Semiconductor laser and method for manufacturing semiconductor laser

Abstract

In an embodiment, a semiconductor laser (1) comprises a housing (2) in which a plurality of laser diode chips (31, 32, 33) are encapsulated. The housing (2) comprises a cover plate (23) and / or a side wall (20), which are permeable to the generated laser radiation (41, 42, 43). The cover plate (23) and / or the side wall (20) have a light exit surface (24) with exit regions (61, 62, 63) arranged side by side. Each exit region (61, 62, 63) is associated with exactly one of the laser diode chips (31, 32, 33). A light exit plane (26) is arranged downstream of the light exit surface (24). The cover plate (23) and / or the side wall (20) have different average thicknesses in the exit regions (61, 62, 63) so that the optical path lengths of the laser radiation of all laser diode chips (31, 32, 33) to the light exit plane (26) are equal and have a tolerance of at most 1.5.

Description

Technical Field

[0001] The present invention provides a semiconductor laser and a method for manufacturing the semiconductor laser. Background Art

[0002] The object to be achieved is to specify a semiconductor laser which can be produced efficiently and which emits radiation having defined optical characteristics.

[0003] The object is achieved, among other things, by a semiconductor laser and by a production method having the features of the independent claims. Preferred developments are the subject matter of the dependent claims. Summary of the invention

[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 metal carrier such as a molybdenum plate. Furthermore, the housing preferably comprises at least one transparent material such as a glass and / or sapphire sheet. Furthermore, the housing can contain plastic. Hermetic means that no exchange of microscopic substances such as oxygen or water vapor can occur between the interior and the exterior of the housing. Hermetic sealing means, for example, a permeability of up to 5×10 -9 Pam / s, especially at room temperature.

[0005] According to at least one embodiment, the housing includes one or more laser diode chips. At least one laser diode chip is arranged and sealed in the housing. In particular, the laser diode chip is located in a recess in the housing.

[0006] According to at least one embodiment, the housing comprises a cover plate. The cover plate is at least partially permeable to the laser radiation generated during operation. The cover plate can be made of a separate, homogeneous material. Alternatively, the cover plate comprises a region permeable to the laser radiation, which region can be embedded in a further material, wherein the further material does not need to be permeable to the laser radiation. A window is provided on the cover plate, through which the laser radiation can be emitted. The cover plate contains a light exit surface for the laser radiation generated during operation.

[0007] Preferably, the cover plate forms a cover of the housing, wherein the cover plate can close a recess of the housing. The laser diode chip is preferably mounted at the bottom of the recess so that the cover plate can be arranged spaced apart from the laser diode chip. Therefore, the cover plate is preferably different from the mounting platform of the laser diode chip.

[0008] According to at least one embodiment, the light exit surface includes exit areas for laser radiation arranged side by side. In a top view of the light exit surface, the exit areas preferably do not overlap. The distance between adjacent exit areas is, for example, at least 0.1 mm, 0.4 mm, or 1 mm.

[0009] Instead of the cover plate, the side wall of the housing can serve as an exit window for the generated laser radiation. The light exit surface with the exit regions arranged side by side is located in the side wall, in particular on the outside of the side wall. In addition, it is possible to distribute the light exit surface with the exit regions arranged side by side on one or more side walls and on the cover plate. If the side wall comprises at least one exit region, the embodiments of the cover plate given above and below also apply to the side wall.

[0010] Furthermore, the substrate can also have the function of a cover plate on which the laser diode chip is mounted. In this case, the features of the cover plate also apply to the substrate accordingly.

[0011] According to at least one embodiment, each exit region is assigned exactly one of the laser diode chips. There is preferably a 1:1 assignment between exit regions and laser diode chips.

[0012] According to at least one embodiment, in the beam path, the light exit plane is arranged downstream of the light exit surface. After passing through the light exit surface, the light exit plane is preferably oriented perpendicular to the emission direction of the laser diode chip. It is feasible that the light exit surface is at least located in the light exit plane of the area outside the exit area.

[0013] According to at least one embodiment, the cover plate has different average thicknesses in the exit region. That is, the cover plate is thinner in at least one exit region than in at least another exit region. Due to the different cover plate thicknesses in the exit region, the optical path lengths of the laser radiation of all laser diode chips to the light exit plane are equal. Equal means, in particular, that the difference in the optical path length is at most 3 μm or 1.5 μm or 1 μm. In addition, the angular tolerance of the corresponding laser radiation (for example to the light exit plane) is preferably at most 2° or 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 comprises a cover plate and / or side walls, which are permeable to the laser radiation generated during operation. The cover plate and / or the side walls have a light exit surface with exit regions arranged side by side. Each exit region is associated with exactly one of the laser diode chips. In the beam path, the light exit plane is arranged downstream of the light exit surface. The cover plate and / or the side walls have different average thicknesses in the exit region, so that the optical path lengths of the laser radiation of all laser diode chips to the light exit plane are the same with a tolerance of up to 3 μm or 1.5 μm.

[0015] When a plurality of laser light sources are combined, such as laser diodes, with the goal of combining the radiation of the individual laser light sources into one point, it is advantageously possible to use a common optical element for focusing. The focal plane of the optical element is determined by the optical path length between the relevant laser light source and the optical element. Here, the optical path length needs to be adjusted with high precision for all laser light sources, so that the light source has the same distance from the optical element for all focusing points. In addition, it may be necessary to adjust the direction of the beam axis of the light source with high precision.

[0016] For this purpose, it is usually necessary to position the laser light source with high precision. If the laser diode is mounted on a base, a so-called subassembly, the subassembly must also be mounted with high precision in the housing. If additional optical elements are integrated in the housing, these must also be mounted with high precision. Furthermore, it can also be meaningful to precisely adjust the direction of the beam axis in addition to the optical path in order to simplify the assembly of the downstream connected optics. This applies equally to semiconductor lasers with only one laser diode chip and with a plurality of laser diode chips.

[0017] Since it is difficult to identify the laser facets exactly, the required high-precision passive placement of the components without operating the laser light source is usually problematic. Helpfully, the use of metallization of the laser diode as an orientation point is usually not feasible, since such metallization is not arranged accurately enough at the facets. In addition, high-precision placement of the laser diode or the optical component is relatively slow and therefore expensive. Furthermore, conventional active placement (in which the laser diode is in operation) is also relatively slow and therefore expensive.

[0018] Furthermore, laser diodes cannot be operated at soldering temperature, i.e. conditioning must be performed close to room temperature. Subsequently, the laser diode and the submount must be introduced and soldered at soldering temperature. This requires long cycle times, so that the laser diode must be kept at soldering temperature for a long time, especially when multiple laser diodes are soldered on a common submount. This generally has a negative impact on the service life of the laser diode.

[0019] The semiconductor laser described here has an optical path length adjustment according to the production method described here, wherein the path length of each beam of a laser diode chip through the window through which the radiation passes is individually varied, after which all the laser diode chips are positioned and fixed. As a result, the light cones of the individual laser diode chips should be in the window and, in particular, should not overlap at the light exit surface.

[0020] Thus, the optical path can be adjusted individually for each laser diode chip in the region of the radiation transmission by local changes in the thickness or refractive index of the window. In addition, by local changes in the orientation of the light exit surface, the beam direction can be influenced and adjusted individually by light refraction in the exit region.

[0021] For example, path length adaptation and / or surface adaptation can be achieved by local laser ablation of the window in the exit region of the penetrating radiation. In this case, the window, i.e. the cover plate, can have a high refractive index in order to achieve a large influence on the optical path length with a small ablation depth. Alternatively, it is possible to locally change the properties of the window in the case of a window made of glass by laser radiation, so that the etchability of the material of the window is locally increased. In a further step, the window is etched, wherein the material of the window is preferably ablated in the exit region.

[0022] The thickness of the window is thus reduced locally and the orientation of the surface is controllable. Furthermore, it is possible that the window, for example made of glass, has its refractive index changed locally by laser radiation and thus the optical path while the thickness remains constant.

[0023] Furthermore, it is possible to apply locally limited material to the cover plate, for example by laser sintering. In this case, the applied material preferably has a high refractive index in order to achieve large differences in optical path lengths with thinly applied layers.

[0024] This method allows the path length differences between the laser diode chip and the light exit plane to be adjusted and compensated. Therefore, the optical path lengths of all laser diode chips are measured beforehand. For the laser diode chips with the smallest or largest path lengths, preferably no processing of the cover plate takes place. For the other light sources, the cover plate is processed in order to adjust the optical path length to the desired value.

[0025] It is possible to minimize the path length differences. Alternatively, the path length differences can be adjusted to a target value, for example in order to compensate for chromatic aberrations of a downstream optical system in advance. Furthermore, it is possible to process the material of the cover plate in all emission regions in order to adjust the optical path lengths of all laser diode chips to a preset target value.

[0026] Since the housing can be installed and closed before the cover plate is processed, the laser diode chips can be operated in order to directly measure the focus position and / or the beam direction of each laser diode chip and thus determine the required removal or coating of material in the emission region. Furthermore, the focus position and / or the beam direction can also be measured simultaneously during the processing of the cover plate in order to thus directly control the process of the processing of the cover plate.

[0027] For the semiconductor laser described here, the requirements for the assembly precision of the laser diode chip and the optical elements are significantly reduced, which can reduce the equipment expenditure and increase the processing speed. This is cost-effective and reduces the temperature load on the laser diode chip during soldering.

[0028] In contrast, in conventional methods, a plurality of components must be assembled individually with high precision, since the target value, in particular the focus position, is dependent on the accumulated assembly tolerances. In contrast, in the production method described here, the accumulated assembly tolerances of all components are compensated together after assembly. In the conventional passive placement of the components, only the physical path can be controlled, wherein the physical path can only indirectly determine the focus position. In contrast, in the method described here, the focus position and / or the beam direction, i.e. the target value, can be directly measured and adjusted.

[0029] In conventional methods, each semiconductor laser must be processed precisely at great expense, and those semiconductor lasers that do not meet the technical specifications due to faults or process fluctuations must be processed precisely. The production method described here makes it possible to test semiconductor lasers at an early stage and, if necessary, to sort them out before the complex processing of the cover plate.

[0030] According to at least one embodiment, a plurality of exit regions or at least one exit region or a majority of the exit regions are flat partial surfaces of the light exit surface, that is, at least one relevant exit region has no or no significant curvature for the laser radiation.

[0031] Alternatively, it is possible that at least one or all of the exit regions have a defined curvature. Such a curvature can, for example, adjust the beam profile of the relevant laser radiation or achieve a focusing or diverging effect. In other words, the shaped exit region can be similar to a condenser or a correction optical element.

[0032] According to at least one embodiment, the laser diode chip is an edge-emitting semiconductor laser chip. The active region of the laser diode chip is preferably oriented parallel or approximately parallel to the light exit plane in this case. Thus, the emission of the laser radiation of the laser diode chip parallel to the active region, that is to say parallel or approximately parallel to the light exit plane, is achieved. Approximately means, for example, an angular tolerance of at most 5° or 2° or 1°.

[0033] Alternatively, the laser diode chip can also be a surface emitting laser chip which emits vertically or approximately vertically to the light exit plane. Furthermore, it is possible to mount an edge emitting semiconductor laser chip in a housing so that emission is achieved vertically or approximately vertically to the light exit plane.

[0034] According to at least one embodiment, one or more deflection optical elements are arranged in the housing. The at least one deflection optical element is thus provided for deflecting the laser radiation generated during operation towards the cover plate, in particular in a direction perpendicular or approximately perpendicular to the light exit plane. For example, the deflection optical element is a 45° mirror. The deflection optical element is preferably shaped to be reflective and flat.

[0035] According to at least one embodiment, the housing comprises a base plate. Furthermore, the housing optionally comprises an intermediate portion, wherein such intermediate portion is located between the base plate and the cover plate.

[0036] According to at least one embodiment, the base plate and the cover plate and the optional intermediate part are connected to each other by anodic bonding and / or by welding. Alternatively or additionally, other connection technologies such as gluing or wafer bonding are also conceivable for the connection of the base plate, the cover plate and the optional intermediate part. The laser diode chip is thus hermetically encapsulated in the housing.

[0037] According to at least one embodiment, the middle part and the cover plate are made of the same material. For example, glass is used. The middle part and the cover plate are preferably fixed to each other by anodic pressure welding. The substrate is made of a semiconductor material, such as silicon. Alternatively, the substrate can be a circuit board, for example, made of a ceramic material or based on a metal, such as a metal core board.

[0038] According to at least one embodiment, the middle part comprises a deflection optical element. In this case, preferably there is exactly one deflection optical element, which deflects all laser beams of the laser diode chip toward the cover plate as an inclined interface of the recess of the middle part. In this case, the laser diode chip is preferably arranged in the housing, in particular in the recess of the middle part.

[0039] According to at least one embodiment, the thickness of the cover plate at least outside the exit region is at least 0.1 mm or 0.2 mm or 0.3 mm. Alternatively or additionally, the thickness of the cover plate is at most 2 mm or 1 mm or 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 exit region is at least 30 μm or 50 μm or 0.1 mm or 0.14 mm, or the cover plate is configured for such a thickness reduction or a maximum thickness reduction. The thickness reduction that is actually achieved or that is feasible is relatively large in relation to the thickness of the cover plate. For example, in at least one exit region, the thickness reduction is at least 20% or 35% or 50% of the thickness of the cover plate outside the exit region and / or at most 80% or 70% of the thickness of the cover plate, or such a thickness reduction is achievable.

[0041] Depending on the accuracy of the statistical variations in the placement of the laser diode chips in particular, it is possible that for some semiconductor lasers only a relatively small thickness reduction is required in the exit region in order to obtain the desired optical path length with the required accuracy. For example, the maximum thickness change in one of the exit regions or in all exit regions only needs to be a minimum of 3 μm or 20 μm.

[0042] The foregoing only details a thickness reduction. The same values ​​apply analogously to a thickness increase by material application and to a change in the optical path length by means of a refractive index change without a geometric thickness change.

[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 cover plate made of glass, the refractive index is preferably between 1.4 and 1.6 inclusive. The values ​​for the refractive index are suitable for 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, in a top view of the light exit surface and / or in a cross section through the light exit surface, the exit area has different shapes. For example, in a top view, the exit area is shaped as a rectangle, an ellipse or a circle. In a cross section, the exit area is preferably a straight line segment or also a curved segment in the shape of a circular arc or a hyperbola.

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

[0046] According to at least one embodiment, the cover plate has a light incident surface. The light incident surface is arranged opposite to the light exit surface. The light incident surface is preferably flat. The light incident surface can have an optically effective coating, such as an anti-reflection coating.

[0047] According to at least one embodiment, the optical distance of the laser diode chip to the light entry surface along the beam path of the corresponding laser radiation is at least 0.2 mm or 0.3 mm or 0.5 mm. Alternatively or additionally, the optical distance is at most 3 mm or 2 mm or 1.5 mm. In other words, the light entry surface is optically located relatively close to the laser diode chip. In particular, the beam path is initially approximately parallel to the light entry surface and then, starting from the optional deflection optics, 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 laser diode chip is provided for generating red light, at least one laser diode chip is provided for generating green light and at least one laser diode chip is provided for generating blue light. Preferably, the laser diode chips can be electrically driven independently of one another.

[0049] Furthermore, it is possible for further laser diode chips to be present which emit radiation in the invisible spectral range, for example laser diode chips for generating near-ultraviolet radiation and / or for generating near-infrared radiation.

[0050] According to at least one embodiment, the beam shaping optics and / or the movable deflection mirror are arranged together downstream of the laser diode chip. The beam shaping optics and / or the movable deflection mirror are preferably located outside the housing. Such beam shaping optics and / or the movable deflection mirror can be accommodated in another housing, in which the housing of the semiconductor laser with the laser diode chip is also located.

[0051] According to at least one embodiment, at least one exit area or all exit areas of the cover plate are directly provided with one or more anti-reflection coatings. At least one anti-reflection coating can extend continuously through the light exit surface or be limited to the exit area or a corresponding specific exit area.

[0052] According to at least one embodiment, the exit regions are arranged along a straight line in a top view of the light exit plane. In particular, the optical midpoint, ie, the intersection point of the optical axis through the exit regions is arranged on a straight line.

[0053] According to at least one embodiment, the average roughness of the exit region is at most 0.3 μm or 0.2 μm or 0.1 μm or 0.05 μm or 0.02 μm. The exit region is thus formed relatively flat.

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

[0055] In at least one embodiment, the method comprises the following steps, preferably in the order given:

[0056] A) providing a housing, preferably with a laser diode chip already encapsulated therein,

[0057] B) operating the laser diode chips and measuring the emission characteristics of each laser diode chip,

[0058] C) Changing the cover plate and / or the side walls in the exit region such that position tolerances of the laser diode chips in the housing are corrected and the optical path lengths of the laser radiation of all laser diode chips up to the light exit plane are identical with a tolerance of at most 3 μm or at most 1.5 μm and / or the optical path lengths are identical to a previously preset target value with a tolerance of at most 3 μm or at most 1.5 μm.

[0059] Instead of packaging the laser diode chip already before operation and measurement, it is possible to operate and measure the laser diode chip, in particular in a vacuum or in a protective gas pressure. Afterwards, the cover plate can be processed as a separate part and is independent of other components of the semiconductor laser. After processing, the cover plate is then applied to at least one remaining component of the housing, so that the laser diode chip is packaged only after the emission region is produced. This is particularly advantageous if the processing of the cover plate could damage other components of the semiconductor laser, such as optics or the laser diode chip.

[0060] According to at least one embodiment, material removal from the cover plate is carried out in step C). Thus, the cover plate in at least one exit region is thinner than the cover plate next to the exit region. Alternatively, a material coating is applied so that the cover plate is thicker in the relevant exit region than in the area next to the exit region.

[0061] In accordance with at least one embodiment, the material removal is effected by means of laser ablation and / or by means of laser-induced structural changes in combination with subsequent etching.

[0062] As an alternative to material removal or in addition to material addition, the geometric thickness of the cover plate can remain constant, wherein the optical thickness is changed by varying the material of the cover plate, that is, the refractive index of the material of the cover plate is locally changed, for example by means of laser radiation.

[0063] According to at least one embodiment, after step C), a smoothing of the light exit surface is achieved in at least one exit region. This smoothing is preferably achieved by means of laser polishing. Thus, irregularities and roughness of the light exit surface in the exit region are reduced or eliminated. These roughnesses are produced, for example, by laser ablation. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] The semiconductor laser described herein and the manufacturing method described herein are further explained below with reference to the accompanying drawings according to the embodiments. Here, the same elements in the various drawings have the same reference numerals. However, the drawings are not shown to scale, but individual elements can be exaggerated for better understanding.

[0065] The accompanying drawings show:

[0066] Figure 1shows a schematic perspective view of an embodiment of a semiconductor laser described herein,

[0067] Figures 2 to 4 shows a schematic cross-sectional view of an exemplary embodiment of a semiconductor laser described herein,

[0068] Figure 5 shows a schematic perspective view of a cover plate of a semiconductor laser described herein,

[0069] Figures 6 to 8 shows the calculation of the path length difference for the semiconductor laser described herein,

[0070] Fig. 9 shows a schematic cross-sectional view of an exemplary embodiment of a semiconductor laser described herein,

[0071] Fig.10 and Fig.11 shows the calculation of the inclination of the exit region of the semiconductor laser described here,

[0072] Fig.12 and Fig.13 shows a schematic cross-sectional view of an exemplary embodiment of a semiconductor laser described herein,

[0073] Figures 14 to 18 A schematic cross-sectional view showing the steps of the method for manufacturing a semiconductor laser described herein, and

[0074] Fig.19 A schematic cross-sectional view of an exemplary embodiment of a semiconductor laser described here is shown. DETAILED DESCRIPTION

[0075] exist Figure 1 1 shows an embodiment of a semiconductor laser 1. The semiconductor laser 1 comprises three laser diode chips 31, 32, 33, which are preferably configured to generate red, green and blue light. The laser diode chips 31, 32, 33 are optionally arranged on an intermediate carrier 30. Such an intermediate carrier 30 can also be denoted as a submount. The laser diode chips 31, 32, 33 are edge-emitting laser chips.

[0076] The laser diode chips 31, 32, 33 are located in the housing 2. The housing 2 consists of a base plate 21, a middle part 22 and a cover plate 23. The base plate 21 and the middle part 22 are joined to each other in a gas-tight manner via a welding connection 27. The connection between the cover plate 23 and the middle part 22 is preferably achieved without adhesive via anodic bonding. The middle part 22 and the cover plate 23 are preferably made of glass and are transparent to the laser radiation 41, 42, 43 generated during operation. The laser diode chips 31, 32, 33 are therefore located in the recess 28 of the middle part 22.

[0077] exist Figure 2 It is shown in Figure 1 1 . The laser diode chips 31, 32, 33 emit laser radiation 41, 42, 43 in a direction parallel to the light exit plane 26. Furthermore, the light exit plane 26 extends into the light exit surface 24 of the cover plate 23. At the deflection optics 51, the laser radiation 41, 42, 43 is deflected in the direction of the cover plate 23. The laser radiation 41, 42, 43 enters the cover plate 23 via the planar light entry surface 25.

[0078] Furthermore, the cover plate 23 has a plurality of emission regions 61, 62, 63 for the respective laser diode chips 31, 32, 33 in the light emission surface 24. The emission regions 61, 62, 63 are arranged Figure 1 In the representation by an ellipse, Figure 2 In the top view of the light exit surface 24, the exit regions 61, 62, 63 are close to each other. In the exit regions 61, 62, 63, a correction of the optical path length of the laser radiation 41, 42, 43 is achieved.

[0079] The correction for the optical path length is Figure 3 and Figure 4 The Figure 3 In the figure, the cover plate 23 is in its initial position, no modifications are shown and the exit areas 61, 62, 63 are basically not shown. Figure 4 It is inferred that the cover plate 23 has different thicknesses in the exit regions 61, 62, 63. The different thicknesses and the different refractive index of the cover plate 23 compared to the surroundings allow a desired correction of the optical path length between the laser diode chip (not shown) and the light exit plane 26 to be achieved.

[0080] In the region of the cover plate 23 in which the cover plate 23 still has the original thickness, the light exit plane 26 is located in the light exit surface 24. Furthermore, the light exit plane 26 can be at least partially an imaginary plane, which is oriented in particular perpendicular to the main emission direction of the laser diode chip. The exit region 62 is located in the light exit plane 26, in which the cover plate 23 does not change. Figure 5 , a completed cover plate 23 without the remaining components of the semiconductor laser 1 is shown by way of example. It can be seen that the exit regions 61, 62 have different basic shapes when viewed from above the light exit surface 24. The same can also apply to all other embodiments.

[0081] Figure 5The cover plate 23 can be manufactured separately from the other components of the housing 2. Thus, for example, the laser diode chips 31, 32, 33 are operated and measured in a protective gas pressure. The correction data obtained from the measurement are used to process the cover plate 23 or at least partially process it.

[0082] The at least partially processed cover plate 23 is then used to close the housing 2. If necessary, a readjustment of the exit regions 61, 62, 63 can also be achieved by re-running and measuring the laser diode chips 31, 32, 33 and re-processing the exit regions 61, 62, 63 when the cover plate 23 has already been applied.

[0083] If the cover plate 23 is processed only separately from other components of the semiconductor laser 1, then the exit regions 61, 62, 63 can also be located at the light incident surface instead of necessarily being located at the light exit surface. The features of the light exit surface described above are correspondingly applicable to the light incident surface. This also applies to all other embodiments.

[0084] exist Figure 6 Schematic diagram and Figure 7 and Figure 8 The associated calculations illustrate how the thickness correction in the exit regions 62, 63 can be achieved, by way of example for two laser diode chips 32, 33 with laser radiation 42, 43. The laser diode chips 32, 33 are located in the gas or vacuum region of a recess 28, which has a refractive index n of 1 or approximately 1. In this region, the distance traveled by the laser radiation 43 in the air is x a .

[0085] The index a represents air, which is called air in English. g The medium passing through the cover plate 23 is, for example, glass with a refractive index n of 1.5. The index g corresponds to the glass.

[0086] exist Figure 7 As can be seen in FIG. 1 , the path length difference Δx in the groove 28 varies according to the thickness variation of the cover plate 23 in the relevant exit region 62. a Dividing by the refractive index n-1 gives the path length difference Δx of the laser radiation 42 g The refractive index of the cover plate 23 is about 1.5, which means that the thickness correction Δx g corresponds approximately to the optical path length difference Δx in the groove 28 a twice as much.

[0087] exist Figure 8 An evaluation of the required accuracy for the design of the thickness of the cover plate 23 in the exit regions 61, 62, 63 is shown in FIG. The permissible tolerance Δx of the thickness of the cover plate 23 is gIt is related to the permissible tolerance of the optical path length Δp and the refractive index n of the cover plate. For example, if the permissible error of the optical path length Δp is 1.5 μm and the refractive index n of the cover plate 23 is 1.5, the resulting thickness fluctuation Δx g The tolerance is 3μm.

[0088] If the laser diode chips 31, 32, 33 have, for example, an assembly tolerance of + / -10 μm, then the maximum difference in the optical path relative to the deflection optics 51 is 20 μm. In order to compensate for the maximum tilt angle α occurring, for example, of 4°, the path length difference would need to be approximately 50 μm. The optical path length to be corrected is therefore approximately 70 μm. This results in a maximum change in the thickness of the cover plate 23 of 140 μm at a refractive index of 1.5. If the refractive index of the cover plate 23 is, for example, 1.8, then the required change in the thickness of the cover plate 23 is only approximately 90 μm.

[0089] The path length x in the groove 28 a For example, it is about 0.5 mm. The thickness x of the cover plate 23 g , ie the initial thickness of the cover plate 23 is, for example, 200 μm. This results in a total optical path length of approximately 800 μm to the light exit plane 26, which is modified to approximately 70 μm, ie approximately 10%.

[0090] exist Fig. 9 4 shows that the exit regions 41, 42, 43 not only have different thicknesses, but are also arranged obliquely to the light exit plane 26. The oblique exit regions 61, 62 enable the exit angle of the laser radiation 41, 42, 43 to be modified. Fig. 9 The laser radiation 41 , 42 , 43 is schematically shown in FIG.

[0091] In order to achieve the required angle correction, Fig.10 and Fig.11 The calculation of the inclination angle γ of the exit regions 61 , 62 , 63 is explained in detail in . Here, S1 denotes the light entrance surface 25 , and S2 denotes the associated exit region 61 , 62 , 63 .

[0092] For the refractive index n of the cover plate 2 2 The angle γ of the corresponding exit regions 61, 62, 63 is 2.4° when the angle α to be corrected is 1.5°. If the angle α to be corrected is 1.5°, the correction angle γ is approximately 1.2°. The desired angular tolerance is preferably a maximum of 1°, and the laser radiation 41, 42, 43 obtained and corrected by the cover plate 23 with this angular tolerance is perpendicular to the light exit plane.

[0093] exist Fig.12A further embodiment of a semiconductor laser 1 is illustrated in FIG. The groove 28 is produced directly in the substrate 21. In addition, a separate deflection optical element 51 is present. The light entry surface 25 can be curved and can be shaped, for example, as a focusing lens. A low roughness 29 of, for example, up to 100 nm can be present at the light exit surface 24 in the exit regions 61, 62, 63. This is combined with Fig.12 The mentioned variants may also be present in all other exemplary embodiments, either individually or in any combination.

[0094] exist Fig.13 In the embodiment of the present invention, a common light beam is arranged downstream of all laser diode chips 31, 32, 33 of the semiconductor laser 1 via an optical element 52 and a common movable deflection mirror 53. Thus, optical elements 52, 53 are provided for all laser radiation 41, 42, 43. The components 1, 52, 53 can be integrated in another common housing (not shown).

[0095] For example, Fig.13 Components 1, 52, and 53 are structural components of VR glasses or AR glasses, wherein VR stands for virtual reality and AR stands for augmented reality, i.e., extended reality.

[0096] exist Figures 14 to 17 A method for manufacturing an embodiment of a semiconductor laser 1 is explained by way of example in FIG. Fig.14 , providing and temporarily operating laser diode chips 31, 32, 33 encapsulated in housing 2. An analysis of the optical path length and / or the emission direction and / or the beam profile of the laser radiation 41, 42, 43 is achieved via optical measuring optics 82 and via camera 81. Based on this measurement, it is calculated how to design the subsequent exit regions 61, 62, 63.

[0097] exist Fig.15 The ablation of material of the cover plate 23 by means of a laser beam 71 is explained in FIG.

[0098] Fig.14 and 15 The steps in can be performed iteratively, or Fig.15 Steps and Fig.14 The steps occur simultaneously, so that the laser diodes 31 , 32 , 33 can be operated during the processing of the cover plate 23 and the material removal can be actively controlled.

[0099] exist Fig.16 In the optional step of , it is shown that the surface for the exit region, produced, for example, by laser ablation, has a roughness 29. Laser polishing and thus smoothing can be achieved by means of a laser beam 23, in particular infrared laser radiation.

[0100] See Fig.17, thus producing smooth exit areas 61, 62, 63. The exit areas 61, 62, 63 can optionally be provided with an anti-reflection coating 54. Here, a common anti-reflection coating can exist or a separate anti-reflection coating can be applied. The anti-reflection coating 54 can extend over the entire light exit surface 24, or can be only partially arranged in the relevant exit areas 61, 62, 63.

[0101] exist Fig.18 An alternative method for shaping the exit regions 61, 62, 63 is shown in FIG. With the aid of a laser beam 72, structural changes in the material are achieved in the cover plate 23, wherein the desired geometry of the exit regions 61, 62, 63 is defined. These material changes can be etched away by subsequent etching (not shown) to produce the exit regions 61, 62, 63. This method is also referred to as invisible cutting.

[0102] In addition, Fig.18 , a variant is shown in which a recess 28 is present in the cover plate 23. The base plate 21 can thus be designed to be flat and the middle part can be omitted. Furthermore, it is possible that the laser diode chips 31, 32, 33 are surface-emitting laser diode chips or edge-emitting laser diode chips, which emit approximately perpendicularly to the direction of the light entry surface 25. This variant can be present alone or in combination in all other exemplary embodiments.

[0103] and Fig.15 and Fig.18 In contrast to the method steps in the embodiment of the present invention, additional material can be applied to the cover plate 23, for example by laser sintering, so that the local thickness is increased. In addition, alternatively or additionally, it is possible to achieve a change in the local refractive index in the cover plate 23, so that the geometric thickness of the cover plate 23 does not need to be changed.

[0104] In the above figures, the thickness variations of the emission regions 61, 62, 63 are respectively realized in the cover plate 23 of the housing 2. Fig.19 In the embodiment of the invention, there is no targeted thickness variation, but rather the side wall 20 is provided with the exit regions 61, 62, 63. The optical thickness of the side wall 20 is thus locally changed in order to achieve a correction of the optical path length and / or the emission direction. In this arrangement, the deflection optics can be omitted. The side wall 20 is preferably designed in one piece with the middle part 22.

[0105] The above-listed features of the exit regions 61, 62, 63 in the cover plate 23 are also applicable to the exit regions 61, 62, 63. Fig.19 Located in the side wall 20 .

[0106] This patent application claims the priority of German patent application 10 2018 129 346.1, the disclosure of which is incorporated herein by reference.

[0107] The invention described here is not limited to the description based on the exemplary embodiments. Rather, the invention includes every new feature and every combination of features, which includes every combination of features in particular in the claims, including when these features or combinations themselves are not explicitly presented in the claims or exemplary embodiments.

[0108] Reference Numbers List

[0109] 1 Semiconductor Laser

[0110] 2 Housing

[0111] 20 Sidewall

[0112] 21 substrate

[0113] 22 Middle part

[0114] 23 Cover

[0115] 24 Light emission area

[0116] 25 Light incident area

[0117] 26 Light exit plane

[0118] 27 Welding connection

[0119] 28 grooves

[0120] 29 Roughness

[0121] 30 Intermediate carrier

[0122] 31 Red laser diode chips

[0123] 32 Green laser diode chips

[0124] 33 Blue laser diode chips

[0125] 34 Welding wire

[0126] 41 Red laser radiation

[0127] 42 Green Laser Radiation

[0128] 43 Blue Laser Radiation

[0129] 51 Deflection optics

[0130] 52 Beam Shaping Optics

[0131] 53 Movable deflecting mirror

[0132] 54 Anti-reflective coating

[0133] 61 Red light emission area

[0134] 62 Green light emission area

[0135] 63 Blue light emission area

[0136] 71 Laser beam for ablation

[0137] 71 Laser beams for structural changes

[0138] 73 Laser beam for laser polishing

[0139] 81 Camera

[0140] 82 Measuring optics.

Claims

1. A semiconductor laser (1), comprising a housing (2) and a plurality of laser diode chips (31, 32, 33), wherein the laser diode chips are packaged in the housing (2), wherein: the housing (2) comprises a cover (23) and / or a side wall (20) which is permeable to the laser radiation (41, 42, 43) generated during operation, - the cover plate (23) and / or the side wall (20) has a light exit surface (24), the light exit surface having exit areas (61, 62, 63) arranged side by side with one another, - each of the exit regions (61, 62, 63) is associated with exactly one of the laser diode chips (31, 32, 33), - a light exit plane (26) is arranged downstream of the light exit surface (24) in the beam path, and - the cover plate (23) and / or the side wall (20) have different average thicknesses in the emission regions (61, 62, 63), so that all the laser diode chips (31, The optical path lengths of the laser radiation (41, 42, 43) of the optical transmission lines (32, 33) to the light exit plane (26) are all equal and have a tolerance of at most 3 μm.

2. The semiconductor laser (1) according to claim 1, wherein: The exit regions (61, 62, 63) are respectively flat partial surfaces of the light exit surface (24), and all of the exit regions (61, 62, 63) are located in the cover plate (23). Therein, the tolerance is at most 1.5 μm, within which the optical path lengths are equal.

3. The semiconductor laser (1) according to claim 1, in, The laser diode chips (31, 32, 33) are edge-emitting semiconductor laser chips. wherein, during operation, emission of the laser diode chips (31, 32, 33) is achieved in a direction parallel to the light emission plane (26), and In the housing (2), at least one deflection optical element (51) is arranged downstream of the laser diode chip (31, 32, 33), the deflection optical element (51) being provided for deflecting the laser radiation (41, 42, 43) generated during operation toward the cover plate (23).

4. The semiconductor laser (1) according to any one of claims 1 to 3, in, 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 cover plate (23) are adjacent to each other by means of anodic bonding and / or welding, so that the laser diode chips (31, 32, 33) are hermetically sealed and packaged in the housing (2), and Wherein, the middle part (22) and the cover plate (23) are made of the same material.

5. The semiconductor laser (1) according to claim 3, in, The middle part (22) is arranged between the base plate (21) and the cover plate (23), and The central part (22) comprises exactly one deflection optical element (51) as a flat, inclined boundary surface of a groove, and the laser diode chips (31, 32, 33) are arranged in the groove of the central part (22).

6. The semiconductor laser (1) according to any one of claims 1 to 3, in, Outside the emission regions (61, 62, 63), the thickness of the cover plate is greater than or equal to 0.2 mm and less than or equal to 2 mm, The thickness reduction in at least one of the exit regions (61, 62, 63) is at least 0.1 mm.

7. The semiconductor laser (1) according to any one of claims 1 to 3, in, The cover plate (23) and / or the side wall (20) are made of glass, wherein, for the laser radiation (41, 42, 43) generated during operation, at a temperature of 300K, the refractive index of the cover plate (23) and / or the side wall (20) is greater than or equal to 1.4 and less than or equal to 1.

6.

8. The semiconductor laser (1) according to any one of claims 1 to 3, in, The emission regions (61, 62, 63) exhibit different shapes in a plan view of the light emission surface (24) and / or in a cross-sectional view through the light emission surface (24).

9. The semiconductor laser (1) according to any one of claims 1 to 3, in, 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 associated exit region (61, 62, 63) is greater than or equal to 0.5° and less than or equal to 5°.

10. The semiconductor laser (1) according to any one of claims 1 to 3, in, The light incident surface (25) of the cover plate (23) and / or the side wall (20) is flat, The light incident surface (25) is arranged opposite to the light exit surface (24), and the distance from the laser diode chip (31, 32, 33) to the light incident surface (25) along the direction of the light beam is greater than or equal to 0.3 mm and less than or equal to 3 mm.

11. The semiconductor laser (1) according to any one of claims 1 to 3, in, 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) can be electrically driven independently of one another. Therein, a beam shaping optical element (52) and / or a movable deflection mirror (53) are arranged together downstream of the laser diode chips (31, 32, 33).

12. The semiconductor laser (1) according to any one of claims 1 to 3, in, The exit regions (61, 62, 63) are directly provided with at least one anti-reflection coating (54), The emission regions (61, 62, 63) are arranged along a straight line in a top view of the light emission plane (26), and The average roughness of the emission regions (61, 62, 63) is respectively at most 0.2 μm.

13. The semiconductor laser (1) according to claim 1, in, The emission regions (61, 62, 63) are all located in the side wall (20).

14. A method for manufacturing a semiconductor laser (1) according to any one of claims 1 to 13, the method comprising the following steps: A) providing a housing (2), which preferably has a laser diode chip (31, 32, 33) encapsulated in the housing, B) operating the laser diode chips (31, 32, 33) and measuring the emission characteristics of each of the laser diode chips (31, 32, 33), C) changing the cover plate (23) and / or the side wall (20) in the emission region (61, 62, 63) so that the position tolerances of the laser diode chips (31, 32, 33) are balanced in the housing (2) and all the laser diode chips (31, The optical path lengths of the laser radiation (41, 42, 43) of the optical waveguide (32, 33) to the light exit plane (26) are all equal and have a tolerance of at most 3 μm, and / or equal to a previously preset target value with a tolerance of up to 3 μm.

15. The manufacturing method according to claim 14, in, In step C), material of the cover plate (23) and / or the side wall (20) is removed so that the cover plate (23) and / or the side wall (20) are thinner in at least one of the exit regions (61, 62, 63) than next to the exit region (61, 62, 63).

16. The manufacturing method according to claim 15, in, Material removal is carried out in the cover plate (23) and / or in the side wall (20) by means of laser ablation and / or by means of laser-induced structural changes and subsequently etching is carried out.

17. The manufacturing method according to any one of claims 14 to 16, in, According to step C), at least one of the exit regions (61, 62, 63) is smoothed by means of laser polishing.

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