High Power Laser Diode Packaging

Abstract

A high power laser diode assembly uses a greater number of emitters in a laser diode package, or uses larger, wider laser diode emitters, to produce a higher power laser output. Each assembly design option includes a meniscus slow axis collimator lens having a light incident surface that imparts a strong negative lens surface focal power to cause the incident beam to diverge outward, and a light exit surface that imparts a stronger positive lens surface focal power to collimate the rapidly diverging beam. In one example, a 5 mm focal length meniscus collimator lens can reduce the physical path from the collimator lens to the laser diode by 7 mm compared to a standard 12 mm focal length collimator lens. In another example, a 15 mm focal length meniscus collimator lens has the same back focal length as a standard 12 mm collimator, which can increase the width of the chip on the submount from 200 pm to 250 pm.

Description

[0001] Related Applications

[0002] This application claims the benefit of priority to U.S. Patent Application No. 16 / 192,696, filed on November 15, 2018, which is incorporated herein by reference.

[0003] Copyright Notice

[0004] © 20218nLIGHT, Inc. A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure as it appears in the Patent and Trademark Office patent file or records, but in any event all copyright rights are reserved. 37 CFR §1.71(d). Technical Field

[0005] The present disclosure relates to a packaged high power laser diode assembly including a plurality of laser diodes, each laser diode being formed with a meniscus lens within a slow axis collimator to produce a high power output from the laser diode assembly, the laser diode assembly being configured for inclusion in a modular package, reducing the overall physical size or increasing the laser output brightness. Background Art

[0006] Multimode laser diodes are also called wide-area lasers (BALs). Wide-area laser diodes are edge-emitting laser diodes in which the emission region has a strongly asymmetric shape in the form of a wide stripe. Prior art high-power laser diode packages use a fast-axis collimator and a slow-axis collimator to collimate the wide-area laser. These laser diode packages use fast-axis collimator lenses with a focal length of approximately 0.15 mm-5 mm, while high-performance packages have shorter fast-axis collimator lens focal lengths, such as, for example, 0.32 mm focal length. In addition, most laser diode packages use a plano-convex slow-axis collimator lens with a focal length between 5 mm and 15 mm, depending on the slow-axis brightness of the laser diode. Conservation of optical etendue drives the residual divergence of the collimated beam, and minimizing the overall package size of the laser diode package is a long-standing goal.

[0007] Typically, as the width of a wide area laser increases, for example from a 95pm emitter to a 250pm emitter, the reduced brightness of the wider emitter indicates more asymmetry in the optical system. Minimizing asymmetry can be achieved by increasing the focal length of the slow axis collimator, but doing so will negatively impact the overall physical size of the laser diode package. However, the current trend is to reduce the size / volume / mass of laser diode packages, not to increase it. A simplified example is one in which the slow axis focal length in a currently available package accounts for approximately 20mm (i.e., approximately 28%) of the available total package width of approximately 70mm. Devising a method to reduce the focal length of the slow axis collimator, and thereby reduce its back focal length, would result in a reduction in package size / volume / mass. Summary of the invention

[0008] The disclosed high power laser diode packages enable the use of a greater number of emitters in a given package volume. In addition, the disclosed laser diode packages enable the use of larger, wider laser diode emitters in producing higher power laser output. Each of these system design options is enabled by a slow axis collimator lens design in which the light incident surface facing the laser diode has a strong negative lens surface power to cause the beam to diverge outwardly, and the light exit surface has an even stronger positive lens surface power to collimate the rapidly diverging beam.

[0009] As a first example, creating a 5 mm focal length slow axis collimator lens can reduce the physical path from the exit surface of the slow axis collimator lens to the emitting face of the laser diode by 7 mm compared to a standard 12 mm focal length slow axis collimator lens, thereby reducing the size of the laser diode package.

[0010] As a second example, creating a 15mm focal length slow axis collimator lens, but with the same back focal length as a standard 12mm focal length slow axis collimator lens, can help increase the chip-on-submount width from 200pm to 250pm without negatively impacting the component-level numerical aperture or increasing the size of the laser diode package due to the reduced residual divergence of the 15mm focal length slow axis collimator lens.

[0011] Other aspects and advantages will become apparent from the following detailed description of the preferred embodiments, which proceeds with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1A shows the optical component layout of a conventional high power laser diode package.

[0013] 1B and 1C illustrate stacks of individual input laser beams and a compressed laser beam produced by the laser diode package of FIG. 1A .

[0014] FIG. 2A shows a high power laser diode assembly where polarization multiplexing is used to form two beam stacks and which are compressed by a beam compressor.

[0015] 2B and 2C show the beam stack of FIG. 2A before and after compression, respectively.

[0016] FIG. 2D shows a representative stepped laser diode mount for a laser diode bank used in the formation of the two beam stacks of FIG. 2A .

[0017] Figure 3A Figure 3B and Figure 3C is a top view showing the beneficial effect on the overall size of a laser diode package by using a meniscus shaped slow axis collimator lens according to the present disclosure in successive incremental steps.

[0018] Figure 4 is a sequential ray trace diagram that helps illustrate the beneficial effects of using a meniscus slow axis collimator lens with a single wide area laser diode optically associated with a single chip on submount (COS).

[0019] Figure 5 is a plan view layout of an optical assembly in which an implementation replacing a meniscus slow axis collimator lens maintains the nominal focal length of a standard plano-convex slow axis collimator lens but shortens the back focal length.

[0020] Figure 6 is a plan view layout of an optical assembly in which embodiments replace a meniscus slow axis collimator lens to maintain the physical path length but provide a longer focal length than the nominal focal length of a standard plano-convex slow axis collimator lens. DETAILED DESCRIPTION

[0021] 1A , 1B and 1C illustrate the optical component layout of a conventional high power laser diode package using fast axis collimation optics and slow axis collimation optics to collimate wide area laser emitted radiation, and the stack of laser beams produced thereby.

[0022] As an example, FIG1A shows a packaged laser diode assembly 10 included in a laser diode package housing 12. The laser diode assembly 10 includes three wide-area laser diodes 14A, 14B, and 14C that emit laser beams that are collimated by fast-axis collimation optics 16 and slow-axis collimation optics 18. The collimated beams are directed to an objective lens 20 that transmits them to an optical fiber 22.

[0023] For ease of illustration, housing 12 is partially removed. Stepped surface 30 includes a plurality of stepped surface portions 32A, 32B, and 32C to which one or more laser diodes 14A, 14B, and 14C are respectively affixed so as to be generally positioned at different monotonically descending or ascending heights. A single laser diode is generally mounted on each step, and the laser diodes are affixed to the steps so that the laser radiation propagates along substantially parallel axes. Deviations from a parallel arrangement may be compensated as desired, as described below.

[0024] The fast axes of the laser diodes 14A, 14B, and 14C are perpendicular to the plane of the drawing, while the slow axes are in the plane of the drawing. The emitted beams from the laser diodes 14A, 14B, and 14C are received and collimated by the fast axis collimating optics 16 and the slow axis collimating optics 18 to produce collimated beams. An optional volume Bragg grating element 34 may be positioned between the fast axis collimating optics 16 and the slow axis collimating optics 18 to provide locking of the wavelengths of the laser diodes 14A, 14B, and 14C.

[0025] The light reflecting element or turning mirror 36 receives the collimated light beams, which, after collimation, generally propagate parallel to each other. In the example of FIG. 1A , the turning mirror 36 is positioned to reflect the collimated light beams at right angles so that the reflected light beams are directed to the beam compressor 38 . The preferred beam compressor is described in publication number US 2017 / 0235057 (disclosure of U.S. patent application number 15 / 435,117) assigned to the assignee of the present patent application. The propagation direction of the light beam emitted from each of the laser diodes 14A, 14B, and 14C can be adjusted by adjusting one of the corresponding reflectors 36 . At the beam compressor 38 , the fast axes of the reflected light beams are stacked one above the other to form stacked light beams 40A, 40B, and 40C (as shown in FIG. 1B ), which correspond to the laser diodes 14A, 14B, and 14C, respectively, and have a spacing based on the height of the stepped surface portions 32A, 32B, and 32C. The turning mirror 36 and the slow-axis collimating optics 18 may be conveniently secured to a common surface 42 .

[0026] The topmost portion of each turning mirror 36 for each collimated beam is set to a height so that the reflected beam is not clamped by the downstream turning mirror 36. For example, in FIG. 1A, the bottommost mirror in the figure has a maximum height corresponding to the maximum step height of the corresponding stepped surface portion 32A. The beam compressor 38 adjusts the spacing between adjacent stacked beams 40A, 40B, and 40C and then directs the compressed beams toward the objective lens 20, which directs the compressed beams into the optical fiber 22. In some examples, the objective lens 20 is a single plano-convex lens, and in other examples, more complex multi-element lenses are used, including spherical and aspherical surfaces.

[0027] As shown in Figures IB and 1C, the input beam stack of beams 40A, 40B and 40C propagates from beam compressor 38 as a compressed beam stack of beams 44A, 44B and 44C. Comparison of Figures IB and 1C shows that the beam separation and beam diameter are compressed in the compression direction.

[0028] 2A, 2B, 2C and 2D illustrate a laser diode assembly 50, which is described with reference to a right-handed xyz coordinate system 52, with the z-axis extending upwardly out of the plane of FIG. 2A. The laser diode assembly 50 includes laser diode groups 54, 56, 58 and 60 arranged to emit respective laser beam groups to corresponding reflectors and groups 64, 66, 68 and 70 of fast and slow axis collimators. For example, the laser diodes of group 54 emit beams in the x-axis direction, which are then redirected by the respective reflectors of group 64 to propagate in the y-axis direction. The laser diodes of each group are displaced or offset from each other along the z-axis, and the associated reflectors are positioned so that the laser beam from the group is not blocked by the reflectors. As shown in FIG. 2D, the laser diode group 54 is fixed to a stepped mount 72 to provide a suitable z-axis offset. Similar mounts are provided for the remaining laser diode groups. For convenience, the beam propagation axes 74, 76, 78 and 80 of the bottom-most laser diode of each group are shown. The beam propagation axes of the remaining laser diodes in each group are similar to each other but offset along the z-axis.

[0029] The laser beam from laser diode group 54 is directed to half-wave retarder 82 by the reflector of group 64 and then combined with the laser beam from laser diode group 56 (redirected by the reflector of group 66) at polarization beam splitter 84, so that vertically stacked beam group 86A (as shown in FIG. 2B ) is incident on beam compressor 88. The laser beam from laser diode group 60 is directed to half-wave retarder 92 by the reflector of group 70 and then combined with the laser beam from laser diode group 58 (redirected by the reflector of group 68) at polarization beam splitter 94, so that vertically stacked beam group 86B (as shown in FIG. 2B ) is incident on beam compressor 88.

[0030] Mounting surfaces 100 and 102 are provided for laser diodes 54 and 56, and laser diodes 56 and 60, respectively. Uncompressed laser beams from laser diodes 58 and 60 are directed to beam compressor 88 by prism 104. Objective lens 106 directs the compressed beams to input surface 108 of optical fiber 110. Polarizing beam splitters 84 and 94 may be included in respective optical assemblies 112 and 114, which may include prisms to redirect the combined beams.

[0031] FIG2B shows stacked beams 86A and 86B incident on beam compressor 88. FIG2C shows vertically stacked groups 96A and 96B of beams exiting beam compressor 88, where the beam spacing and individual beam heights are modified by the compression ratio M=H2 / H1. In this example, the cylindrical beam compressor applies compression in the z direction rather than the x direction. Additional beam compressors may be provided to compress in other directions, or a beam compressor employing a spherical surface may be used.

[0032] Figure 3A Figure 3B and Figure 3C (collectively, FIG. 3 ) is a top plan view illustrating, in successive incremental steps, the beneficial effect on the overall size of the laser diode package achieved by positioning a meniscus-shaped slow-axis collimator lens between the wide-area laser diode and the turning mirror. FIG. 3 illustrates a set of twelve substantially identical wide-area laser diodes 214A, ..., 214L mounted on respective stepped surface portions (not shown) such that respective laser beams 215A, ..., 215L propagate along substantially parallel axes. The laser beams 215A, ..., 215L are collimated by fast-axis collimating optics 216A, ..., 216L and slow-axis collimating optics 218AS, ..., 218LS, respectively, prior to being incident on the turning mirrors 236A, ..., 236L. Since the twelve laser diodes 214A, ..., 214L are substantially identical, the following description is directed only to laser diode 214A, but is applicable to laser diodes 214B, ..., 214L.

[0033] FIG3A shows a conventional laser diode package 249S that occupies a nominal volume in a laser diode assembly 250S. A divergent laser beam 215A propagating from a laser diode 214A is collimated by a standard plano-convex slow axis collimator lens 218AS, which has a nominal back focal length 252S of 12 mm. The nominal back focal length 252S includes the space occupied by the fast axis collimating optics 216A. The slow axis collimator lenses 218AS, ..., 218LS each have the same nominal back focal length 252S.

[0034] Figure 3BA laser diode package 249I is shown that employs different slow-axis collimating optics than those shown in FIG. 3A , but occupies a nominal volume in the laser diode assembly 250I. A meniscus-shaped slow-axis collimator lens 218AM receives and collimates the diverging laser beam 215A, the meniscus-shaped lens having a first or light incident surface 254A and a second or light exit surface 256A. The light incident surface 254A imparts a negative lens surface power to cause the laser beam 215A to diverge outward at a rate greater than the relatively slow initial divergence rate of the laser beam 215A, thereby forming a rapidly diverging laser beam 215AD. The light exit surface 256A imparts a positive surface power to the rapidly diverging laser beam 215AD that is stronger than the negative lens surface power to collimate the rapidly diverging laser beam 215AD and thereby form a collimated laser beam 215AC. The meniscus-shaped slow-axis collimator lens 218AM has a 5 mm back focal length 252M. Figure 3B The placement of the meniscus-shaped slow-axis collimator lens 218AM is shown to create a dead zone 258A through which the collimated laser beam 215AC propagates between the light exit surface 256A and the turning mirror 236A.

[0035] Figure 3C The laser diode package 249M in the laser diode assembly 250M is shown, and its back focal length 252M is 5 mm. Figure 3B The meniscus-shaped slow axis collimator lens 218A is more compact without a dead zone 258A between the light exit surface 256A and the turning mirror 236A. The overall size of the laser diode package is reduced by 7 mm. Therefore, the volume occupied by the laser diode package 249M is smaller than the nominal volume occupied by the laser diode package 249S.

[0036] Figure 4 3A . A sequential ray trace diagram is presented which helps to illustrate the beneficial effect of positioning a meniscus slow axis collimator lens with a single wide area laser diode 314 optically associated with a single chip on a submount (COS). This embodiment creates a longer focal length slow axis collimator lens having the same nominal back focal length as the standard plano-convex slow axis collimator lens 218AS of FIG. 3A . When each of the multiple wide area diodes is mounted above and the submount width is defined in the laser diode package, the resulting benefit is a smaller residual divergence than the characteristic residual divergence of the collimator lens 218AS, thereby increasing the numerical aperture (i.e., brightness) at the component level without increasing the submount width relative to the nominal focal length.

[0037] Figure 4 The ray trace diagram shows that the laser diode 314 emits three groups of light rays 3141, 3142 and 3143, Figure 4315F in the optical field 315F. Three groups of light rays 3141, 3142 and 3143 represent light rays emitted from one edge, the middle and another edge of the laser diode 314, respectively, as shown in the ray trace diagram generated by the Zemax optical design program. Light rays 3141, 3142 and 3143 propagate through the fast axis collimator lens 316 and are incident on the meniscus slow axis collimator lens 318, which has a first or light incident surface 354 and a second or light exit surface 356. The light incident surface 354 imparts a negative lens surface power to diverge the light rays of the optical field 315F outwardly at a rate greater than a relatively slow initial divergence rate to form rapidly diverging light rays of the optical field 315FD propagating in the meniscus slow axis collimator lens 318. The light exit surface 356 imparts a positive lens surface power to the light of the rapidly diverging light field 315FD that is stronger than the negative lens surface power to collimate the light of the rapidly diverging light field 315FD to form the light of the collimated light field 315FC. The curvatures of the light incident surface 354 and the light exit surface 356 are set to create a meniscus-shaped slow axis collimator lens 318, such as a focal length 360 of 15 mm, but a back focal length 362 of 12 mm, which is the same as the back focal length 252S shown in Figure 3A. Because of their small radius of curvature, the light incident surface 354 and the light exit surface 356 exhibit an aspherical lens surface profile. Therefore, the width of the laser diode 314 can be increased from 200 pm to 250 pm without negatively affecting the numerical aperture at the component level or increasing the size of the laser diode package.

[0038] Another beneficial effect can be achieved for multiple wide-area laser diodes contained within a package, where the emitted laser beams propagate along different path lengths to be incident on a meniscus slow axis collimator lens, thereby exhibiting a slow axis residual divergence. The meniscus slow axis collimator lens is designed such that the meniscus lens focal length is longer than the nominal focal length, and the meniscus lens back focal length is substantially the same as the nominal back focal length, thereby providing a slow axis residual divergence that is less than the characteristic slow axis residual divergence of a standard plano-convex slow axis collimator lens 218AS, thereby reducing the numerical aperture and increasing the brightness.

[0039] The meniscus slow axis collimator lenses of the above embodiments are each a transmissive optical substrate, preferably made of a type of glass operatively compatible with the beam wavelength and power, and having a central glass thickness of a value that minimizes residual divergence of a collimated rapidly diverging beam.

[0040] The following examples present the optical design criteria of laser diode package embodiments, where a meniscus collimator lens replaces the standard 12 mm plano-convex focal length slow-axis collimator. Example 1 is an implementation where the replacement meniscus slow-axis collimator lens maintains the 12 mm nominal focal length of the standard plano-convex slow-axis collimator lens but shortens the back focal length. Example 2 is an implementation where the replacement meniscus slow-axis collimator lens maintains the physical path length but provides a longer focal length than the 12 mm nominal focal length of the standard plano-convex slow-axis collimator lens.

[0041] Example 1 presents the design criteria of a meniscus slow-axis collimator lens for a laser diode package implemented with a laser diode having a 125 pm slow-axis near field and a 9 mm focal length. Figure 5 is a plan view layout of an optical component that includes a laser diode 214A, a fast-axis collimation optical device 216A, and a meniscus slow-axis collimator lens 218AM of a laser diode package 250M, which corresponds to Figure 3C . Figure 5 Shows a laser diode 214A having an emission surface 200 and a center line 222. The field top ray 214A1 is emitted at a distance of 222 + 62.5 pm from the center line 222, the mid-field ray 214A2 is emitted on the center line 222, and the field bottom ray 214A3 is emitted at a distance of 222 - 62.5 pm from the center line 222 of the emission surface 220. The meniscus slow-axis collimator lens 218AM is formed with a uniform aspheric surface, where R1 of the light incident surface 254A is 1.49 mm and R2 of the light exit surface 256A is 2.0 mm. For the uniform aspheric coefficient, there are multiple solutions; thus, for the implementation of Example 1, the value of the conic coefficient K of the surfaces 256A and 254A is -1 < K < 0 (i.e., prolate ellipse). The meniscus slow-axis collimator lens 218AM is made of 1.79 high refractive index glass, specified for 976 nm, and has a center thickness of 2.1 mm.

[0042] The laser diode package embodiment implemented by the above laser diode 214A and meniscus slow-axis collimator lens 218AM has a 5.1 mm back focal length 252M (including the glass of the fast-axis collimation optical device 216A). This results in a total physical path length 260 from the light exit surface 256A of the meniscus slow-axis collimator lens 218AM to the emission surface 220 of the laser diode 214A of 7.2 mm (5.1 mm + 2.1 mm), and the focal length is 25% shorter than the 12 mm nominal focal length ((12 mm - 9 mm) / 12 mm) without degrading the beam quality.

[0043] Conservation of brightness (etendue) means that the residual divergence of the multimode laser diode increases by 25%. However, a "smaller" (125pm) slow-axis near field produces a brighter laser diode than the 250pm laser diode in Example 2 below, so the total residual divergence is nominally conserved with the divergence of a 12mm focal length standard plano-convex slow-axis collimator. The overall result is that smaller, more compact laser diode packages can be used in high brightness applications where total mass and volume are a concern.

[0044] Example 2 presents the meniscus slow-axis collimator lens design criteria for a laser diode package implemented with a laser diode having a slow-axis near field of 250 pm and a focal length of 15 mm. Figure 6 is a plan view layout of the optical components, which includes a laser diode 314, a fast axis collimating optics 316, and a meniscus slow axis collimator lens 318, which corresponds to Figure 4 . Figure 6 A laser diode 314 is shown having an emission surface 320 and a center line 322. A top-of-field ray 3411 is emitted at a distance of +125 pm from the center line 322, a mid-field ray 3142 is emitted at the center line 322, and a bottom-of-field ray 3143 is emitted at a distance of -125 pm from the center line 322 of the emission surface 320. A meniscus-shaped slow-axis collimator lens 318 is formed with a uniform aspheric surface, wherein R1 = 2.59 mm for the light incident surface 354 and R2 = 2.9 mm for the light exit surface 356. There are multiple solutions for uniform aspheric coefficients; therefore, for the implementation of Example 2, the value of the conic coefficient K of surfaces 356 and 354 is K>0 (i.e., an oblate ellipse). The meniscus-shaped slow-axis collimator lens 318 is made of 1.79 high-refractive-index glass, specified as 976 nm, and has a center thickness of 2.14 mm.

[0045] The laser diode package embodiment implemented with the above-described laser diode 314 and meniscus slow axis collimator lens 318 has a 10.4 mm back focal length 362 (including the glass of the fast axis collimating optics 316). This results in a total physical path length 360 of 12.5 mm (10.4 mm + 2.14 mm) from the light exit surface 356 of the meniscus slow axis collimator lens 318 to the emitting face 320 of the laser diode 314, a focal length that is 25% longer (15 mm / 12 mm) relative to the 12 mm nominal focal length without increasing the physical path length.

[0046] The conservation of brightness (etendue) means that the residual divergence of a multimode laser diode is reduced by 25%. The result is the ability to design additional emitters into the laser diode package, since the additional emitters will have a longer path length.

[0047] It will be apparent to those skilled in the art that many changes may be made to the details of the above-described embodiments without departing from the basic principles of the invention. For example, the disclosed laser diode assembly may be constructed using a recently introduced class of wide-area diodes described in U.S. Patent No. 9,166,369 assigned to the assignee of the present patent application, referred to as reduced-mode (REM) diodes. REM diodes are wide-area semiconductor diode laser devices having a flared current injection region extending between a multi-mode high-reflector facet and a partial reflector facet. REM diodes suppress higher-order modes, allowing the use of larger emitters to scale the focal length without affecting the brightness of the slow axis. Accordingly, the scope of the present invention should be determined solely by the appended claims.

Claims

1. A laser diode assembly comprising a plurality of wide-area laser diodes configured to emit a plurality of laser beams to propagate along separate beam axes that are separate from and parallel to each other, each laser diode exhibiting a fast divergence rate in a fast axis direction and a slow divergence rate in a slow axis direction, each of the plurality of emitted laser beams being received and collimated by a fast-axis collimating optic and a slow-axis collimating optic, respectively, to form one of a plurality of collimated laser beams, the collimated laser beams being reflected by a corresponding light reflecting element for delivery to an objective lens, the slow-axis collimating optic having a nominal focal length and a nominal back focal length, and the objective lens directing the plurality of laser beams reflected by the light reflecting element to an optical fiber, wherein The laser diode assembly includes: a transmissive optical substrate having a first surface and a second surface separated along an optical axis and configured to form a meniscus slow axis collimator lens, the meniscus slow axis collimator lens serving as a slow axis collimating optical device, the first surface being positioned to receive one of the plurality of emitted laser beams and having a first curvature, the first curvature imparting a negative lens surface focal length to cause the received one of the plurality of emitted laser beams to diverge outwardly, the rate at which the received one of the plurality of emitted laser beams diverges outwardly is greater than the slow divergence rate, thereby forming a rapidly diverging light beam, the second surface having a second curvature, the second curvature imparting a positive lens surface focal length that is stronger than the negative lens surface focal length to collimate the rapidly diverging light beam; and the meniscus lens focal length of the meniscus slow axis collimator lens is longer than the nominal focal length, and the meniscus lens back focal length of the meniscus slow axis collimator lens is the same as the nominal back focal length.

2. The laser diode assembly according to claim 1, wherein: The slow axis collimating optics exhibit a characteristic slow axis residual divergence, wherein the plurality of wide area laser diodes are housed within a package that causes the laser beams to propagate along different path lengths for incident upon the meniscus shaped slow axis collimator lens, and wherein the meniscus shaped slow axis collimator lens provides a slow axis residual divergence that is less than the characteristic slow axis residual divergence, thereby reducing numerical aperture and increasing brightness.

3. The laser diode assembly according to claim 1, wherein: Each of the plurality of wide-area laser diodes is mounted on a submount in a laser diode package and defines a submount width, and the slow-axis collimating optics exhibit a characteristic slow-axis residual divergence, and wherein the meniscus-shaped slow-axis collimator lens reduces the residual divergence and thereby increases the brightness of laser light emitted from the laser diode package without increasing the submount width relative to the nominal focal length.

4. The laser diode assembly according to claim 1, wherein: The meniscus slow axis collimator lens is a single optical system.

5. The laser diode assembly according to claim 1, wherein: The first curvature has an aspherical surface profile, and the second curvature has an aspherical surface profile.

6. The laser diode assembly of claim 1, wherein: The first curvature and the second curvature are respectively associated with a first radius of curvature and a second radius of curvature, the second radius of curvature being longer than the first radius of curvature.

7. The laser diode assembly of claim 1, wherein: One of the received multiple transmitted laser beams has a laser beam wavelength and focal length, and wherein the transmissive optical substrate is a glass operably compatible with the beam wavelength and focal length, and the central glass thickness of the transmissive optical substrate has a value that minimizes residual divergence of the collimated rapidly diverging light beam.

8. The laser diode assembly of claim 1, wherein: The plurality of wide-area laser diodes include reduced mode diodes.

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