Abstract:
Optical or optoelectronic module with an optical bench and a laser diode or group of laser diodes located on its top side and first optical and optoelectronic elements positioned sequentially in the direction of the main beam of at least one of the laser diodes, which include at least a focusing lens as well as an optical fiber with two optical end surfaces where the first optical and optoelectronic elements are located in at a first element holder and with the first element holder jointly form a first optical and optoelectronic module, a first assembly holder is located on the top side of the optical bench. The first optical and optoelectronic elements on the element holder are jointly adjustable in the beam path of the light emitted by at least one laser diode and the element holder is located on the assembly holder in such a way that the first optical and optoelectronic elements located on the first element holder are in the beam path of the light emitted by at least one laser diode, and the focusing lens injects light emitted by at least on laser diode into the first optical end surface of the optical fiber.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an optical or optoelectronic module, of the type used, for example, as a source of signals which are transmitted over optical fibers. By means of modules of this type, emitted light from a semiconductor laser is fed into optical fibers, which is required for applications in the areas of telecommunications, for example, pumping lasers, printing and photographic technology, materials processing, medical technology, illumination and display technology, metrology or analytics. 
     Optical modules of this type are disclosed, for example, in publications U.S. Pat. Nos. 4,818,053 and 4,997,279. Each of them shows an optical bench on which a semiconductor laser, an optical fiber and a focusing lens in a bracket is positioned to transmit the emitted radiation from the semiconductor laser into the optical fiber, where the fiber is mounted in a fiber sleeve. Both the lens and the optical fiber are oriented longitudinally along the optical axis of the beam emitted by the laser. 
     The adjustment of the two components is carried out in such a way that first of all the focusing lens is adjusted in three stationary degrees of freedom of translation along the optical axis of the beam emitted by the laser. After the lens has been fixed in position, the optical fiber in turn is adjusted in three degrees of freedom of rotation along the optical axis and fixed in position. The disadvantage here is that the adjustment of the two components is performed sequentially in two separate steps. This requires a high degree of sophistication in the equipment as well as the expenditure of a great deal of time. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to make available an optical or optoelectronic module which can be assembled and adjusted simply and which ensures a precise beam pattern during its entire life and even under adverse conditions. 
     The module under the invention has a first assembly holder as well as a first element holder, where at least one focusing lens and an optical fiber are located on the first element holder in appropriately shaped seats. This array can be set up without any adjustment. The first element holder for its part is located at the first assembly holder, which in turn again is located on an optical bench. The path of the common optical axis of the optical or optoelectronic assembly thus formed is determined by the orientation of the optical axes of the focusing lens, optical fiber and any additional optical and/or optoelectronic components to each other and is thus dependent on the manufacturing tolerances of the element holder. By adjusting the optical assembly in up to three degrees of freedom of translation and up to three degrees of freedom of rotation within a single adjustment step, the optical axes of the assembly and of the beam emitted by the laser diode can be aligned to each other, and the optimal distance of the laser diode to the optical assembly can be set. As a result of this inventive configuration of the optical or optoelectronic array it is possible to locate all the optical and/or optoelectronic components positioned on the element holder jointly in the beam path of the light emitted by the laser diode and thus to obtain/achieve a simple and correct adjustment of the optical or optoelectronic module. 
     The first element holder and the first assembly holder are advantageously formed in such a way that the first element holder is movable in all degrees of freedom with respect to the optical bench. 
     One configuration of the assembly holder, for example, is a U-section open at the top between the flanges of which the element holder is located. The distance between the two flanges is dimensioned such that only a small gap remains on both sides of the element holder between the element holder and the flanges. During the process of adjustment and locking in position, the element holder is held, for example, by a gripping device which is mounted on a positioning system. By means of this positioning system, which can moved advantageously in 6 axes, the element holder and thus the optical module are adjusted for position. Because of its particular configuration, the first assembly holder is moved as well on the assembly surface of the optical bench during the positioning procedure for the first element holder, so that a subsequent adjustment of the assembly holder is not necessary. 
     After adjustment has been completed, the first element holder can be locked in position in the assembly holder with adhesive, and the assembly holder can be held in position on the optical bench. In this process, the first element holder is held in position only laterally against the flanges of the assembly holder, and the assembly holder is only held in place with its underside on the assembly surface of the optical bench. The open space between the first element holder and the upper side of the base plate of the first assembly holder is advantageously not filled with adhesive. 
     Because of the special configuration of the assembly holder and of the element holder, the gaps between the first element holder and the first assembly holder are extremely narrow, and so only a small gap has to be bridged with adhesive. The result is that material shrinkage of the adhesive during curing is negligibly small. As a consequence, the adjustment of the element holder in the assembly holder remains unchanged even after the adhesive has cured. 
     Some examples of optoelectronic modules under the invention are given in the ensuing descriptions. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows an optical or optoelectronic module under the invention; 
     FIG. 2 shows the element holder as shown in FIG. 1; 
     FIG. 3 shows the first optical bench as shown in FIG. 1; 
     FIG. 4 shows an additional optoelectronic module; 
     FIG. 5 shows the first optical bench as shown in FIG. 4; 
     FIG. 6 shows the element holder as shown in FIG. 4; 
     FIG. 7 shows the housing of an optoelectronic module under the invention; 
     FIG. 8 shows the assembly holder under the invention with optical or optoelectronic assembly; and 
     FIGS. 9A-9X show additional assembly holders under the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows an optoelectronic module  1  with a first optical bench  2  (base element). This first optical bench  2  has a U-shaped section, on the two sides of which flanges  40 ,  41  form an opening open to the top. This U-section is closed off at the rear by a wall  7  extending between the two flanges  40 ,  41  and it has a diode bracket  5  on which a semiconductor diode  10  is attached. This semiconductor diode  10  is connected by electrical lead  11  to control and power supply equipment. This laser diode  10  emits light in the direction of the U-section and in this way it defines the beam path of the optoelectronic array. An FAC lens, a Fourier lens  12 , a refracting element  14 , a focusing lens and an optic fiber  18  are positioned in this optoelectronic array immediately after the semiconductor laser  10 . The entire array is adjusted in such a way that the light emitted by the semiconductor laser  10  is injected into the optical fiber  18 . The FAC lens is not shown in the present FIG.  1 . It is bonded to an FAC holder  6 , which is also shaped as a U-section, through whose opening the beam emitted from the semiconductor laser  10  passes. The Fourier lens  12  is located in a recess  13  which in turn is located inside a bridge  46  which runs perpendicular to the U-section between the two flanges  40 ,  41 . In the direction of the beam behind the Fourier lens  12  there is another U-section  3  (assembly holder) running parallel to the U-section of the first optical bench with flanges  44  and  45 , in which an element holder, i.e. a second optical bench  4  is located. This optical bench  4  is also essentially shaped in the form of a U-section, through which the light beam emitted by the semiconductor diode  10  passes. A refracting element  14  is bonded to the face of the element holder  4  facing the laser diode  10 . In the recess  16  or  26  there is either a focusing lens  15  or a fiber sleeve  17 , which encloses the optical fiber  18 . The recesses are formed in such a way that the focusing lens  15  and the optical fiber  18  are optimally adjusted to each other. 
     Under the invention, the element holder  4  is assembled first with the optical elements positioned on it, refracting element  14 , focusing lens  15  and optical fiber  18  with fiber sleeve  17 . After these elements have been adjusted and attached, adhesively bonded for example, the Fourier lens  12  and the FAC lens are adjusted for position in the optical bench  1  and attached. Then the element holder  4  is placed in the U-section  3 , and the U-section  3  is placed in the first U-shaped optical bench  1 . The element holder  4  is held with a gripping device and adjusted. As soon as all the optical elements  14 ,  15  and  18  are optimally positioned in the semiconductor laser beam path, the element holder  4  is bonded in this position into the U-section  3  and the U-section  3  is bonded onto the first optical bench  1 . 
     The optical bench  1  itself can then be bolted into a housing. For this purpose there are bolt holes  8  in the first optical bench  1  through which the bolts can be inserted into a lower housing section and tightened. 
     FIG. 2 shows how the element holder  4  is located within the U-section  3  with its two flanges  44  and  45 . Here, as in the following figures, similar reference numerals as in FIG. 1 are used for similar elements. 
     FIG. 3 shows the first optical bench  1  with the rearward closure  7 , on which the holder for the laser diode can be located and on which in turn the FAC lens can be located. This can be done by bolting, welding, soldering and/or adhesive bonding. In addition, the bridge  46  can be seen, which extends between the two flanges  40  and  41  of the U-shaped optical bench  1 . This bridge  46  has a V-shaped recess  13  to receive the Fourier lens  12  from FIG.  1 . 
     FIG. 4 shows another example of an optoelectronic module  1  with a primary optical bench  2  (base element) and a second optical bench  4  (element holder). In contrast to FIG. 1, the element holder  4  is now located in a U-section  3  with flanges  42  and  43 , which enclose the element holder  4  on both sides, where the U-section  3  for its part is located on a assembly plate  20  (assembly base), which is located between the two flanges  40  and  41  of the U-shaped area of the first optical bench  2 . Here too another bridge  46 , which has a V-shaped recess  13  to position Fourier lens  12 , extends between the two flanges  40  and  41 . The semiconductor diode is now located on a diode holder  5 , which is attached to the first optical bench  2  by means of bolt holes  22 . The first optical bench  2  has a step  21  on its underside, shaped in such a way that the underside of the first optical bench  2  is higher in the area of the laser diode than in the area of the second optical bench  4 . The effect of this step  21  is that a cooling element, for example a Peltier element, can be attached from below to the first optical bench  2  in the area of the laser diode, where, if the height of the step and the height of the Peltier element coincide, the underside of the optical bench runs flush and even with the Peltier element. A space for thermal insulation, which can be filled with a stability-promoting, thermally insulating material, should always be left between the underside of the first optical bench  1  and the bottom of a housing. 
     FIG. 5 shows the first optical bench  2 , where the corresponding bolt holes  23  can now be seen, which match the bolt holes  22  in the diode holder  5 . In the same way, bolt holes  25  can be seen, by means of which the assembly base  20  in the first optical bench can be attached in the first optical bench. 
     FIG. 6 shows the assembly base  20  with its bolt holes  24 , which match the bolt holes  25 . The U-section  3  and the second optical bench  4  are located on this assembly base, where the second optical bench  4  and the U-section  3  are dimensioned in such a way that the second optical bench  4  is partially enclosed on its two long sides, viewed in the direction of the beam, by the flanges  44  and  45  of the U-section  3 . The rest of the construction of the second optical bench  4  is as described previously under FIG.  2 . In FIG. 6 only the focusing lens  15  is shown in its mount  16 , while the refracting element  14  and the fiber sleeve  17  are not shown. 
     FIG. 7 shows a housing of the type that can be used for an optoelectronic component according to the invention. This housing  30  has a housing base  31 , consisting of a base plate, on which there is a housing cover  32 , and four side pieces. The base plate of the housing base  31  has bolt holes  34 , which can be used to bolt the housing  30  securely to a supporting base. In addition, the housing base  31  has lateral openings through which the optical fiber  18  is run on one side and the electrical leads  33  to the laser diode are run on the opposite side. The housing cover  32  is hermetically attached to the housing base, for example by means of welding or soldering. If the openings of the passages are properly sealed and the interior of the housing  30  is filled with inert gas, the result is a completely maintenance-free and very long-lived optoelectronic component. 
     FIG. 8 shows an assembly holder  3 , on which a schematically indicated optical assembly  50  is located. The assembly holder  3  has a U-shape, where the two flanges  44  and  45  have sufficient distance between them that the optical assembly  50  with a predetermined diameter can be positioned between them. 
     FIGS. 9A-9X show different forms of the assembly holder  3  according to the invention. 
     FIGS. 9A and 9B show an assembly holder  3  with two flanges  44  and  45 , extending between which is a V-shaped notch. This V-shaped notch  51  positions an assembly  50  (shown in phantom) with a cylindrical external shape. The V-shaped notch extends from one end of the assembly holder  3  to the other end, where the assembly  50  can be rotated around its cylindrical axis in this V-shaped lengthwise opening. In FIG. 9A an isometric view of the assembly holder is shown. FIG. 9B shows a top view of the assembly holder. 
     FIG. 9C shows the assembly holder  3  in the shape of a U-section with flanges  44  and  45 , where FIG. 9D shows a top view. 
     In FIG. 9E the assembly holder  3  has the shape of a square tube with a lengthwise opening  52  running from one end of the assembly holder  13  to the other end in the axial direction. In the partial illustration in FIG. 9F, a top view of this assembly holder  3  is shown. 
     FIG. 9G shows an assembly holder which also has the same basic shape of a square tube as shown in FIG.  9 E. In contrast to FIG. 9E, the square tube is not completely closed in the horizontal axial direction, but has an opening  53  connecting the lengthwise passage  52  to the outside. A gripping device can be inserted through this opening  53  in order to hold the optical or optoelectronic component in position in the assembly holder during adjustment and attachment to the assembly holder. In each instance only one flange  54  and  55  remains of the top periphery of the assembly holder  3 . FIG. 9H shows a top view of the assembly holder  3 . 
     FIG. 9I shows a U-shaped assembly holder  3 , as depicted in FIG. 9C, where however the two flanges  44  and  45  are connected to each other by means of cross-bridges  56 ,  57  which run perpendicular to the axial direction from one lip of one flange  44  to the lip of flange  45 . Openings remain between the two bridges  56 ,  57  or adjacent to them, through which a gripping device can be inserted. The assembly holder from FIG. 9I of which a top view is shown in FIG. 9J, can also be lifted from a magazine together with the assembly being held by means of the gripping device in the lengthwise opening formed by the flanges  44  and  45  and placed on the assembly surface. 
     FIGS. 9K-9N also show U-shaped assembly holders  3 , as in FIG. 9E in isometric view FIGS. 9K and 9M and viewed from below. FIGS. 9L and 9N, respectively. The underside of the assembly holder is non-planar and has, for example in FIGS. 9M and 9N, channels  60  and  61  running in the axial direction, or in FIGS. 9K and 9L rabbets  58 ,  58   1  running in the axial direction. As is shown in FIG. 9L two or three countersunk holes  59  are provided on the underside of the assembly holder, which for example act as soldering reservoirs or for holding adhesive. 
     FIG. 9O similarly shows a U-shaped section  3  as an assembly holder, where the base of the U-section projects at the sides of the two flanges  44  and  45 . These projections  62 ,  63  have furthermore vertical passages or vertical counterbores  64  on their upper side, which also make attachment of the assembly holder to the surface easier, for example by being filled with adhesive or solder or by spot welding. 
     This is also shown in FIG. 9P as a bottom view of the assembly holder  3 . FIG. 9Q shows an assembly holder as in FIG. 9E, where in this instance however the underside of the assembly holder also projects beyond the two side walls of the square section. These projections  62 ,  63  can also be seen in the top view of FIG.  9 R. 
     As can be seen in FIG. 9S, the inner side of the passage, i.e. the inner side of the flanges  44 ,  45  can be non-planar. In FIG. 9S the flanges  44 ,  45  have extensions  64  at their at each of their axial end surfaces. This can also be seen in the FIG. 9T, the top view of the assembly holder  3 . 
     FIGS. 9U-9X also show U-shaped assembly holders  3 , where however the flanges  44 ,  45  have openings  66 , so that upright flange pieces,  65 ,  65 ′,  65 ′′, and  65 ′′′, are standing only at the four corners of the base plate of the assembly holder  3 . In FIG. 9W two flange pieces  65 ,  65 ′ remain from the flange  44  on one side of the assembly holder  3 , while from the right flange  45  only the center piece which is located opposite the opening  66  remains. In this way better accessibility is created for holding an optical or optoelectronic component in place. Top views of FIGS. 9U and 9W are shown in FIGS. 9V and 9X respectively. 
     The examples from FIGS. 9A to  9 X are intended solely as exemplars, while it must be pointed out that any combination at all of the elements shown there with each other is possible.