Semiconductor laser and manufacturing process for a semiconductor laser

Abstract

Semiconductor laser (1) with a housing (2) and with several laser diode chips (31, 32, 33) encapsulated in the housing (2), wherein: - the housing (2) comprises a top plate (23) and / or a side wall (20) that is transparent to laser radiation (41, 42, 43) generated during operation; - the top plate (23) and / or the side wall (20) has a light-emitting surface (24) with adjacent emission regions (61, 62, 63); - each of the emission regions (61, 62, 63) is assigned to exactly one of the laser diode chips (31, 32, 33); - a light emission plane (26) is arranged downstream of the light emission surface (24) in a beam path; and - the top plate (23) and / or the side wall (20) are in the emission regions (61, 62, 63) has different mean thicknesses, so that an optical path length for the laser radiation (41, 42, 43) of all laser diode chips (31, 32, 33) to the light exit plane (26) is the same with a tolerance of at most 3 µm.

Description

[0001] A semiconductor laser is specified. Furthermore, a manufacturing process for a semiconductor laser is described.

[0002] One challenge to be solved is to specify a semiconductor laser that can be manufactured efficiently and emits radiation with defined optical properties.

[0003] This problem is solved, among other things, by a semiconductor laser and by a manufacturing process with the features of the independent patent claims. Preferred embodiments are the subject of the dependent claims.

[0004] According to at least one embodiment, the semiconductor laser comprises a housing. The housing is preferably hermetically sealed. For example, the housing comprises a semiconductor material such as silicon and / or germanium or a metallic substrate, such as a molybdenum plate. Furthermore, the housing preferably comprises at least one transparent material, such as glass and / or sapphire. The housing may also contain plastics. Hermetically sealed means that no significant exchange of substances such as oxygen or water vapor takes place between the interior and exterior of the housing. Hermetically sealed means, for example, that the leakage rate is at most 5 × 10⁻⁶. -9 Pa m / s, especially at room temperature.

[0005] According to at least one embodiment, the housing comprises one or more laser diode chips. The at least one laser diode chip is housed and encapsulated within the housing. In particular, the laser diode chips are located in a recess in the housing.

[0006] According to at least one embodiment, the housing includes a cover plate. The cover plate is at least partially transparent to the laser radiation generated during operation. The cover plate can be made of a single, homogeneous material. Alternatively, the cover plate includes areas transparent to the laser radiation that are embedded in another material, whereby the other material need not be transparent to the laser radiation. The cover plate is a window through which the laser radiation exits. The cover plate includes a light-emitting surface for the laser radiation generated during operation.

[0007] Preferably, the cover plate forms a lid for the housing, and can close a recess in the housing. The laser diode chips are preferably mounted on the bottom of the recess, so that the cover plate can be spaced apart from the laser diode chips. Thus, the cover plate is preferably distinct from a mounting platform for the laser diode chips.

[0008] According to at least one embodiment, the light-emitting surface comprises adjacent emission zones for the laser radiation. In a top view of the light-emitting surface, the emission zones preferably do not overlap. The distance between adjacent emission zones is, for example, at least 0.1 mm, 0.4 mm, or 1 mm.

[0009] As an alternative to the top plate, a side wall of the housing can serve as the exit window for the generated laser radiation. The light-emitting surface with its adjacent exit areas is then located in the side wall, specifically on one of its outer sides. Furthermore, the light-emitting surface with its adjacent exit areas can be distributed across one or more side walls and the top plate. The preceding and subsequent statements regarding the top plate apply equally to a side wall if the side wall encompasses at least one of the exit areas.

[0010] Alternatively, the function of the top plate can also be performed by a base plate on which the laser diode chips are mounted. In this case, the characteristics of the top plate apply accordingly to the base plate.

[0011] According to at least one embodiment, each of the output areas is assigned to exactly one of the laser diode chips. A 1:1 assignment preferably exists between the output areas and the laser diode chips.

[0012] According to at least one embodiment, a light emission plane is arranged downstream of the light emission surface in a beam path. The light emission plane is preferably oriented perpendicular to the emission directions of the laser diode chips after passing through the light emission surface. It is possible that the light emission surface lies within the light emission plane, at least in areas outside the emission regions.

[0013] According to at least one embodiment, the cover plate has different average thicknesses in the exit regions. That is, the cover plate is thinner in at least one exit region than in at least one other. Due to the different thicknesses of the cover plate in the exit regions, the optical path length for the laser radiation from all laser diode chips to the light exit plane is the same. "Same" means, in particular, that the differences in the optical path lengths are at most 3 µm, 1.5 µm, or 1 µm. Preferably, the angular tolerance of the respective laser radiation, for example, with respect to the light exit plane, is also at most 2°, 1°, or 0.5°.

[0014] In at least one embodiment, the semiconductor laser comprises a housing in which one or more laser diode chips are encapsulated. The housing includes a top plate and / or a side wall that is transparent to the laser radiation generated during operation. The top plate and / or the side wall has a light-emitting surface with adjacent emission regions. Exactly one of the laser diode chips is assigned to each emission region. A light emission plane is located downstream of the light emission surface in a beam path. The top plate and / or the side wall has different average thicknesses in the emission regions, such that the optical path length for the laser radiation from all laser diode chips to the light emission plane is the same with a tolerance of at most 3 µm or at most 1.5 µm.

[0015] When combining multiple laser beam sources, such as laser diodes, to focus their radiation at a single point, it can be advantageous to use a common optical element for focusing. The focal plane of this optical element is determined by the optical path length between the respective laser beam source and the optical element. This requires precisely setting the optical path length for all laser beam sources to ensure that the focal point is at the same distance from the optical element for each source. Additionally, it may be necessary to precisely adjust the direction of the beam axes of the sources.

[0016] This traditionally requires highly precise positioning of the laser beam sources. If the laser diodes are mounted on pedestals, so-called submounts, the submounts themselves must also be mounted with high precision within the housing. If additional optical elements are integrated into the housing, these elements must also be mounted with high precision. Furthermore, it can be advantageous to precisely align not only the optical path but also the direction of the beam axes to simplify the assembly of downstream optics. This applies equally to semiconductor lasers with a single laser diode chip and those with multiple laser diode chips.

[0017] High-precision passive placement of the required components without operating the laser beam sources is typically problematic because accurately identifying laser facets is difficult. Using a laser diode's metallization as an orientation point is usually not feasible, as such metallizations are not aligned with the facets with sufficient precision. Furthermore, placing laser diodes or optical components with high precision is comparatively slow and therefore expensive. Similarly, conventional active placement, where the laser diodes are operated, is also comparatively slow and therefore expensive.

[0018] Furthermore, a laser diode cannot be operated at soldering temperatures; that is, adjustment must be performed near room temperature. Subsequently, the laser diode and the submount must be brought up to soldering temperature and soldered. This requires long cycle times, meaning the laser diodes must be held at soldering temperature for an extended period, especially if multiple laser diodes are soldered onto a common submount. This often negatively impacts the lifespan of the laser diodes.

[0019] In the semiconductor laser described here, the optical path length is adjusted according to the manufacturing process described here by individually changing the path length of the irradiated window for each beam from the laser diode chips after all laser diode chips have been placed and fixed. For this to be achieved, the light cones of the individual laser diode chips must not overlap within a window, and especially not at the light-emitting surface.

[0020] Thus, by locally changing the thickness of the window or the refractive index in the area through which the light passes, the optical path for each laser diode chip can be individually adjusted. Furthermore, by locally changing the orientation of the light-emitting surface in the exit areas, the beam direction can be individually influenced and adjusted through light refraction.

[0021] Path length adjustment and / or surface adaptation can be achieved, for example, through local laser ablation of the window in the exit areas. The window, i.e., the cover plate, can have a high refractive index to achieve a significant effect on the optical path length with shallow ablation depths. Alternatively, the properties of a window, such as one made of glass, can be locally modified by laser irradiation, thereby increasing the etchability of the window material in that area. In a further step, the window is etched, with material preferably being removed from the exit areas.

[0022] This allows for a local reduction in the window's thickness and controllable surface alignment. Furthermore, it is possible to locally alter the refractive index of a window, for example one made of glass, by laser irradiation, thus changing the optical path while maintaining the same thickness.

[0023] Furthermore, it is possible to apply a material to the cover plate in a localized manner, for example by laser sintering. The applied material preferably has a high refractive index in order to achieve a large difference in optical path length with thin layers.

[0024] These methods allow the path length difference between the laser diode chips and the light output plane to be adjusted and equalized. For this purpose, the optical path length of all laser diode chips is measured beforehand. Preferably, no modification is made to the cover plate for the laser diode chip with the smallest or largest path length. For the other sources, the cover plate is modified to adjust the optical path length to the desired value.

[0025] It is possible to minimize the path length difference. Alternatively, the path length difference can be set to a target value, for example, to pre-compensate for chromatic aberration in a downstream optical system. Furthermore, it is possible to modify the material of the cover plate in all exit areas to set the optical path length for all laser diode chips to a predefined target value.

[0026] Since the housing can be fully assembled and sealed before the cover plate is machined, the laser diode chips can be operated to directly measure the focus position and / or beam direction of each chip, thus determining the necessary material removal or deposition in the exit areas. Furthermore, the focus positions and / or beam directions can also be measured simultaneously during the cover plate machining process to directly control the machining process.

[0027] The semiconductor laser described here significantly reduces the required assembly accuracy of the laser diode chips and optical elements, thus reducing equipment complexity and increasing processing speed. This is cost-effective and reduces the thermal stress on the laser diode chips during soldering.

[0028] In contrast, conventional methods require the precise assembly of multiple components, as the target parameters, particularly the focus position, depend on cumulative assembly errors. However, the manufacturing process described here compensates for the cumulative assembly errors of all components together after assembly. With conventional passive component placement, only the physical path can be controlled, and this path only indirectly determines the focus position. In contrast, the method described here allows the focus position and / or beam direction—the target parameters—to be directly measured and adjusted.

[0029] Conventional methods require complex and precise processing of each semiconductor laser, even those that do not meet specifications due to defects or process variations. The manufacturing process described here allows semiconductor lasers to be tested at an early stage and, if necessary, rejected before the complex processing of the cover plate.

[0030] According to at least one embodiment, the exit regions, or at least one of the exit regions, or most of the exit regions, are flat sub-surfaces of the light-emitting surface. That is, the exit region in question exhibits no or no significant curvature for the laser radiation.

[0031] Alternatively, at least one or all of the exit regions can have a defined curvature. Such curvature can be used, for example, to adjust the beam profile of the laser radiation or to achieve a focusing or diverging effect. In other words, the exit regions can be shaped similarly to a lens or corrective optics.

[0032] According to at least one embodiment, the laser diode chips are edge-emitting semiconductor laser chips. In this case, an active zone of the laser diode chips is preferably oriented parallel or approximately parallel to the light emission plane. The emission of the laser radiation from the laser diode chips thus occurs parallel to the active zone, i.e., parallel or approximately parallel to the light emission plane. "Approximately" means, for example, an angular tolerance of at most 5°, 2°, or 1°.

[0033] Alternatively, the laser diode chips can also be surface-emitting laser chips that emit perpendicular or approximately perpendicular to the light-emitting plane. Furthermore, it is possible that edge-emitting semiconductor laser chips are mounted in the housing in such a way that emission occurs perpendicular or approximately perpendicular to the light-emitting plane.

[0034] According to at least one embodiment, one or more deflection optics are arranged in the housing. The at least one deflection optic is configured to deflect the laser radiation generated during operation towards the top plate, in particular in a direction perpendicular or approximately perpendicular to the light output plane. For example, the deflection optic is a 45° mirror. The deflection optic is preferably reflective and planar.

[0035] According to at least one embodiment, the housing comprises a base plate. Optionally, the housing further comprises a middle section, wherein such a middle section is located between the base plate and the top plate.

[0036] According to at least one embodiment, the base plate, the cover plate, and the optional middle section are joined together by anodic bonding and / or soldering. Alternatively or additionally, another joining technique, such as adhesive bonding or wafer bonding, can be used to connect the base plate, the cover plate, and the optional middle section. This allows the laser diode chips to be hermetically encapsulated within the housing.

[0037] According to at least one embodiment, the middle section and the top plate are made of the same material. For example, glass is used. The middle section and the top plate are preferably joined to each other by anodic bonding. The base plate is, for example, made of a semiconductor material such as silicon. Alternatively, the base plate is a printed circuit board, for example, made of a ceramic material or based on a metal, such as a metal-core circuit board.

[0038] According to at least one embodiment, the central part comprises the deflecting optics. Preferably, exactly one deflecting optic is provided, which, as an inclined boundary surface of a recess in the central part, directs all laser beams from the laser diode chips towards the top plate. In this case, the laser diode chips are preferably arranged in the recess of the housing, particularly the central part.

[0039] According to at least one embodiment, the thickness of the cover plate is at least 0.1 mm, 0.2 mm, or 0.3 mm, at least outside the outlet areas. Alternatively or additionally, this thickness of the cover plate is at most 2 mm, 1 mm, 0.5 mm, or 0.3 mm.

[0040] According to at least one embodiment, the thickness reduction of the cover plate in at least one of the outlet areas is at least 30 µm or 50 µm or 0.1 mm or 0.14 mm, or the cover plate is designed for such a thickness reduction or maximum thickness reduction. The actual or potential thickness reduction can be comparatively large relative to the thickness of the cover plate. For example, the thickness reduction in at least one of the outlet areas is at least 20% or 35% or 50% and / or at most 80% or 70% of the thickness of the cover plate outside the outlet areas, or such a thickness reduction is enabled.

[0041] Depending on the statistically varying accuracy of the placement, particularly of the laser diode chips, it is possible that for some semiconductor lasers only a relatively small reduction in thickness in the exit regions is necessary to achieve the desired optical path length with the required accuracy. For example, maximum thickness changes of only 3 µm or 20 µm are required in one or all of the exit regions.

[0042] Previously, only a reduction in thickness was specified. The same values ​​apply analogously to an increase in thickness through material loading, as well as to a change in optical path length by means of a change in refractive index, without a change in geometric thickness.

[0043] According to at least one embodiment, the refractive index of the cover plate for the laser radiation generated during operation is at least 1.4 or 1.6. Alternatively or additionally, the refractive index is at most 2.5 or 2.0 or 1.8 or 1.6. In the case of a glass cover plate, the refractive index is preferably between 1.4 and 1.6 inclusive. These values ​​for the refractive index apply to the wavelength of the respective laser radiation and, in particular, at a temperature of 300 K, i.e., approximately room temperature.

[0044] According to at least one embodiment, the emission areas have different shapes when viewed from above and / or in cross-section through the light emission surface. For example, when viewed from above, the emission areas are rectangular, elliptical, or circular. In cross-section, the emission areas are preferably straight line segments or arc-shaped or hyperbolic curve segments.

[0045] According to at least one embodiment, at least one, all, or most of the emission areas are oriented obliquely to the light emission plane. The angle between the light emission plane and the emission area in question is preferably relatively small and is, in particular, at most 5° or 3°. Alternatively or additionally, this angle is at least 0.2°, 0.5°, 1°, or 1.5°.

[0046] According to at least one embodiment, the cover plate has a light-entry surface. The light-entry surface is opposite the light-emission surface. The light-entry surface is preferably flat. It is possible that the light-entry surface has an optically effective coating such as an anti-reflective coating.

[0047] According to at least one embodiment, the optical distance between the laser diode chips and the light-entry surface along the beam path of the respective laser radiation is at least 0.2 mm, 0.3 mm, or 0.5 mm. Alternatively or additionally, this optical distance is at most 3 mm, 2 mm, or 1.5 mm. In other words, the light-entry surface is optically located relatively close to the laser diode chips. The beam path is initially approximately parallel to the light-entry surface and then, from the optional deflecting optics onward, approximately perpendicular to the light-entry surface.

[0048] According to at least one embodiment, the semiconductor laser is designed as an RGB unit. Thus, at least one of the laser diode chips is configured to generate red light, at least one of the laser diode chips to generate green light, and at least one of the laser diode chips to generate blue light. These laser diode chips are preferably electrically operable independently of one another.

[0049] Furthermore, it is possible that additional laser diode chips are present that emit radiation in non-visible spectral ranges, for example laser diode chips for generating near-ultraviolet radiation and / or for generating near-infrared radiation.

[0050] According to at least one embodiment, a beam shaping optic and / or a movable deflecting mirror are arranged downstream of the laser diode chips. The beam shaping optic and / or the movable deflecting mirror are preferably located outside the housing. Such a beam shaping optic and / or a movable deflecting mirror can be housed in a further housing, which also contains the housing of the semiconductor laser with the laser diode chips.

[0051] According to at least one embodiment, at least one or all of the emission areas of the cover plate are directly provided with one or more antireflective coatings. The at least one antireflective coating can extend continuously over the light emission surface or be limited to the emission areas or to a specific emission area.

[0052] According to at least one embodiment, the exit areas, viewed from above on the light exit plane, are arranged along a straight line. In particular, optical centers, i.e., points where optical axes intersect the exit areas, lie on a straight line.

[0053] According to at least one embodiment, the average roughness of the exit areas is at most 0.3 µm, 0.2 µm, 0.1 µm, 0.05 µm, or 0.02 µm. The exit areas are therefore comparatively smooth.

[0054] Furthermore, a manufacturing process for such a semiconductor laser is specified. Features of the manufacturing process are also disclosed for the semiconductor laser, and vice versa.

[0055] In at least one embodiment, the method comprises the following steps, preferably in the specified order: A) Providing the housing, preferably with the laser diode chips already encapsulated inside, B) Operating the laser diode chips and measuring the emission characteristics of each of the laser diode chips, C) Modifying the top plate and / or the side wall in the exit areas so that positioning tolerances of the laser diode chips in the housing are compensated and the optical path length for the laser radiation of all laser diode chips to the light exit plane is equal to a tolerance of at most 3 µm or at most 1.5 µm and / or is equal to a previously specified target value with a tolerance of at most 3 µm or at most 1.5 µm.

[0056] Alternatively, instead of encapsulating the laser diode chips before operation and measurement, it is possible to operate and measure them under evacuation or in a protective atmosphere. The cover plate can then be machined separately, independently of the other components of the semiconductor laser. Only after machining is the cover plate applied to at least one other component of the housing, so that the laser diode chips are encapsulated only after the exit areas have been created. This is particularly advantageous if machining the cover plate could damage other components of the semiconductor laser, such as optics or the laser diode chips themselves.

[0057] According to at least one embodiment, in step C) material is removed from the cover plate. Thus, the cover plate is thinner in at least one of the outlet areas than in the areas adjacent to the outlet areas. Alternatively, material is applied so that the cover plate is thicker in the outlet area in question than in areas adjacent to the outlet areas.

[0058] According to at least one embodiment, material removal is carried out by means of laser ablation and / or by means of laser-induced structural modification in combination with subsequent etching.

[0059] As an alternative to material removal or addition, the geometric thickness of the cover plate can remain constant, while the optical thickness is varied by changing the cover plate material. This means that the refractive index of the cover plate material is locally altered, for example, using laser radiation.

[0060] According to at least one embodiment, after step C), the light-emitting surface is smoothed in at least one of the exit regions. This smoothing is preferably carried out by means of laser polishing. This allows irregularities or roughness of the light-emitting surface in the exit regions to be reduced or eliminated. Such roughness results, for example, from laser ablation.

[0061] The following section provides a more detailed explanation of a semiconductor laser and a manufacturing process described herein, with reference to the drawing and illustrated by exemplary embodiments. Identical reference numerals indicate identical elements in the individual figures. However, the figures are not to scale; rather, individual elements may be exaggerated for clarity.

[0062] They show: Fig. 1 a schematic perspective representation of an embodiment of a semiconductor laser described herein, Fig. 2 to Fig. 4 schematic sectional views of exemplary embodiments of semiconductor lasers described here, Fig. 5 a schematic perspective representation of a cover plate for the semiconductor lasers described here, Fig. 6 to Fig. 8 Calculations relating to path length difference for the semiconductor lasers described here, Fig. 9 a schematic sectional view of an embodiment of a semiconductor laser described herein, Fig. 10 and Fig. 11 Calculations for a tilting of exit regions for semiconductor lasers described here, Fig. 12 and Fig. 13 schematic sectional views of exemplary embodiments of semiconductor lasers described herein, Fig. 14 to Fig. 18 schematic cross-sectional views of steps in a manufacturing process for the semiconductor lasers described here, and Fig. 19 a schematic sectional view of an embodiment of a semiconductor laser described herein.

[0063] In Fig. Figure 1 is an embodiment of a semiconductor laser. 1 shown. The semiconductor laser 1 includes three laser diode chips 31 , 32 , 33 , which are preferably designed to generate red, green, and blue light. The laser diode chips 31 , 32 , 33 are optionally mounted on an intermediate support 30 attached. Such an intermediate support 30 This is also referred to as submount. The laser diode chips 31 , 32 , 33 These are edge-emitting laser chips.

[0064] The laser diode chips 31 , 32 , 33 are located in a housing2 The casing 2 consists of a base plate 21 , a middle section 22 and a cover plate 23 . Via a soldered connection 27 are the base plate 21 and the middle part 22 hermetically sealed together. A connection between the top plate 23 and the middle part 22 is preferably bonded without fasteners via anodic bonding. The central part 22 and the cover plate 23 are preferably made of a glass and for laser radiation generated in operation 41 , 42 , 43 transparent. The laser diode chips 31 , 32 , 33 are therefore located in a recess 28 of the middle section 22 .

[0065] In Fig. Figure 2 is a cross-sectional view of the semiconductor laser. 1 the Fig. 1 shown. The laser diode chips 31 , 32 , 33emit laser radiation 41 , 42 , 43 in a direction parallel to a light emission plane 26 The light emission plane 26 largely runs within a light-emitting surface 24 the cover plate 23 . At a deflecting optic 51 will the laser radiation 41 , 42 , 43 towards the top plate 23 deflected. Via a flat light-entry surface. 25 The laser radiation occurs 41 , 42 , 43 into the top plate 23 a.

[0066] In the light emission surface 24 The cover plate 23 furthermore, several exit areas 61 , 62 , 63 for the respective laser diode chips 31 , 32 , 33 up. The exit areas 61 , 62 , 63 are in Fig. 1 symbolized by ellipses, in Fig. 2 through a hatched area. Top view of the light-emitting surface. 24 The exit areas are located 61 , 62 , 63 side by side. In the exit areas 61 , 62 , 63 A correction is made to an optical path length of the laser radiation. 41 , 42 , 43 .

[0067] This correction to the optical path length is in the Fig. 3 and Fig. 4 illustrated in more detail. Fig. 3 is the top plate 23 in their original state, still without correction and essentially still without the exit areas 61 , 62 , 63 , shown. The Fig. 4 shows that the cover plate 23 in the exit areas 61 , 62 , 63 It has different thicknesses. The different thicknesses and the different refractive index of the cover plate compared to its surroundings are discussed below.23 A correction is made to the desired optical path length between the undrawn laser diode chips and the light exit plane. 26 .

[0068] In areas of the top plate 23 , in which the cover plate 23 The light emission plane lies where the original thickness is still present. 26 in the light-emitting surface 24 The light emission plane 26 This can therefore be at least a partially fictitious plane, which is oriented in particular perpendicular to a main emission direction of the laser diode chips. The exit region 62 , in which the cover plate 23 The area that has not been altered lies in the light emission plane. 26 .

[0069] In Fig. 5 is an example of a finished cover plate. 23 drawn without the remaining components of the semiconductor laser 1 It can be seen that the exit areas 61 , 62can have different basic shapes, viewed from above on the light-emitting surface 24 As seen. The same applies to all other examples.

[0070] The cover plate of the Fig. 5 can be separated from the other components of the housing. 2 to be manufactured. For this purpose, the laser diode chips are used. 31 , 32 , 33 For example, it is operated and measured in a protective gas atmosphere. The correction data obtained from the measurement are used to adjust the cover plate. 23 to edit or at least partially edit.

[0071] The at least partially machined cover plate 23 This is then used to close the housing. 2 used. If necessary, a further adjustment of the exit areas can be made. 61 , 62 , 63 This will happen when the cover plate 23 already applied by the laser diode chips 31 ,32 , 33 be operated and measured again, and the exit areas 61 , 62 , 63 will be edited again.

[0072] Will the cover plate 23 exclusively separately from the other components of the semiconductor laser 1 processed, so the exit areas can be 61 , 62 , 63 They may also be located at the light-entry surface and not necessarily at the light-emission surface. The previously described characteristics of the light-emission surface then apply accordingly to the light-entry surface. The same applies to all other embodiments.

[0073] In the scheme of Fig. 6 and in the associated calculations of Fig. 7 and Fig. Section 8 explains how to correct the thickness in the exit areas. 62 , 63 to be done, exemplified by two laser diode chips 32 , 33 with laser radiation42 , 43 illustrated. The laser diode chips 32 , 33 are located in a gas or in an evacuated area of ​​the recess 28 with a refractive index n of 1 or approximately 1. In this area, the laser radiation 43 a route x a It traveled back in the air.

[0074] The subscript "a" stands for air. The distance x g is in the medium of the cover plate 23 covered, for example a glass with a refractive index n of 1.5. The index g stands for glass.

[0075] Out of Fig. Figure 7 shows that the path length difference Δx g for laser radiation 42 , according to the change in thickness of the cover plate 23 in the relevant exit area 62 , from the difference in path length Δx a in the recess 28Dividing by the refractive index n - 1 yields... For a refractive index of the cover plate 23 A value of approximately 1.5 means that the thickness correction Δx g approximately twice the optical path length difference Δx a in the recess 28 corresponds.

[0076] In Fig. 8 is an estimate for the necessary precision in designing the thickness of the cover plate. 23 in the exit areas 61 , 62 , 63 shown. The permissible tolerance. Δx g for the thickness of the cover plate 23 depends on the allowed tolerance of the optical path length Δp and the refractive index n the cover plate. For example, for an allowed tolerance of the optical path lengths. Δp of 1.5 µm and a refractive index n the cover plate 23 A tolerance of 1.5 results in a tolerance for thickness variations. Δx g of 3 µm.

[0077] Do the laser diode chips indicate 31 , 32 , 33 for example, a mounting tolerance of + / - 10 µm, relative to the deflecting optics 51 This results in a maximum difference in the optical paths of 20 µm. To minimize the maximum tilt angle... α To compensate for a deviation of, for example, 4°, a path length difference of approximately 50 µm is also required. The optical path length to be corrected is therefore approximately 70 µm. This results in a change in the thickness of the cover plate. 23 of a maximum of 140 µm with a refractive index of 1.5 for the cover plate 23 The refractive index of the cover plate is... 23 For example, at 1.8, the necessary thickness change of the cover plate 23 at only approximately 90 µm.

[0078] The distance x a in the recess 28 For example, the thickness is approximately 0.5 mm. x g the cover plate 23, i.e., the original thickness of the top plate 23 , for example, is 200 µm. This results in a total distance up to the light emission plane. 26 an optical path length of approximately 800 µm, which would need to be corrected by up to approximately 70 µm, or approximately 10%.

[0079] In Fig. Figure 9 illustrates that the exit areas 41 , 42 , 43 not only do they have different thicknesses, but they are also angled to the light emission plane. 26 are arranged. Due to the slanted exit areas. 61 , 62 Can a correction of the exit angle of the laser beams be achieved? 41 , 42 , 43 This will happen. Fig. 9. Schematic representation of laser radiation 41 , 42 , 43 shown.

[0080] Calculating a tilt angle γ the exit areas 61 , 62 , 63, in order to achieve the necessary angle correction, is in the Fig. 10 and Fig. Figure 11 illustrates this in more detail. S1 refers to the light-entry surface. 25 and S2 to the relevant exit area 61 , 62 , 63 .

[0081] For a refractive index n2 of the cover plate 2 A value of 1.5 results for an entry angle. α of 3°, which needs to be corrected, an angle γ of the relevant exit area 61 , 62 , 63 of 2.4°. Is the angle to be corrected... α At 1.5°, the correction angle is γ at approximately 1.2°. A target angular tolerance with which the emitted and through the cover plate 23 corrected laser radiation 41 , 42 , 43 perpendicular to the light emission plane 26 The temperature is preferably at a maximum of 1°.

[0082] In Fig. 12 is another embodiment of the semiconductor laser 1 illustrated. The recess 28 is directly in the base plate 21 manufactured. Furthermore, a separate deflection optic is included. 51 present. The light entry area 25 It can be curved and, for example, shaped like a lens. At the light-emitting surface. 24 in the exit areas 61 , 62 , 63 low roughness can 29 of, for example, a maximum size of 100 nm. These in conjunction with Fig. The 12 variants mentioned can also be present individually or in any combination in all other embodiments.

[0083] In the exemplary embodiment of the Fig. 13 are all laser diode chips 31 , 32 , 33 of the semiconductor laser 1 a common beam process optics 52 and a common movable deflecting mirror 53subordinate. These optical elements 52 , 53 This applies to all laser radiation. 41 , 42 , 43 planned. The components 1 , 52 , 53 may be integrated into a common additional housing, not shown.

[0084] For example, the components 1 , 52 , 53 the Fig. 13 a component in a VR headset or in an AR headset, where VR stands for virtual reality and AR for augmented reality.

[0085] In the Fig. 14 to Fig. 17 is an example of a manufacturing process for embodiments of semiconductor lasers 1 illustrated. According to Fig. 14. The encapsulated laser diode chips 31 , 32 , 33 in the case 2 Provided and operated temporarily. Via optional measuring optics. 82as well as via a camera 81 An analysis of the optical path length and / or the direction of radiation and / or the beam profile of the laser radiation is performed. 41 , 42 , 43 This measurement is used to calculate the future exit areas. 61 , 62 , 63 to be designed.

[0086] In Fig. Figure 15 illustrates that a laser beam 71 an ablation of material from the cover plate 23 This has been done.

[0087] The steps of Fig. 14 and Fig. 15 can be performed iteratively, or the step of Fig. 15 simultaneously with the step of the Fig. 14, so that the laser diodes 31 , 32 , 33 during the processing of the cover plate 23 can be operated and the material removal can be actively controlled.

[0088] In the optional step of Fig. Figure 16 shows that the surface created, for example, by laser ablation, has a roughness for the exit areas. 21 features. Via a laser beam 23 , especially infrared laser radiation, laser polishing and thus smoothing can be achieved.

[0089] Thus, see Fig. 17, a smooth exit area 61 , 62 , 63 Optionally, the exit areas can be 61 , 62 , 63 with an anti-reflective coating 54 They can be provided with a common anti-reflective coating or individual anti-reflective coatings can be applied. The anti-reflective coating 54 can cover the entire surface of the light emission area 24 extend or even just locally within the relevant exit area 61 , 62 , 63 appropriate.

[0090] In Fig. 18 is an alternative method for shaping the exit areas 61 , 62 , 63 illustrated. By means of a laser beam. 72 A structural change of material occurs within the cover plate. 23 , where a desired geometry of the exit areas 61 , 62 , 63 is defined. These material changes can be etched out with a subsequent, unmarked etching process, so that the exit areas are defined. 61 , 62 , 63 This results in [unclear - possibly referring to a specific method or technique]. Such a method is also known as stealth dicing.

[0091] Furthermore, as a variant in Fig. 18 shows that the recess 28 in the top plate 23 is present. The base plate 21 This allows for a flat design, eliminating the need for a central section. Furthermore, it is possible that the laser diode chips 31 , 32 , 33surface-emitting laser diode chips are or edge-emitting laser diode chips that emit light approximately in a direction perpendicular to the light-entry surface. 25 emit. These variations can occur individually or in combination in all other embodiments as well.

[0092] In contrast to the procedural steps of the Fig. 15 and Fig. Alternatively, for example, an additional material can be applied to the top plate via laser sintering. 23 a layer is applied so that the thickness increases locally. Alternatively or additionally, it is also possible to change the refractive index locally within the cover plate. 23 This is done so that the geometric thickness of the cover plate 23 does not need to be changed.

[0093] In the preceding figures, the thickness variation for the exit areas was performed. 61 , 62 , 63 each in the top plate 23of the case 2 In contrast, the top plate 23 in Fig. 19 no targeted thickness variation, but a side wall 20 is connected to the exit areas 61 , 62 , 63 provided. This allows the visual thickness of the side wall to vary. 20 In some areas, to correct the optical path length and / or the beam direction. With this arrangement, deflecting optics can be omitted. The side wall 20 is preferably one-piece with the middle part 22 executed.

[0094] The aforementioned characteristics pertain to the exit areas 61 , 62 , 63 in the top plate 23 The same applies to exit areas. 61 , 62 , 63 , which according to Fig. 19 in the side wall 20 condition.

[0095] The invention described here is not limited by the description based on the exemplary embodiments. Rather, the invention encompasses every new feature as well as every combination of features, which in particular includes every combination of features in the patent claims, even if this feature or combination itself is not explicitly specified in the patent claims or exemplary embodiments. Reference symbol list 1 semiconductor laser 2 cases 20 side wall 21 Base plate 22 Middle section 23 Cover plate 24 Light emission area 25 Light entry area 26 Light emission plane 27 Soldered connection 28 Exclusion 29 Roughness 30 intermediate beams 31 laser diode chips for red light 32 laser diode chips for green light 33 laser diode chips for blue light 34 Bond wire 41 red laser radiation 42 green laser radiation 43 blue laser radiation 51 Deflection optics 52 Beam shaping optics 53 movable deflecting mirror 54 Anti-reflective coating 61 Red light exit area 62 Exit area for green light 63 Blue light exit area 71 Laser beam for ablation 72 Laser beam for structural modification 73 Laser beam for laser polishing 81 Camera 82 Measuring optics

Claims

[1] Semiconductor laser (1) with a housing (2) and with several laser diode chips (31, 32, 33) encapsulated in the housing (2), wherein - the housing (2) comprises a cover plate (23) and / or a side wall (20) which is transparent to laser radiation (41, 42, 43) generated during operation, - the cover plate (23) and / or the side wall (20) has a light emission surface (24) with adjacent emission areas (61, 62, 63), - each of the exit areas (61, 62, 63) is assigned to exactly one of the laser diode chips (31, 32, 33), - a light emission plane (26) is arranged downstream of the light emission surface (24) in a beam path, and - the cover plate (23) and / or the side wall (20) have different mean thicknesses in the exit areas (61, 62, 63) so that the optical path length for the laser radiation (41, 42, 43) of all laser diode chips (31, 32, 33) to the light exit plane (26) is the same with a tolerance of at most 3 µm. [2] Semiconductor laser (1) according to the preceding claim, wherein the exit regions (61, 62, 63) are each planar partial surfaces of the light exit surface (24) and the exit regions (61, 62, 63) are all located in the cover plate (23), wherein the tolerance within which the optical path lengths are equal is at most 1.5 µm. [3] Semiconductor laser (1) according to any one of the preceding claims, in which the laser diode chips (31, 32, 33) are edge-emitting semiconductor laser chips, wherein during operation the laser diode chips (31, 32, 33) emit light in a direction parallel to the light emission plane (26), and wherein at least one deflection optic (51) is arranged downstream of the laser diode chips (31, 32, 33) in the housing (2), which is configured to deflect laser radiation (41, 42, 43) generated during operation towards the cover plate (23). [4] Semiconductor laser (1) according to any one of the preceding claims, in which the housing (2) further comprises a base plate (21) and a middle part (22), wherein the base plate (21), the middle part (22) and the top plate (23) are attached to each other by means of anodic bonding and / or soldering, so that the laser diode chips (31, 32, 33) are hermetically sealed in the housing (2), and wherein the middle part (22) and the top plate (23) are made of the same material. [5] Semiconductor laser (1) according to the two preceding claims, in which the middle part (22) is attached between the base plate (21) and the top plate (23), and wherein the central part (22) comprises exactly one deflecting optic (51) as a flat, inclined boundary surface of a recess and the laser diode chips (31, 32, 33) are arranged in the recess of the central part (22). [6] Semiconductor laser (1) according to any one of the preceding claims, where the thickness of the cover plate outside the exit areas (61, 62, 63) is between 0.2 mm and 2 mm inclusive, wherein a thickness reduction in at least one of the exit areas (61, 62, 63) is at least 0.1 mm. [7] Semiconductor laser (1) according to any one of the preceding claims, where the top plate (23) and / or the side wall (20) is made of glass, wherein a refractive index of the cover plate (23) and / or the side wall (20) for the laser radiation (41, 42, 43) generated during operation at a temperature of 300 K is between 1.4 and 1.6 inclusive. [8] Semiconductor laser (1) according to one of the preceding claims, wherein the exit regions (61, 62, 63) have different shapes in plan view of the light exit surface (24) and / or in cross-section through the light exit surface (24). [9] Semiconductor laser (1) according to one of the preceding claims, wherein at least one of the exit regions (61, 62, 63) is oriented obliquely to the light exit plane (26), wherein an angle between the light exit plane (26) and the relevant exit region (61, 62, 63) is between inclusive 0.5° and 5°. [10] Semiconductor laser (1) according to any one of the preceding claims, where a light entry surface (25) of the top plate (23) and / or the side wall (20) is flat, wherein the light entry surface (25) is opposite the light exit surface (24) and the distance of the laser diode chips (31, 32, 33) to the light entry surface (25) along a beam path is between inclusive 0.3 mm and 3 mm. [11] Semiconductor laser (1) according to any one of the preceding claims, in which one of the laser diode chips (31) is configured to generate red light, one of the laser diode chips (32) is configured to generate green light and one of the laser diode chips (33) is configured to generate blue light and the laser diode chips (31, 32, 33) are electrically controllable independently of each other, wherein the laser diode chips (31, 32, 33) are jointly arranged a beam shaping optic (52) and / or a movable deflecting mirror (53). [12] Semiconductor laser (1) according to any one of the preceding claims, in which the emission areas (61, 62, 63) are directly provided with at least one antireflective coating (54), wherein the emission areas (61, 62, 63) are arranged along a straight line when viewed from above the light emission plane (26), and where the mean roughness of the exit areas (61, 62, 63) is at most 0.2 µm. [13] Semiconductor laser (1) according to one of claims 1 or 6 to 12, wherein the exit regions (61, 62, 63) are all located in the side wall (20). [14] Manufacturing process for a semiconductor laser (1) according to any one of the preceding claims comprising the steps: A) Providing the housing (2), preferably with the laser diode chips (31, 32, 33) already encapsulated therein, B) Operating the laser diode chips (31, 32, 33) and measuring a radiation characteristic of each of the laser diode chips (31, 32, 33), C) Modifying the top plate (23) and / or the side wall (20) in the exit areas (61, 62, 63) so that positioning tolerances of the laser diode chips (31, 32, 33) in the housing (2) are compensated and the optical path length for the laser radiation (41, 42, 43) of all laser diode chips (31, 32, 33) to the light exit plane (26) is equal with a tolerance of at most 3 µm and / or is equal with a tolerance of at most 3 µm to a previously specified target value. [15] Manufacturing method according to the preceding claim, wherein in step C) material is removed from the cover plate (23) and / or from the side wall (20) such that the cover plate (23) and / or the side wall (20) becomes thinner in at least one of the exit areas (61, 62, 63) than next to the exit areas (61, 62, 63). [16] Manufacturing method according to the preceding claim, wherein the material removal is carried out by means of laser ablation and / or by means of laser-induced structural modification within the cover plate (23) and / or within the side wall (20) and subsequent etching. [17] Manufacturing method according to one of claims 14 to 16, wherein after step C) at least one of the exit areas (61, 62, 63) is smoothed by laser polishing.

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