -<NUM>. As shown, the afocal telescope <NUM> includes a flat reference surface <NUM>, which can be used to register the afocal telescope <NUM> to a base of a laser diode package housing so as to improve alignability with a plurality of laser diode beams directed through an interior of the laser diode package.

As used in this application and in the claims, the singular forms "a," "an," and "the" include the plural forms unless the context clearly dictates otherwise. Additionally, the term "includes" means "comprises. " Further, the term "coupled" does not exclude the presence of intermediate elements between the coupled items.

The systems, apparatus, and methods described herein should not be construed as limiting in any way. Instead, the present disclosure is directed toward all novel and non-obvious features and aspects of the various disclosed embodiments, alone and in various combinations and subcombinations with one another. The disclosed systems, methods, and apparatus are not limited to any specific aspect or feature or combinations thereof, nor do the disclosed systems, methods, and apparatus require that any one or more specific advantages be present or problems be solved. Any theories of operation are to facilitate explanation, but the disclosed systems, methods, and apparatus are not limited to such theories of operation.

Although the operations of some of the disclosed methods are described in a particular, sequential order for convenient presentation, it should be understood that this manner of description encompasses rearrangement, unless a particular ordering is required by specific language set forth below. Moreover, for the sake of simplicity, the attached figures may not show the various ways in which the disclosed systems, methods, and apparatus can be used in conjunction with other systems, methods, and apparatus. Additionally, the description sometimes uses terms like "produce" and "provide" to describe the disclosed methods. The actual operations that correspond to these terms will vary depending on the implementation and are readily discernible by one of ordinary skill in the art.

In some examples, values, procedures, or apparatus' are referred to as "lowest", "best", "minimum," or the like. It will be appreciated that such descriptions are intended to indicate that a selection among many used functional alternatives can be made, and such selections need not be better, smaller, or otherwise preferable to other selections. Examples are described with reference to directions indicated as "above," "below," "upper," "lower," and the like. These terms are used for convenient description, but do not imply any particular spatial orientation.

Theories of operation, scientific principles, or other theoretical descriptions presented herein in reference to the apparatus or methods of this disclosure have been provided for the purposes of better understanding and are not intended to be limiting in scope. The apparatus and methods in the appended claims are not limited to those apparatus and methods which function in the manner described by such theories of operation.

Claim 1:
An apparatus, comprising:
a plurality of laser diodes configured to emit respective laser diode beams having perpendicular fast and slow beam divergence axes mutually perpendicular to respective beam axes (708a-k); and
beam shaping optics configured to receive the laser diode beams and to circularize an ensemble image space and numerical aperture, NA,
space of the laser diode beams at an ensemble coupling plane; wherein the beam shaping optics comprise:
an afocal fast axis telescope (<NUM>) configured to receive the laser diode beams as fast-axis and slow-axis collimated beams with the beam axes parallel to each other and stacked along a common fast axis to define a plurality of initial beam displacements relative to an optical axis (<NUM>) of the afocal fast axis telescope, and to compress the laser diode beams along the common fast axis such that, for a linear increase in input beam displacement from the optical axis (<NUM>), the afocal fast axis telescope produces an increasing fast-axis compressed beam magnification and a nonlinear increase in a compressed beam displacement from the optical axis (<NUM>).