Abstract:
The invention relates to a method for producing an optical arrangement ( 10, 300 ), in which an optical component ( 355, 20 ) is optically connected to at least one waveguide ( 90, 320, 330 ) provided on or in a carrier substrate ( 100, 310 ). In order to enable an optical component to be connected to an optical waveguide of a carrier substrate in a particularly simple and thus cost-effective manner, the invention provides for there to be arranged between the optical component ( 20, 355 ) and the waveguide ( 90, 320, 330 ) an adjustment device ( 40, 350 ) with at least one auxiliary waveguide ( 60, 410, 440 ), the waveguide ends ( 50, 70, 400, 420, 430, 450 ) of which are in each case movable and an optical adjustment between the optical component ( 20, 355 ) and the waveguide ( 90, 320, 330 ) of the carrier substrate ( 100, 310 ) is effected by a mechanical adjustment of the movable waveguide ends ( 50, 70, 400, 420, 430, 450 ).

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of the priority date of German application DE 102 48 969.6-51, filed on Oct. 17, 2002, the contents of which are herein incorporated by reference in their entirety. 
     FIELD OF THE INVENTION 
     The present invention is directed to optical components, and more particularly to an optical system and method for coupling an optical component to a waveguide. 
     BACKGROUND OF THE INVENTION 
     In optical telecommunications technology increasingly complex devices are being created which combine a plurality of optical and optoelectrical functions in a common optical arrangement, in particular on a common platform or a common substrate. Examples of such functions or functional elements are optical filters, switches, attenuators, transmitters, amplifiers or receivers. Carriers having combined mechanical, optical, electrical and also thermal functionalities are increasingly being used as the platform. Examples thereof are “electrical optical circuit boards” (EOCB), which are usually used for multimode application, or so-called “planar lightwave circuits” (PLC), that is to say so-called planar optical circuits which are used for multi- or single-mode applications. 
     By way of example, the lightwave circuit in accordance with the published European patent application EP 1 085 354 A1 lies in this field of optical telecommunications technology. Thus, in this previously known method, a photodetector as optical component is placed onto a carrier substrate, to be precise in such a way that the photodetector is optically connected to a waveguide provided in or on the carrier substrate. 
     The invention is based on the object of specifying a method by which an optical component can be connected to an optical waveguide of a carrier substrate in a particularly simple and thus cost-effective manner. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is provided that, in the method according to the invention, an adjustment device with at least one auxiliary waveguide is additionally arranged between the optical component and the waveguide. In this case, the waveguide ends of the auxiliary waveguide are intended to be movable in order that an adjustment of the optical connection between the optical component and the waveguide of the carrier substrate is still possible after the mounting of the optical component. 
     One essential advantage of the method according to the invention is to be seen in the fact that, when mounting the optical component, it is not necessary to make particularly stringent requirements of the adjustment or mounting accuracy; this is because even after the mounting of the optical component on the carrier substrate, for example a “platform”, an adjustment of the optical connection between the component and the waveguide of the carrier substrate is still possible, namely by the auxiliary waveguide of the adjustment device being correspondingly set or adjusted. 
     A further essential advantage of the method according to the invention is to be seen in the fact that it can be carried out in a very simple and thus cost-effective manner. Thus, specifically, the automatic placement machines (“pick and place” machines) that are customary nowadays, as are used in the semiconductor industry, can be used for the mounting of the optical component. These automatic placement machines usually have manufacturing tolerances, in other words mounting tolerances, which are of the order of magnitude of between 5 and 10 μm. As is known, mounting tolerances of this magnitude are totally unacceptable in optical communication applications, primarily in single-mode applications, since, with such large tolerances, an optical coupling or optical connection between different components is possible in poor fashion, i.e. with unnecessary attenuations, or is no longer possible at all. In single-mode applications, mounting tolerances must not exceed a limit value of approximately 1 μm if low-loss optical connections are to be achieved. 
     It is at this point that the invention begins in concrete terms: thus, in the case of the method according to the invention for optically coupling an optical component to a waveguide of a carrier substrate, although an additional component is accepted, which is associated with additional costs and additional production outlay, this additional adjustment device nevertheless makes it possible to use the hitherto customary automatic placement machines. Additional expensive and complicated adjustment devices as would be necessary for mounting optical components on a carrier substrate with micrometer accuracy are not necessary in the case of the method according to the invention. Passive adjustment elements such as, for example, precision micromechanical stops, as are likewise known and customary in the case of mounting accuracies in the micrometer range, are not necessary in the case of the method according to the invention; therefore, the high-precision structuring processes for producing such adjustment elements, for example the precision micromechanical stops mentioned, are likewise obviated. 
     A third essential advantage of the method according to the invention is to be seen in the fact that an optical readjustment between the optical component and the waveguide of the carrier substrate always remains possible in the case of the method according to the invention since the adjustment device enables a readjustment even after the mounting of the optical component. It can be stated in summary, then, that the heart of the invention consists in the fact that the additional provision of an adjustment device with movable waveguide ends enables the use of the automatic placement machines known from semiconductor technology with relatively high mounting inaccuracy (inaccuracy of up to approximately 10 μm). 
     An advantageous development of the method according to the invention provides for this method to be used to mount an optical component on an electrical optical carrier system, for example an electrical optical motherboard, as carrier substrate. The electrical optical carrier system may be for example an electrical optical circuit board or a planar lightwave circuit. As already described above, EOCBs and PLCs have very many functions and thus also functional elements such as e.g. optical filters, switches, attenuators, transmitters, amplifiers or receivers. In order to avoid a complicated adjustment during the production of such “boards” or optical printed circuit boards, the use of the method according to the invention is regarded as advantageous in the case of said boards or printed circuit boards. 
     The adjustment device can be produced particularly simply and thus advantageously if it is formed by an auxiliary substrate in which or on which is provided the at least one auxiliary waveguide with its movable waveguide ends. Substrates with, situated therein or thereon, waveguides with movable waveguide ends are disclosed for example in the article “GaAs-based microelectromechanical waveguide switch”, Olga Blum Spahn, Charles Sullivan, Jeff Burkhart, Chris Tigges, Ernie Garcia, Sandia National Laboratories, Albuquerque, USA, 2000 IEEE/LEOS International Conference on Optical MEMS, Sheraton Kauai, Resort, Kauai, Hi., 21-24 August 2000, TuA5, pages 41 and 42, which is hereby incorporated by reference in its entirety. This is because when the at least one auxiliary waveguide is integrated in or on an auxiliary substrate, it can be ensured that recourse can be had to the customary fabrication techniques from microelectronics or from integrated optics in the production of the adjustment device. 
     The arrangement comprising the optical component, the carrier substrate and the adjustment device can be mounted particularly simply and thus advantageously by a procedure in which the optical component is firstly mounted on the adjustment device and the adjustment device provided with the optical component is subsequently connected to the carrier substrate. 
     In order to enable the optical arrangement produced to be particularly space-saving, it is regarded as advantageous if the adjustment device with the optical component mounted thereon is inserted into a depression at the surface of the carrier substrate. 
     This depression should advantageously be dimensioned in such a way that the waveguides of the adjustment device and those of the carrier substrate lie in one plane. The adjustment device and the carrier substrate may advantageously form a common planar surface. It is possible to have recourse to the known “embedding technique” in the arrangement of the components or the “spatial” integration. 
     The situation in which the adjustment device and the carrier substrate lie in one plane can be achieved particularly simply and thus advantageously by a procedure in which fixing elements are formed at the adjustment device and/or at the carrier substrate, by means of which the adjustment device is suspended in the depression of the carrier substrate. 
     It is regarded as advantageous, moreover, if the fixing elements are simultaneously used for contact connection between the carrier substrate and the adjustment device, since additional electrical contacts are then saved. Indirectly this also simplifies the contact connection between the carrier substrate and the optical component. 
     Another advantageous refinement of the method according to the invention provides for the adjustment device and the carrier substrate to be mounted on a separate carrier. Such a separate arrangement of carrier substrate and adjustment device is recommendable particularly when even further components are intended to be provided on the separate carrier. 
     It will quite generally be unavoidable that joints or cavities will still be present between the optical component, the carrier substrate and the adjustment device after mounting. Therefore, it is regarded as advantageous if these cavities are filled with a composite composition. This composite composition should preferably be configured in such a way that its refractive index is adapted to the refractive index of the adjustment device, of the carrier substrate, of the waveguides in the carrier substrate and/or of the optical component in order to avoid optical reflections. The composite composition may have, in particular, an average refractive index in order to achieve an optimum adaptation. 
     The adjustment device can be formed in a particularly space-saving manner and thus advantageously in that the at least one waveguide is integrated in the adjustment device, to be precise in such a way that its waveguide ends can be deflected and adjusted by means of electrostatic, magnetic, thermal, piezoelectric and/or thermomechanical forces. 
     A particularly low-loss coupling between the optical component and the auxiliary waveguide or the auxiliary waveguide and the waveguide of the carrier substrate can be achieved when an adjustment is possible (two-dimensionally). This can be achieved in concrete terms when the ends of the auxiliary waveguide are in each case movable in the area perpendicular to the longitudinal direction of the auxiliary waveguide and thus perpendicular to the direction of propagation of the light in the auxiliary waveguide—that is to say two-dimensionally. As an alternative or else in addition, the ends of the auxiliary waveguide may be movable along an axis of rotation perpendicular to the longitudinal axis of the auxiliary waveguide—that is to say horizontally, as it were. 
     It is not always the aim to produce a connection between an optical component and the waveguide of the carrier substrate that is as loss-free as possible; thus, sometimes a predetermined amount of attenuation is desirable for the optical connection. In order to achieve such an attenuation, it is regarded as advantageous if the auxiliary waveguide is incorrectly adjusted in a targeted manner in order to achieve the predetermined attenuation between the optical element and the waveguide of the carrier substrate. 
     It is furthermore regarded as advantageous if optical components which have an optical input and an optical output are mounted. Such optical components include for example semiconductor lasers and semiconductor optical amplifiers (SOA). In order to be able to mount these components particularly simply and thus advantageously, at least two adjustable auxiliary waveguides are advantageously provided in the adjustment device, and are in each case optically connected to the optical component and the carrier substrate. It is advantageous, then, if the adjustment device is provided with a corresponding number of auxiliary waveguides for adjustment purposes. 
     An optical arrangement can be formed particularly simply and thus advantageously if a glass or silicon substrate is used as the carrier substrate, since it is possible to have recourse to the known waveguide technology—e.g., based on glass waveguides—in such a case. It goes without saying that other waveguides such as, for example, polymer waveguides or SOI waveguides (SOI: silicon on insulator) may be formed on glass or silicon substrates. 
     In order to achieve the situation in which the least possible optical losses occur between the auxiliary waveguide and the optical component or between the auxiliary waveguide and the waveguide of the carrier substrate, it is regarded as advantageous if the auxiliary waveguide is produced in such a way that its mode field is adapted to that of the waveguide of the carrier substrate and/or to that of the optical component. 
     Moreover, it is regarded as advantageous if holding elements are provided which, after the waveguide ends of the adjustment device have been adjusted, fix the waveguide ends in the adjusted position. The holding elements may be for example mechanical latching elements and/or also elements based exclusively on existing static friction. An essential advantage of such holding elements is that the adjustment device, once the waveguide ends have been adjusted, no longer has to be driven electrically, for example, in order to maintain the adjustment, specifically because the position of the waveguide ends remains fixed. 
     The invention additionally relates to an optical arrangement having an optical component connected to a carrier substrate with at least one optical waveguide. 
     Such an optical arrangement can be gathered for example from the European patent application specified in the introduction. 
     With regard to such an optical arrangement, the invention is based on the object of improving it in such a way that it can be produced particularly simply and thus cost-effectively. 
     With regard to the advantages of the arrangement according to the invention and the advantages of the advantageous refinements of the arrangement according to the invention, reference is made to the corresponding explanations in connection with the method according to the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to elucidate the invention, 
         FIG. 1  shows an exemplary embodiment of an arrangement according to the invention which has been produced by the method according to the invention, to be precise in side view, 
         FIG. 2  shows the exemplary embodiment in accordance with  FIG. 1  in plan view, 
         FIG. 3  shows an exemplary embodiment of an adjustment device for the exemplary embodiment in accordance with  FIGS. 1 and 2  and for the exemplary embodiment in accordance with  FIGS. 4 and 5 , 
         FIG. 4  shows a further exemplary embodiment of an optical arrangement according to the invention which has been produced by the method according to the invention, to be precise in side view, and 
         FIG. 5  shows the exemplary embodiment in accordance with  FIG. 4  in plan view. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows an optical arrangement  10  having an optical component  20 , which has an optical connection  30 . The optical component  20  is mounted on an auxiliary substrate  40 , to be precise in such a way that the connection  30  of the optical component  20  lies opposite a waveguide end  50  of an auxiliary waveguide  60  of the auxiliary substrate  40 . 
     The auxiliary waveguide  60  has a second waveguide end  70 , which lies opposite a waveguide end  80  of a waveguide  90 . This waveguide  90  is integrated in a carrier substrate  100 . 
     The auxiliary substrate  40  and the carrier substrate  100  are mounted on a separate carrier  110  in this case. 
     The optical component  20  may be for example an optical emission element such as a laser or a light-emitting diode or else an optical reception element such as a photodiode. 
     The auxiliary substrate  40  may be for example a glass substrate or a silicon substrate in which or on which optical waveguides are integrated as auxiliary waveguide  60 . The auxiliary waveguide  60  may be for example a glass waveguide or a polymer waveguide or the like. 
       FIG. 2  shows the auxiliary substrate  40  with the optical component  20  in plan view. Besides the optical component  20  and the auxiliary waveguide  60 , the figure reveals a further optical component  20 ′ assigned to a further auxiliary waveguide  60 ′.  FIG. 2  thus indicates that not just one optical component  20  but two or as many other optical components as desired can be fixed on the auxiliary substrate  40 . In a corresponding manner, on the carrier substrate  100  in accordance with  FIG. 1  provision may be made of corresponding waveguide ends  80  and waveguides  90  which provide the corresponding optical connections for the said optical components  20 ,  20 ′ etc. 
     The optical arrangement  10  in accordance with  FIGS. 1 and 2  is preferably produced according to the following method. Firstly, the optical component  20  is mounted on the auxiliary substrate  40 . A standard automatic placement machine can be used for this mounting, since adjustment tolerances of 5 to 10 μm can be accepted. This is because if the connection  30  of the optical component  20  does not lie exactly opposite the first end  50  of the auxiliary waveguide  60 , then the first end  50  of the auxiliary waveguide  60  can be deflected in a subsequent adjustment step. In this case, this deflection is carried out in such a way as to achieve as optimum a coupling as possible between the optical component  20  and the auxiliary waveguide  60  of the auxiliary substrate  40 . 
     Once the optical component  20  has been fixed on the auxiliary substrate, the auxiliary substrate  40  is fixed on the separate carrier  110 . In addition, the carrier substrate  100  is mounted on the separate carrier  110 . A standard automatic placement machine can again be used for the mounting of the auxiliary substrate  40  and of the carrier substrate  100 , since mounting accuracies of the order of magnitude of between 5 and 10 μm are again sufficient. This is because if the waveguide end  80  of the waveguide  90  of the carrier substrate  100  does not lie exactly opposite the second waveguide end  70  of the auxiliary waveguide  60 , then the second waveguide end  70  can be readjusted from its position in a subsequent adjustment step, namely because the second waveguide end  70 — in the same way as the first waveguide end  50 — of the auxiliary waveguide  60  is embodied in movable fashion. The second waveguide end  70  is thus moved and adjusted until an optimum coupling is achieved between the auxiliary waveguide  60  and the waveguide  90  of the carrier substrate  100 . 
     In summary, in the case of the optical arrangement in accordance with  FIGS. 1 and 2 , the optical connection between the optical component  20  and the waveguide  90  of the carrier substrate  100  is adjusted only after the mounting of the elements, namely by the two waveguide ends  50  and  70  of the auxiliary waveguide  60  of the auxiliary substrate  40  being readjusted until an ideal optical coupling to the optical component  20 , on the one hand, and the waveguide  90  of the carrier substrate  100 , on the other hand, is achieved. 
     A deflection of the two waveguide ends  50  and  70  can be achieved in this case if the two waveguide ends  50  and  70  “lie free”. The manner in which it is possible for the two waveguide ends  50  and  70  to “lie free” in this way is shown in detail in  FIG. 3 . 
     Thus,  FIG. 3  reveals the waveguide end  50  of the auxiliary waveguide  60  in cross section. The waveguide end  50  lies free and has no mechanical connection in the lateral or vertical direction to the auxiliary substrate  40 . 
     An electrical contact  200  is applied on the auxiliary waveguide  60  in the region of the waveguide end  50 , the said electrical contact being connected to further electrical contacts  210  on the auxiliary substrate  40 . If an electrical voltage is then applied between the connection  200  and one of the two connections  210 , then a lateral deflection of the waveguide end  50  occurs on account of the electrostatic forces which form. This is indicated by a double arrow  220  in  FIG. 3 . The deflected position of the waveguide end  50  is identified by the reference symbol  230 . 
     Thus, an adjustment of the waveguide end  50  relative to the connection  30  of the optical component  20  can be achieved by applying a corresponding voltage to the connections  200  and  210 . 
     The second waveguide end  70  of the auxiliary waveguide  60  can also be deflected in a corresponding manner in order to achieve the optical coupling to the waveguide  90  of the carrier substrate  100 . 
     Moreover, further electrical connections may be provided above and/or below the two waveguide ends  50  and  70  of the auxiliary waveguide  60 , which connections enable the waveguide ends to be adjusted vertically. This is indicated in  FIG. 3  by the reference symbol  240 , identifying a vertically deflected position of the waveguide end  50 . 
     The adjustment device in accordance with  FIG. 3  may be formed for example in a silicon or glass substrate. 
     Moreover, the optical component  20  does not have to be fixed on the auxiliary substrate  40 ; instead, the optical component  20 , the auxiliary substrate  40  and the carrier substrate may also be arranged alongside one another on the separate carrier  110 . 
       FIG. 4  shows a further exemplary embodiment of an optical arrangement according to the invention. This optical arrangement bears the reference symbol  300  in  FIG. 4 . The optical arrangement  300  has a carrier substrate  310  with a first waveguide  320  and a second waveguide  330 . A depression  340  is provided in the carrier substrate  310 , an adjustment device formed by an auxiliary substrate  350  being inserted into the said depression. The connection between the auxiliary substrate  350  and the carrier substrate  310  is ensured by adjustment bumps  360  as fixing elements. 
     An optical component  355  is mounted at the auxiliary substrate  350 . This optical component  355  is a laser amplifier with two connections  370  and  380 . 
     The first connection  370  is optically connected to a first waveguide end  400  of a first auxiliary waveguide  410 . The first auxiliary waveguide  410  has a second waveguide end  420 , which is optically connected to the first waveguide  320  of the carrier substrate  310 . 
     The second connection  380  of the optical component  355  lies opposite a first waveguide end  430  of a second auxiliary waveguide  440 . The second waveguide end  450  of the second auxiliary waveguide  440  is in turn arranged in such a way that it is optically connected to the second waveguide  330  of the carrier substrate  310 . 
       FIG. 5  shows the auxiliary substrate  350  in accordance with  FIG. 4  in plan view. The figure reveals that, besides the first auxiliary waveguide  410  and the second auxiliary waveguide  440 , there are even further auxiliary waveguides, to be precise a third auxiliary waveguide  460  and a fourth auxiliary waveguide  470 . The third auxiliary waveguide  460  and the fourth auxiliary waveguide  470  serve for the connection of a further optical component  480 , which, by way of example, may likewise be a laser amplifier. 
     Moreover,  FIG. 5  reveals the fixing bumps  360  for fixing the auxiliary substrate  350  on the carrier substrate  310 . 
     The carrier substrate  310  may be for example an electrical optical carrier system, for example an electrical optical motherboard. The carrier substrate may be, in concrete terms, for example an “electrical optical circuit board” (EOCB) or a “planar lightwave circuit” (PLC). The optical arrangement in accordance with  FIGS. 4 and 5  is advantageously produced as follows: 
     Firstly, the optical component  355  is mounted on the auxiliary substrate  350 . The adjustment accuracy is not very important in this adjustment, and so tolerances of 5 to 10 μm are acceptable. Consequently, the optical component  355 — in the same way as the further optical component  480 — can be mounted on the auxiliary substrate  350  using the automatic placement machines that are customary in semiconductor technology. 
     After the mounting of the optical component  355  or of the further optical component  480  on the auxiliary substrate  350 , the premounted auxiliary substrate  350  is inserted into the depression  340  of the carrier substrate  310 . This mounting may also exhibit certain tolerances, so that once again it is possible to use customary automatic placement machines from the semiconductor industry. 
     As soon as the auxiliary substrate  350  has been mounted on the carrier substrate  310 , the waveguide ends  400  and  420  of the first auxiliary waveguide  410  and also the two waveguide ends  430  and  450  of the second auxiliary waveguide  440  are aligned in such a way as to achieve an optimum optical connection between the optical component  355  and the two waveguides  320  and  330  of the carrier substrate  310 . 
     As already mentioned above, the carrier substrate  310  in accordance with  FIGS. 4 and 5  or the carrier substrate  100  in accordance with  FIGS. 1 and 2  may be a so-called PLC (planar lightwave circuit) or an EOCB (electrical optical circuit board). EOCBs are preferably to be used for multimode applications, whereas PLCs can be used for multi- or single-mode applications. 
     In the case of PLCs, one or more functional layers (e.g. made of glass, silicon, polymers, metals or any desired combination of these materials) may be deposited on the carrier substrate material (e.g., glass or silicon) and be structured by various technologies in order to form the waveguides  320 ,  330  in the carrier substrate  310 . 
     However, many functions (e.g., filters) may be realized directly by suitable structuring of the EOCB or PLC platform  310  or  100 . Other functions or functional units are then adjusted—as explained in connection with FIGS.  1  to  5 —by mounting the corresponding elements on the EOCB or PLC platform  310  or  100  in the manner described. 
     Although the invention has been illustrated and described with respect to one or more implementations, alterations and/or modifications may be made to the illustrated examples without departing from the spirit and scope of the appended claims. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application. Furthermore, to the extent that the terms “including”, “includes”, “having”, “has”, “with”, or variants thereof are used in either the detailed description and the claims, such terms are intended to be inclusive in a manner similar to the term “comprising”. 
     LIST OF REFERENCE SYMBOLS 
     
         
           10  Optical arrangement 
           20  Optical component 
           30  Connection of the optical component 
           40  Auxiliary substrate 
           50  First waveguide end 
           60  Auxiliary waveguide 
           70  Second waveguide end 
           80  Waveguide end 
           90  Waveguide 
           100  Carrier substrate 
           110  Separate carrier 
           200  Electrical contact 
           210  Electrical contact 
           220  Arrow (direction of movement) 
           230  Waveguide in laterally deflected position 
           240  Waveguide in vertically deflected position 
           300  Optical arrangement 
           310  Carrier substrate 
           320  First waveguide 
           330  Second waveguide 
           340  Depression 
           350  Auxiliary substrate 
           355  Optical component 
           360  Fixing bumps 
           370  First connection 
           380  Second connection 
           400  First waveguide end 
           410  First auxiliary waveguide 
           420  Second waveguide end 
           430  First waveguide end 
           440  Second auxiliary waveguide 
           450  Second waveguide end 
           460  Third auxiliary waveguide 
           470  Fourth auxiliary waveguide 
           480  Further optical component