Abstract:
A device for shaping laser radiation, in particular for laser radiation emitted by a laser diode bar, has at least one substrate with a plurality of refractive boundary surfaces through which the laser radiation to be produced can pass in such a way that at least two partial beams of the laser radiation, which, prior to their passage, are adjacently arranged in a first direction, are adjacently arranged after their passage through the refractive boundary surfaces in a second direction which is perpendicular to the first direction. The refractive boundary surfaces are formed at a substrate or at substrates that are connected to one another.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention: 
     The present invention relates to an apparatus for shaping of laser radiation, in particular for laser radiation which is emitted by a laser diode bar, comprising at least one substrate having a plurality of refractive boundary surfaces through which the laser radiation to be shaped can pass, such that at least two partial beams of the laser radiation which are arranged alongside one another in a first direction before they pass through the refractive boundary surfaces are arranged alongside one another in a second direction, which is at right angles to the first direction, after they pass through the refractive boundary surfaces. 
     Definitions: in the propagation direction of the light to be influenced means the mean propagation of the light, in particular when this is not a planar wave or is at least partially divergent. Unless expressly stated to the contrary, the terms light beam, partial beam or beam do not mean an idealized beam of geometric optics but a real light beam, for example a laser beam with a Gaussian profile, which does not have an infinitesimally small beam cross section, but an extended beam cross section. 
     One preferred application of the present invention is the shaping of the laser radiation from high-power laser diodes, which are manufactured as so-called laser diode bars. In these laser diode bars, a large number of individual emitters are mounted alongside one another on a heat sink in a different manner, depending on the power. The number of these individual emitters has a direct influence on the beam quality of the entire laser diode: the greater the number of individual emitters, the broader is the overall beam, and the poorer is the beam quality. 
     One apparatus of the type mentioned initially is known from European Patent EP 0 770 226 B1. The apparatuses described in this document comprise two or three substrates which are at a distance from one another and are not connected to one another on each of which two refractive surfaces are formed, which contribute to the shaping of the laser radiation. On the one hand, this means that the two or three substrates must be adjusted independently of one another, which is complex. On the other hand, the repeated entry into and exit from the substrates results in considerable losses. 
     The problem on which the present invention is based is to provide an apparatus of the type mentioned initially which can be adjusted more easily. 
     BRIEF SUMMARY OF THE INVENTION 
     According to the invention, this is achieved by an apparatus of the type mentioned initially having the characterizing features of claim  1 . The independent claims relate to preferred refinements of the invention. 
     According to claim  1 , the refractive boundary surfaces are formed on a substrate or on substrates which are connected to one another. This allows all of the refractive boundary surfaces to be moved together, thus reducing the adjustment complexity. 
     In this case, it is possible for the at least one substrate and/or the refractive boundary surfaces to be designed and arranged such that at least one of the partial beams passes through the apparatus and/or through the refractive boundary surfaces essentially without being deflected. In consequence, there are no undesirable changes to the cross section of this partial beam, and comparatively few losses. 
     It is also possible for the at least one substrate and/or the refractive boundary surfaces to be designed and arranged such that at least one of the partial beams is subject to at least one total internal reflection in the interior of the at least one substrate. This means that the at least one deflected partial beam is subject to the losses that are as small as possible on its path through the apparatus. 
     It is also possible to provide for the refractive boundary surfaces to be planar surfaces. This avoids undesirable changes to the beam profile. In particular, there is no influence on the divergence of the laser radiation. Furthermore, planar surfaces can be manufactured more easily. 
     According to one preferred refinement of the invention, the apparatus comprises a monolithic substrate on which the refractive boundary surfaces are arranged. A monolithic substrate such as this makes it possible to produce a compact apparatus of simple design, which can shape the laser radiation with low losses. 
     According to one alternative refinement of the invention, the apparatus comprises at least two substrates on which the refractive boundary surfaces are arranged, wherein the at least two substrates are connected to one another, preferably adhesively bonded. Substrates which are adhesively bonded to one another also allow the boundary surfaces to be moved together, which likewise reduces the adjustment complexity. 
     In particular, it is possible in this case to provide for the at least two substrates to have planar, in particular mutually parallel surfaces, and to preferably be in the form of cuboids. Cuboids or plane-parallel plates such as these can be manufactured easily, and therefore at low cost. 
    
    
     
       Further features and advantages of the present invention will become clear on the basis of the following description of preferred exemplary embodiments, and with reference to the attached figures, in which: 
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         FIG. 1   a  shows a perspective view of a first embodiment of an apparatus according to the invention; 
         FIG. 1   b  shows a view of the first embodiment, corresponding essentially to  FIG. 1   a , showing two partial beams; 
         FIG. 2   a  shows a perspective view of the first embodiment, rotated in comparison to  FIG. 1   a;    
         FIG. 2   b  shows a view of the first embodiment, corresponding essentially to  FIG. 2   a , showing two partial beams; 
         FIG. 3   a  shows a perspective view of the first embodiment, rotated in comparison to  FIG. 2   a;    
         FIG. 3   b  shows a view of the first embodiment, corresponding essentially to  FIG. 3   a , showing two partial beams; 
         FIG. 4   a  shows a perspective view of the first embodiment, rotated in comparison to  FIG. 3   a;    
         FIG. 4   b  shows a view of the first embodiment, corresponding essentially to  FIG. 4   a , showing two partial beams; 
         FIG. 5  shows a plan view of a laser arrangement with the first embodiment of an apparatus according to the invention; 
         FIG. 6  shows a side view of the laser arrangement shown in  FIG. 5 ; 
         FIG. 7  shows a cross section through the laser radiation from the laser arrangement shown in  FIG. 5 , on the plane annotated VII; 
         FIG. 8  shows a cross section through the laser radiation from the laser arrangement shown in  FIG. 5 , on the plane annotated VIII; 
         FIG. 9  shows a side view of a second embodiment of an apparatus according to the invention; 
         FIG. 10  shows a plan view of the embodiment shown in  FIG. 9 ; and 
         FIG. 11  shows a perspective view of the embodiment shown in  FIG. 9 . 
     
    
    
     DESCRIPTION OF THE INVENTION 
     In order to improve the clarity, a Cartesian coordinate system is shown in some of the figures. 
     The embodiment, as can be seen from  FIG. 1   a  to  FIG. 4   b  of an apparatus according to the invention, is in the form of a monolithic substrate  1  composed of a material which is at least partially transparent for the laser radiation  4  to be shaped. The substrate  1  has a planar inlet surface  2  (see  FIG. 1   a ,  FIG. 1   b ,  FIG. 2   a  and  FIG. 2   b ) and a planar outlet surface  3  which is parallel thereto (see  FIG. 3   a ,  FIG. 3   b ,  FIG. 4   a  and  FIG. 4   b ) for the laser radiation to be shaped, which are both arranged on an X-Y plane. The inlet surface  2  is more extended in the X direction (see the coordinate systems in  FIG. 2   a  and  FIG. 4   a ), in particular approximately twice as extended, as the outlet surface  3 . In contrast, the outlet surface  3  is more extended in the Y direction, in particular approximately twice as extended as the inlet surface  2 . 
     In  FIG. 1   a , the inlet surface  2  is split into two sections  2   a  and  2   b , which are arranged alongside one another in the X direction, for illustrative purposes. Furthermore, in  FIG. 3   a , the outlet surface  3  is split into two sections  3   a  and  3   b , which are arranged alongside one another in the Y direction, for illustrative purposes. The left-hand or first section  2   a  of the inlet surface  2  in  FIG. 1   a  is directly opposite the lower or first section  3   a  of the outlet surface  3  in  FIG. 3   a , such that a partial beam  4   a  which enters the first section  2   a  in the Z direction, or at right angles to the inlet surface  2 , emerges without being deflected from the first section  3   a  of the outlet surface  3  (in this context, see  FIG. 1   b  to  FIG. 4   b ). The partial beam  4   a  therefore passes through the monolithic substrate  1 , and thus through the apparatus according to the invention, without being deflected. 
     The substrate  1  furthermore comprises a side surface  5  which includes an angle of 45° with the right-hand or second section  2   b  of the inlet surface  2 . A partial beam  4   b  which enters the second section  2   b  of the inlet surface  2  in particular in the Z direction is totally internally reflected through 90° in the negative X direction on the inside of the side surface  5  (in this context, see for example  FIG. 1   b ). 
     The substrate  1  furthermore comprises two side surfaces  6 ,  7  which include an angle of 90° between them and form a prismatic attachment on the side of the substrate  1  opposite the side surface  5  (see for example  FIG. 2   a ). A partial beam  4   b , which moves in the negative X direction, is totally internally reflected through 90° in the Y direction on the inside of the side surface  6  (in this context, see for example  FIG. 1   b ). The partial beam  4   b  which moves in the Y direction is then totally internally reflected through 90° in the X direction on the inside of the side surface  7  (in this context, see for example  FIG. 1   b ). 
     The substrate  1  furthermore comprises a side surface  8  which includes an angle of 45° with the second section  3   b  of the outlet surface  2  (see for example  FIG. 4   a ). The partial beam  4   b , which moves in the X direction, is totally internally reflected through 90° in the Z direction on the inside of the side surface  8  (in this context, see for example  FIG. 1   b ). The partial beam  4   b  then emerges from the second section  3   b  of the outlet surface  3 . Before passing through the substrate  1  in the X direction, the partial beam  4   b  was arranged alongside the partial beam  4   a  and, in  FIG. 1   b , to the right alongside the partial beam  4   a  and, after passing through the substrate  1  in the Y direction, is arranged alongside the partial beam  4   a  and, in  FIG. 1   b , above the partial beam  4   a . The laser radiation  4  is therefore shortened, in particular halved, in the X direction and is increased, in particular doubled, in the Y direction. 
       FIG. 5  and  FIG. 6  show a laser arrangement in which a substrate  1  is installed. The laser arrangement comprises a laser diode bar  9  which has a plurality of emitters which are arranged alongside one another in the X direction. The laser radiation  4  emitted from these emitters is collimated by a collimation means  10 ,  11 , and is rotated by additional beam transformation means  12 . After the second collimation, the laser radiation passes through the substrate  1 . With regard to the laser radiation, a subdivision into partial beams  4   a  and  4   b  is indicated in the drawings, equivalent to  FIG. 1   b  to  FIG. 4   b  in order to illustrate the splitting and superposition of the laser radiation. 
       FIG. 7  shows a cross section through the laser radiation  4  on a plane VII in front of the substrate  1 .  FIG. 8  shows a cross section through the laser radiation  4  on a plane VIII behind the substrate  1 . This shows that the cross section of the laser radiation has been converted from an elongated form with partial beams  4   a ,  4   b  arranged alongside one another, to an approximately square form with partial beams  4   a ,  4   b  arranged one above the other. 
       FIG. 9  to  FIG. 11  show a second embodiment of an apparatus according to the invention. The apparatus shown in these figures comprises three substrates  13 ,  14 ,  15 , which are manufactured from a material which is at least partially transparent for the laser radiation  16  to be shaped. Each of the three substrates  13 ,  14 ,  15  is in the form of a cuboid. The three substrates  13 ,  14 ,  15  are adhesively bonded to one another. 
     The first substrate  13  is a part in the form of a plate which extends essentially in the Z direction, and has a considerably greater extent in the X direction than in the Y direction. The first substrate  13  has an inlet surface  17  and an outlet surface  18 , both of which are arranged on an X-Y plane (see  FIG. 9  and  FIG. 11 ). A partial beam  16   a  of the laser radiation  16  which enters the inlet surface  17  in the Z direction emerges from the outlet surface  18  without being deflected. The partial beam  16   a  therefore passes through the substrate  13 , and thus through the apparatus according to the invention, without being deflected. 
     The second substrate  14  has an inlet surface  19  which is arranged on a plane inclined at an angle of 45° to the X-Y plane. The second substrate  14  has an outlet surface  20 , which is aligned parallel to the inlet surface  19  and is opposite it (see  FIG. 9  and  FIG. 11 ). A partial beam  16   b  of the laser radiation  16  which enters the inlet surface  19  in the Z direction likewise emerges from the outlet surface  20  in the Z direction. However, the emerging partial beam  16   b  is offset somewhat in the Y direction or downwards in  FIG. 9  in comparison to the partial beam  16   b  on entry. The laser radiation  16  is therefore deflected in the Y direction in the second substrate  14 . 
     The third substrate  15  is in the form of a plate with a square outline, which has a considerably smaller extent in the Y direction than in the X direction and in the Z direction. The third substrate  15  is arranged under the first substrate  13  and offset in the Y direction with respect to the first substrate  13 , with respect to  FIG. 9 . An inlet surface  21  and an outlet surface  22  are each aligned at an angle of, for example, 45° to the Z direction (see  FIG. 10 ). 
     A partial beam  16   b  which enters the inlet surface  21  in the Z direction is moved in the interior of the substrate  15  through an angle of for example 45° to the Z direction, and emerges from the outlet surface  22  again in the Z direction. However, the X position of the partial beam  16   b  is shifted in the negative X direction or to the left in  FIG. 10 , as a result of which the partial beam  16   b  now emerges below the partial beam  16   a , or offset in the Y direction with respect thereto, from the outlet surface, with respect to  FIG. 9 . The apparatus which comprises the three substrates  13 ,  14 ,  15  therefore reshapes the laser radiation  16  which is extended in the X direction in a similar manner to that in which the substrate  1  reshapes the laser radiation  4 . 
     According to the invention, it is possible to provide a fourth substrate, which is not shown that is comparable to the second substrate  14 , and which deflects a portion of the laser radiation  16  upwards in  FIG. 9 , or in the negative Y direction. Furthermore, a fifth substrate can then be provided, which is not shown that is comparable to the third substrate  15 , and which deflects that portion of the laser radiation which is deflected upwards in this way, in the X direction or to the right in  FIG. 10 . This allows laser radiation to be broken down into three parts, which are then arranged one above the other in the Y direction.