Abstract:
The invention relates to a laser amplifier system consisting of a solid body, which comprises a laser-active medium, of a pumping radiation source for generating a pumping radiation field, which repeatedly permeates the solid body, and of a focusing system. Said focusing system generates a number of different branches of the pumping radiation field that enter the solid body and converts at least one branch emerging from the solid body into one of the branches which enter the solid body and which are different from the emerging branch. The aim of the invention is to improve a laser amplifier system of the aforementioned type in order to be able to generate the highest possible pumping power density in the solid body while requiring the smallest possible amount of complexity. To this end, the focusing system comprises at least one deviating unit which converts, by deviating the radiation field with regard to a single plane of symmetry, at least two first partial branches formed from at least two different branches of the pumping radiation field emerging from the solid into at least two corresponding second partial branches which locally extend in a manner that is separate from the first partial branches and of which at least two branches entering the solid body are formed.

Description:
[0001]    The present disclosure relates to the subject matter disclosed in PCT application No. PCT/EP01/01129 of Feb. 2, 2001, which is incorporated herein by reference in its entirety and for all purposes. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The invention relates to a laser amplifier system comprising a solid body having a laser-active medium, a pump radiation source for producing a pump radiation field which passes multiply through the solid body, and a focusing system which produces a plurality of different branches of the pump radiation field that enter the solid body, and in this case converts at least one branch that emerges from the solid body into one of the branches that enter the solid body and are different from the emerging branch.  
           [0003]    Such a laser amplifier system is known from the prior art, for example from EP 0 632 551.  
           [0004]    In these laser amplifier systems, the branch that emerges from the solid body is merely deviated and refocused onto the solid body.  
           [0005]    The disadvantage of such a focusing system is that, with it, the cross section of the pump radiation field to be focused is always increased or significant losses arise because a part of the pump radiation field is not refocused back onto the solid body.  
           [0006]    Overall, achieving the highest possible pump power radiation density in the solid body is problematic, especially under the premise that the greatest possible number of passes of the pump radiation field is striven for, since the absorption by the laser-active medium in the body during a single pass of the pump power is small.  
           [0007]    It is therefore an object of the invention to improve a laser amplifier system of the generic type in such a way that the highest possible pump power density in the solid body can be achieved with the least possible outlay.  
         SUMMARY OF THE INVENTION  
         [0008]    This object is achieved according to the invention, in the case of a laser amplifier system of the type described in the introduction, by the fact that the focusing system comprises at least one deviating unit which, by radiation field deviation relative to a single symmetry plane, converts at least two first sub-branches, formed from at least two different branches of the pump radiation field that emerge from the solid body, into at least two corresponding second sub-branches with trajectories locally separate from the first sub-branches, from which at least two branches that enter the solid body are obtained.  
           [0009]    The advantage of the solution according to the invention is that it provides a straightforward way, with a deviating unit which deviates relative to a single symmetry plane, of in turn producing two different branches that enter the solid body from at least two different emerging branches of the pump radiation field.  
           [0010]    As an alternative or supplement to this, a further laser amplifier system according to the invention, which likewise achieves the object stated in the introduction, provides for the focusing system to comprise two deviating units, for each of the deviating units to convert at least one first sub-branch, formed from an emerging branch, into a second sub-branch with a trajectory locally different from the latter, and for each of the deviating units to produce a second sub-branch, from which one of the incident branches is obtained which, for its part, in turn leads to an emerging branch from which a first sub-branch that strikes the other deviating unit is obtained.  
           [0011]    The advantage of this solution according to the invention that is it provides a straightforward way of producing a large number of different focused branches that enter the solid body.  
           [0012]    In an alternative or supplementary embodiment of the solution according to the invention, provision is made for the focusing system to comprise a first deviating unit and a second deviating unit, and for the two deviating units, respectively by radiation field deviation relative to a single symmetry plane, to convert overall at least three first sub-branches, formed from at least three different emerging branches of the pump radiation field, into at least three corresponding second sub-branches with trajectories locally separate from the first sub-branches, from which at least three incident branches are obtained.  
           [0013]    The advantage of this solution is likewise that it provides an extremely straightforward way of producing as many incident branches as possible.  
           [0014]    As an alternative and/or supplement to the solutions according to the invention described above, provision is made in a particularly preferred embodiment for the focusing system to have at least one deviating unit, and for the deviating unit to form, from one of the first sub-branches, a second sub-branch which is offset in relation to the mid-axis of the focusing system by an angular spacing such that at least one further first sub-branch lies in the angle range between this first sub-branch and the second sub-branch formed therefrom.  
           [0015]    This solution also has the advantage that it provides a particularly straightforward way of producing as large as possible a number of incident branches that are focused onto the solid body.  
           [0016]    As an alternative and/or supplement to the solutions described above, provision is made in a further preferred embodiment for the focusing system to have a first deviating unit, which deviates the pump radiation field relative to a first deviating symmetry plane, and to have a second deviating unit, which deviates the pump radiation field relative to a second deviating symmetry plane, and for the symmetry planes to meet at an angle which corresponds to 180° or 360° divided by the sum of the incident and emerging branches arising during a pass of the pump radiation field through the focusing system and the solid body.  
           [0017]    The term “pass of the pump radiation field through the focusing optics” means that the pump radiation field propagates, with one propagation direction, through the focusing optics and strikes the respective optical elements once.  
           [0018]    In terms of the orientation of the symmetry plane of the deviating units, no detailed indications have been given so far. For instance, in order to obtain beam guiding conditions that are as simple as possible, it is advantageous for the symmetry planes to run parallel to the mid-axis.  
           [0019]    It is particularly favorable, for the arrangement of the individual sub-branches and branches, for the symmetry planes to run through the mid-axis.  
           [0020]    In terms of the arrangement of the first sub-branches in the pump radiation field, no detailed indications have been given so far. It is particularly favorable in this case for the first sub-branches to have separate trajectories from one another in the pump radiation field, that is to say they at most touch, and preferably have a small spacing from one another.  
           [0021]    It is particularly favorable in this case for the first sub-branches to be arranged relative to one another at angular spacings around a mid-axis of the focusing system.  
           [0022]    It is also advantageous, in terms of the second sub-branches, for them to have separate trajectories from one another.  
           [0023]    It is particularly favorable in this case for the second sub-branches to have separate trajectories from the first sub-branches as well.  
           [0024]    A particularly favorable solution provides for the second sub-branches to be arranged relative to one another, and relative to the first sub-branches, at angular spacings around the mid-axis of the focusing system.  
           [0025]    In this case, the angular spacings may be small, although it is advantageous for there to be at least a small angular spacing so that the sub-branches can respectively be arranged separately from one another.  
           [0026]    In particular, in all embodiments of the solution according to the invention in which at least three first sub-branches and at least three second sub-branches arise, provision is made for the at least three first sub-branches and the at least three second sub-branches to arise during a pass of the pump radiation field through the focusing system and the solid body, the term “pass through the focusing system” being intended to mean that the pump radiation field propagates in one direction through the focusing system and in this case forms the various branches and sub-branches.  
           [0027]    A particularly advantageous arrangement of the first and second sub-branches provides for the first and second sub-branches arising during a pass of the pump radiation field through the branch focusing system to be arranged without overlap in the space around the mid-axis of the focusing system.  
           [0028]    It is particularly advantageous, especially in terms of the pump radiation branch that is furthermore required, for the first and second sub-branches as well as the pump radiation branch of a pass to be arranged without overlap in the space around the mid-axis of the focusing system.  
           [0029]    A particularly favorable type of arrangement of the first and second sub-branches provides for the first and second sub-branches to be respectively arranged in space segments around the mid-axis of the focusing system, and for them to extend inside the space segments transversely with respect to their propagation direction, but not to reach beyond the space segments allocated to them.  
           [0030]    A particularly advantageous distribution can be obtained when each of the space segments stretches over approximately the same angle range around the mid-axis.  
           [0031]    A particularly uniform distribution of the focused branches that enter the solid body can be obtained when the space segments of the first and second sub-branches, as well as the space segment of the pump radiation branch, substantially enclose the mid-axis.  
           [0032]    In terms of the specifics of the design of the focusing system, no detailed indications have been given in connection with the explanation of the individual exemplary embodiments so far. For instance, an advantageous solution provides for the focusing system to convert a branch that emerges from the solid body into an intermediate-collimated branch, and for it to convert the intermediate-collimated branch in turn into a branch that again enters the solid body and is focused onto it. This solution has the great advantage that precise imaging conditions can thereby be obtained and, in particular, the beam cross section does not experience any broadening in the course of the refocusing.  
           [0033]    In principle, the deviating units may be arranged in such a way that they act on each of the branches. It is particularly favorable for the intermediate-collimated branches to form the first and second sub-branches, which enter or depart from the deviating units, so that the deviation takes place in the vicinity of the collimated branches.  
           [0034]    In terms of the course of the first and second sub-branches, no detailed indications have been given in connection with the explanation of the individual exemplary embodiments so far.  
           [0035]    For instance, particularly advantageous optical imaging conditions can be achieved when the first and second sub-branches run parallel to one another.  
           [0036]    It is even more favorable for the first and second sub-branches to run parallel to the mid-axis, since then the collimating and focusing elements can also be orientated in the same way relative to the mid-axis.  
           [0037]    A solution that is particularly advantageous in terms of the geometrical proportions in this case provides for the first and second sub-branches to be arranged at approximately the same radial spacing around the mid-axis. In this case, the focusing and collimating elements can be arranged particularly favorably relative to the mid-axis, in order to achieve imaging conditions that are as standardized as possible.  
           [0038]    The indications above in terms of the first and second sub-branches advantageously also apply to the pump radiation branch, so that the latter is also advantageously oriented parallel to the first and second sub-branches and, even more advantageously, also parallel to the mid-axis.  
           [0039]    It is particularly advantageous if the pump radiation branch already runs at approximately the same radial spacing from the mid-axis as the first and second sub-branches as well.  
           [0040]    In terms of the structure of the focusing system, a very wide variety of solutions are conceivable. For example, the focusing and deviation may be carried out with the same elements. It is particularly favorable, however, for the focusing system to have collimating and focusing elements, which convert the incident branches into intermediate-collimated branches and the intermediate-collimated branches into incident branches, respectively.  
           [0041]    Such collimating and focusing elements may be provided as individual elements for each deviation of an emerging branch into an intermediate-collimated branch, or of each intermediate-collimated branch into an incident focused branch. It is particularly favorable for all the collimating and focusing elements to be designed identically.  
           [0042]    In terms of the design of the collimating elements, no detailed indications have been given so far. For instance, it would be conceivable to use lenses as the collimating and focusing elements.  
           [0043]    A particularly favorable structure can be achieved when the collimating and focusing elements are formed by concave mirrors.  
           [0044]    Such concave mirrors may, for example, be mirrors that are parabolic in cross section or are shaped as a circle arc in cross section.  
           [0045]    For instance, the mirrors may in principle be designed in such a way that they produce a line focus. It is even better for the concave mirrors to be designed in such a way that they produce a substantially point-like focus.  
           [0046]    In the simplest case, the collimating and focusing elements are designed in such a way that they are segments of a rotationally symmetrical mirror, the mirror preferably being arranged rotationally symmetrically with respect to the mid-axis of the focusing system.  
           [0047]    It is even more favorable, however, for the collimating and focusing elements to be segments of a continuous rotationally symmetric concave mirror.  
           [0048]    In terms of the arrangement of the deviating units relative to the collimating and focusing elements, provision is preferably made for the deviating units to be arranged in such a way relative to the collimating and focusing elements that they deviate the intermediate-collimated branches from a collimating element onto a focusing element.  
           [0049]    In terms of the branch of the pump radiation field arising after a pass through the focusing system, no detailed indications have been given so far. For instance, it would be conceivable simply to leave unused the last branch that emerges from the solid body.  
           [0050]    It is particularly advantageous, however, for a collimated branch to be formed after a pass of the pump radiation field through the focusing system, since such a collimated branch can still be used further with the power that is still available.  
           [0051]    A favorable solution provides for the collimated first sub-branch formed after a pass through the focusing system to be converted into a second sub-branch that is substantially congruent with the first sub-branch.  
           [0052]    Such conversion of a first sub-branch into a substantially congruent second sub-branch may optionally be carried out by obtaining the second sub-branch that is substantially congruent with the first sub-branch by back-reflection at a plane reflection surface.  
           [0053]    As an alternative to this, it is possible according to the invention for the second sub-branch that is substantially congruent with the first sub-branch to occur by reflection at a symmetry-preserving deflecting reflection system, the possibility being available to make the second sub-branch return laterally inverted with respect to the first sub-branch.  
           [0054]    A particularly advantageous solution of the laser amplifier system according to the invention provides for the focusing system to have at most two deviating units allocated to the solid body, which convert a first sub-branch, formed from a branch that emerges from the solid body, into a second sub-branch which forms one of the branches that enter this solid body, so that the same solid body is always multiply illuminated by the two deviating units.  
           [0055]    The laser amplifier system according to the invention is not, however, restricted to solutions with a single solid body.  
           [0056]    An advantageous solution provides for it to comprise at least two solid bodies, and for at least one third deviating unit to be provided which deviates a branch of the pump radiation field transversely with respect to a further symmetry plane stretching between the solid bodies.  
           [0057]    The advantage of this solution is that either two independent lasers can thereby be pumped with the same pump radiation field, or the possibility is provided of arranging the two solid bodies in such a way that they are used to amplify one laser radiation field passing through them, so that the pump radiation can be optimally utilized.  
           [0058]    In terms of the design of the deviating units used according to the invention, no detailed indications have been given so far. For instance, an advantageous exemplary embodiment provides for the deviating unit to comprise two reflection faces running at an angle to one another. The reflection faces may in this case run at a spacing from one another.  
           [0059]    Provision is preferably made, however, for the reflection faces to abut one another along a line.  
           [0060]    The reflection faces may in principle be arranged on different supports. A particularly advantageous exemplary embodiment provides for the reflection faces to be arranged on a reflector unit.  
           [0061]    Preferably, such a reflector unit constitutes a prism.  
           [0062]    In terms of the arrangement of the first and second deviating units, no detailed indications have been given so far. For instance, an advantageous solution provides for the first and second deviating units to form a recess through which the branches that enter or emerge from the solid body pass, so that all the incident and emerging branches run in the direction of the mid-axis of the focusing system and strike the solid body that preferably runs symmetrically with respect to the mid-axis.  
           [0063]    In order to be able to route the pump radiation branch furthermore in a straightforward way, provision is preferably made for the deviating units to form a recess through which a pump radiation branch enters the focusing system.  
           [0064]    Further features and advantages of the invention are the subject matter of the following description and the graphical representation of several exemplary embodiments. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0065]    [0065]FIG. 1 shows a perspective view of a first exemplary embodiment of a laser amplifier system according to the invention from the lower front;  
         [0066]    [0066]FIG. 2 shows a perspective view of the laser amplifier system according to the invention from the upper front;  
         [0067]    [0067]FIG. 3 shows a perspective view of a laser amplifier system according to the invention from behind;  
         [0068]    [0068]FIG. 4 shows a similar sub-view to FIG. 2 in order to demonstrate the first focused incident branch, the first defocused emerging branch and the first collimated branch;  
         [0069]    [0069]FIG. 5 shows a similar view to FIG. 2 in order to demonstrate the second focused incident branch and the second defocused emerging branch as well as the second collimated branch;  
         [0070]    [0070]FIG. 6 shows a similar view to FIG. 2 in order to demonstrate the third focused branch, the third focused incident branch, the third defocused emerging branch and the third collimated branch;  
         [0071]    [0071]FIG. 7 shows a similar view to FIG. 2 in order to demonstrate the fourth focused incident branch, the fourth defocused emerging branch and the fourth collimated branch;  
         [0072]    [0072]FIG. 8 shows a perspective view from behind based on the view in FIG. 3, but without deviating units in order to demonstrate the course of the collimated pump radiation branch, the first focused incident branch, the first defocused emerging branch and the first collimated branch;  
         [0073]    [0073]FIG. 9 shows a similar view to FIG. 8 in order to demonstrate the course of the second focused incident branch, the second defocused emerging branch and the second collimated branch;  
         [0074]    [0074]FIG. 10 shows a similar view to FIG. 8 in order to demonstrate the third focused incident branch, the third defocused emerging branch and the third collimated branch;  
         [0075]    [0075]FIG. 11 shows a similar view to FIG. 8 in order to demonstrate the course of the fourth focused incident branch, the fourth defocused emerging branch and the fourth collimated branch;  
         [0076]    [0076]FIG. 12 shows a schematic plan view of the deviating units of the first exemplary embodiment together with a representation of space segments in which the collimated branches run;  
         [0077]    [0077]FIG. 13 shows a similar representation to FIG. 12 in the case of a second exemplary embodiment;  
         [0078]    [0078]FIG. 14 shows a similar representation to FIG. 12 in the case of a third exemplary embodiment;  
         [0079]    [0079]FIG. 15 shows a similar representation to FIG. 12 in the case of a fourth exemplary embodiment;  
         [0080]    [0080]FIG. 16 shows a similar representation to FIG. 12 in the case of a fifth exemplary embodiment;  
         [0081]    [0081]FIG. 17 shows a similar representation to FIG. 12 in the case of a sixth exemplary embodiment; and  
         [0082]    [0082]FIG. 18 a similar representation to FIG. 12 in the case of a seventh exemplary embodiment. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0083]    A first exemplary embodiment of a laser amplifier system according to the invention, represented in FIGS.  1  to  12 , comprises a disk-shaped solid body  10  having a laser-active medium, which has a frontal flat side  12  and a rear flat side  14  that may be either plane or curved, and which rests via its rear flat side  14  on a reflector  16 . Preferably, the reflector  16  is in this case applied to the rear flat side  14  as a layer.  
         [0084]    Furthermore, the solid body  10  is preferably cooled via the reflector  16 , and hence the rear flat side  14 , such cooling being implementable, in particular, by using a cold finger on which the reflector  16  rests with thermal contact.  
         [0085]    A pump radiation field, denoted as a whole by  20 , which is defined by a focusing system, denoted as a whole by  30 , and the reflector  16 , is injected into the solid body  10  via the frontal flat side  12 , and in this case passes multiply through the solid body  10 , so that the laser-active medium in the solid body  10  can be excited by the pump radiation field  20  upon each pass through the solid body  10 .  
         [0086]    The laser-active medium in the solid body  10  produces a laser radiation field  40  which, for example, is likewise reflected by the reflector  16 , emerges through the frontal flat side  12  of the solid body  10  and propagates in the direction of a mid-axis  42  of the laser amplifier system, for example with separate optics being provided for the laser radiation field  40 , for example a resonator or optics that multiply reflect the laser radiation field  40 , so that the laser radiation field  40  likewise passes multiply through the solid body  10 .  
         [0087]    Such a laser amplifier system is, for example, described from basic principles in EP 0 632 551, to which comprehensive reference is made in terms of the operating procedure of the laser amplifier system, the arrangement of the solid body  10  and the reflector  16 , as well as the cooling thereof.  
         [0088]    A pump radiation source  22  provided in order to generate the pump radiation field  20  is, for example, a laser, preferably a semiconductor laser, whose laser radiation  24  is routed via a beam guiding system, for example an imaging system or a fiber optic system, to the laser amplifier system according to the invention with the formation of a collimated pump radiation branch  26 , which passes through a first space segment  32   1  of the focusing system  30  and strikes a focusing element, for example a first segment  50   1  of a parabolic mirror, denoted as a whole by  50 , which is part of the focusing system  30 .  
         [0089]    By the segment  50   1  of the parabolic mirror  50 , a third incident branch  52   1  is formed from the pump radiation branch  26  and is focused onto the solid body  10 , enters it through the frontal flat side  12 , passes through the solid body  10  and is reflected back by the reflector  16 , so as to obtain a first emerging branch  54   1  which propagates as a defocused branch in the direction of the parabolic mirror  50  and strikes a collimating element, for example a fifth segment  50   5  of the parabolic mirror  50 . From the first emerging branch  54   1 , this fifth segment  50   5  forms a first collimated branch  56   1  of the pump radiation field  20  which, starting from the fifth segment  50   5  of the parabolic mirror  50  and in the form of a first sub-branch  56   1a  propagating parallel to the mid-axis  42  in a fifth space segment  32   5  (FIG. 12), propagates starting from the parabolic mirror  50  in the direction of a first deviating unit  60  which is formed, for example, by a prism  62  that comprises two reflector faces  64  and  66 , which meet at an angle of 90° and are arranged symmetrically with respect to a symmetry plane  68  that runs parallel to the mid-axis  42  and through it.  
         [0090]    The first sub-branch  56   1a  of the collimated branch  56   1 , which runs in the space segment  32   5 , in this case strikes the reflector face  64  which forms by reflection the deviated branch  56   1b  of the collimated branch  56   1 , which for its part, by reflection at the reflector face  66 , is in turn reflected parallel to the sub-branch  56   1a , but at a spacing therefrom, in the direction of the parabolic mirror  50  and propagates in the direction of the parabolic mirror  50  in the form of a second sub-branch  56   1c  in an eighth space segment  32   8  and finally strikes the focusing element, for example the eighth segment  50   8  of the parabolic mirror  50 , so that overall the sub-branches  56   1a  and  56   1c  run at an angular spacing from one another in relation to the mid-axis  42  in the collimated branch  56   1 , and deviation of the collimated branch  56   1  from the fifth space segment  32   5  to the eighth space segment  32   8  therefore takes place overall.  
         [0091]    From the branch  56   1c  of the collimated branch  56   1 , the eighth segment  50   8  of the mirror  50  forms a second incident and focused branch  52   2  which, for its part, in turn strikes the solid body  10 , passes through it and is reflected by the reflector  16 , so that a second emerging defocused branch  54   2  is obtained, which strikes a further collimating element, for example the segment  50   4  of the parabolic mirror  50 , which forms, from the emerging branch  54   2 , a second collimated branch  56   2  that propagates with its sub-branch  56   2a  in a fourth space segment  32   4  (FIG. 12) in the direction of a second deviating unit  70  (represented in particular in FIG. 3) which is likewise formed as a prism  72  and has reflector faces  74  and  76  which meet at an angle of 90° and are arranged symmetrically with respect to a symmetry plane  78  that runs parallel to the mid-axis  42  and through it. The symmetry plane  78  however, as represented in FIG. 12, is arranged in relation to the symmetry plane  68  at an angle α which is equal to 22.5°.  
         [0092]    The deviating unit  70  therefore causes deviation of the second collimated branch  56   2  via the deviated sub-branch  56   2b  symmetrically with respect to the symmetry plane  78 , so that the reflection faces  74  and  76  produce a second sub-branch  56   2c  which runs parallel to the sub-branch  56   2a  in a second space segment  32   2 , strikes a focusing element in the form of the second segment  50   2  of the parabolic mirror and is therefore likewise arranged offset in relation to the sub-branch  56   2a  by an angular spacing with respect to the mid-axis  42 .  
         [0093]    The second segment  50   2  forms, from the sub-branch  56   2c  of the collimated branch  56   2 , the third incident branch  52   3  that is focused onto the solid body  10 , which passes through the solid body  10  and is reflected at the reflector  16 , so that the third emerging branch  54   3  is obtained which strikes the sixth segment  50   6 , which constitutes a collimating element, of the parabolic mirror denoted as a whole by  50 , and this forms the third collimated branch  56   3  which, for its part, in turn propagates with the first sub-branch  56   3a  in a sixth space segment  32   6  (FIG. 12) in turn in the direction of the deviating unit  60 , so that by using the reflection faces  64  and  66 , via the formation of the deviated sub-branch  56   3b , the second sub-branch  56   3c  is obtained which propagates in a seventh space segment  32   7  (FIG. 12) in the direction of the parabolic mirror  50  and strikes the segment  50   7  thereof that constitutes a focusing element, with the sub-branches  56   3a  and  56   3c  in turn propagating parallel to one another and parallel to the mid-axis  42 .  
         [0094]    The third collimated branch  56   3  in this case runs, as represented in FIGS. 1 and 2, in such a way that all the sub-branches  56   3a ,  56   3b  and  56   3c  lie in an angle range that covers the space segments  32   7  and  32   7  between the sub-branches  56   1a  and  56   1c  of the first collimated branch, so that the first collimated branch  56   1  and the third collimated branch  56   3 , although they are both deviated by the deviating unit  60 , do not overlap but both experience a deviation symmetrically with respect to the symmetry plane  68 .  
         [0095]    By using the segment  50   7  of the parabolic mirror  50 , the formation of a fourth incident branch  52   4  takes place, which strikes the solid body  10  and is reflected by the reflector  16 , so that the fourth emerging branch  54   4  is obtained which strikes a third segment  50   3  that constitutes a collimating element of the parabolic mirror  50 , which produces the fourth collimated branch  56   4  in a third space segment  32   3  (FIG. 12). This concludes a pass of the pump radiation field  20  through the refocusing optics  30  and the solid body  10 .  
         [0096]    Owing to fact that the fourth collimated branch  56   4  runs symmetrically with respect to the symmetry plane  78 , it can be reflected back on itself in relation to the overall collimated branch, although since half of the fourth collimated branch  56   4  with its first sub-branch  56   1a  strikes the reflection face  74  and half of it strikes the reflection face  76 , the returning sub-branch  56   4c  runs laterally inverted in relation to the first sub-branch  56   4a  with respect to the symmetry plane  78 .  
         [0097]    Furthermore, the production of the returning second sub-branch  56   4c  presupposes that the reflection faces  74  and  76  abut one another, specifically along a contact line running in the symmetry plane  78 .  
         [0098]    This returning sub-branch  56   4c  provides the opportunity to make the pump radiation field  20  pass again through the refocusing optics  30  and through the solid body  10  via a further pass, with the path of the pump radiation field being inverted and with the four emerging defocused branches  54   1  to  54   4  becoming incident focused branches and the incident focused branches  52   1  to  52   4  becoming emerging defocused branches.  
         [0099]    This provides the opportunity, in the first exemplary embodiment, to make the pump radiation field  20  pass overall 16 times through the solid body  10 , namely since the four incident branches  52   1  to  52   4  of the first pass and the four emerging branches  54   1  to  54   4  of the first branch give rise to eight transmissions and the second pass likewise gives rise to eight transmissions.  
         [0100]    [0100]FIG. 12 represents the sequence of passing through the individual space segments  32   1  to  32   8  by the numbers 1 to 8 in the individual space segments  32 , that is to say that the pump branch  26  strikes the space segment  32   1  then, after formation of the first incident focused branch  52   1  and the first emerging defocused branch  54   1 , the formation of the branch  56   1  takes place which runs initially in the space segment  32   5  and then, after deviation by the first deviating unit  60 , in the space segment  32   8 , and so on, until finally the fourth collimated branch  56   4  strikes the second deviating unit  70  symmetrically with respect to the symmetry plane  78  and is reflected back on itself, although laterally inverted.  
         [0101]    Preferably, as clearly represented in particular by FIG. 12, the first deviating unit  60  and the second deviating unit  70  in the first exemplary embodiment are designed in such a way that, between them, a section  80  is left which corresponds to the angular extent of the first space segment  32   1 , so that the collimated pump radiation branch  26  can be guided through this section  80  to the parabolic mirror  50 .  
         [0102]    Preferably, the two deviating units  60  and  70  are designed in such a way that they have a shape which is symmetrical with respect to the symmetry plane  68  or  78 , respectively, in the simplest case the deviating unit  60  being formed by a prism  62  with a rectangular base face and the deviating unit  70  being formed by a prism  72  with side edges  82  and  84  running at an angle symmetrically with respect to the symmetry plane  78 , this angle between the side edges  82  and  84  being equal to 135° in the first exemplary embodiment.  
         [0103]    The two deviating units  60 ,  70  furthermore form a recess  86  through which the branches  52  and  54  of the pump radiation field that lead to the solid body  10  can pass, and which can also accommodate the solid body  10 .  
         [0104]    In the solution according to the invention, it is assumed that the collimated pump radiation branch  26  and the collimated sub-branches  56   1c  to  56   3c  that form the other incident branches  52   2  to  52   4 , as well as the collimated sub-branches  54   1a  to  54   4a  formed from the emerging branches  54   1  to  54   4 , do not overlap. For this reason, a separate space segment  32   1  to  32   8  is respectively to be provided for each of these collimated branches  26 ,  54   1c  to  54   3c  as well as  54   1a  to  54   4a , so that the number and extent of the space segments  32   1  to  32   8  corresponds to the number and extent of the segments  50   1  to  50   8  of the parabolic mirror  50 , and also to the number of the aforementioned collimated sub-branches, with the space segments  32  respectively stretching over the same angular spacing around the mid-axis  42 , since a cross-sectional area of the collimated branches  56  of the resonator radiation field  20  also does not change during the pass through the refocusing optics  30 .  
         [0105]    If the angle over which the respective space segments  32  stretch is reduced, then as represented in a second exemplary embodiment in FIG. 13, the number of pump transmissions through the solid body  10  is likewise greater. In this case, the second deviating unit  70 ′ is designed and arranged in such a way that it deviates the second collimated branches, and the first deviating unit  60 ′ is arranged in such a way that it deviates two collimated branches and reflects the last collimated branch however laterally inverted back on itself, since half of the latter strikes the reflection face  64  and half of it strikes the reflection face  66 .  
         [0106]    [0106]FIG. 13 now indicates, on the one hand, the number of space segments  32   1  to  32   10  and, furthermore, the sequence of passing through these is indicated in each space segment  32  by the numbers 1 to 10. In the third exemplary embodiment, the fifth collimated branch  56   5  running in the eighth space segment  32   8  is hence reflected back on itself by the reflection faces  64  and  66 .  
         [0107]    In the second exemplary embodiment, it is therefore possible to obtain 20 pump transmissions through the solid body  10 , in contrast to the 16 pump transmissions of the first exemplary embodiment.  
         [0108]    In a third exemplary embodiment, represented in FIG. 14, the number of pump transmissions is increased further, with the number of space segments  32  likewise being increased correspondingly.  
         [0109]    In the third exemplary embodiment, the first deviating unit  60 ″ is designed in such a way that it stretches over six space segments overall, namely the space segments  32   7  to  32   12 , and deviates three collimated branches  56  overall, while the second deviating unit  70 ″ is designed in such a way that it deviates two collimated branches overall and additionally reflects one back on itself.  
         [0110]    In particular, it can be seen in the third exemplary embodiment that, during the pass through the refocusing optics  30 , the collimated branch deviated first in each of the deviating units  60 ″ and  70 ″, namely the collimated branch stretching from the space segment  32   7  to the space segment  32   12 , has the greatest angular spacing between the first sub-branch  56   1a  and the third sub-branch  56   1c , while the deviated sub-branches following later, namely the collimated branches  56  stretching between the space segments  32   8  and  32   11  and between the space segment  32   9  and  32   10 , with their first sub-branch and their second sub-branch, respectively lie between the first and second sub-branch of the collimated branch previously deviated by the same deviating unit  60 ″.  
         [0111]    In a fourth exemplary embodiment, represented in FIG. 14, the number of pump transmissions can be increased to 32 by further increasing the space segments  32  to 16 overall, in which case the first deviating unit  60 ′″ deviates four collimated branches overall, while the second deviating unit  70 ′″ deviates three collimated branches and reflects one back on itself, although laterally inverted.  
         [0112]    In a fifth exemplary embodiment, represented in FIG. 16, 16 pump transmissions are provided just as in the first exemplary embodiment, so that the parabolic mirror  50  overall 8 space segments  32  are provided.  
         [0113]    In contrast to the first exemplary embodiment, however, the second deviating unit  70 ″″ is designed in such a way that it stretches merely over two space segments, namely the space segments  32   3  and  32   4 , so that the side edges  82 ″″ and  84 ″″ meet at an angle of 90°.  
         [0114]    The deviating unit  60  in the fifth exemplary embodiment is designed in the same way as in the first exemplary embodiment, and stretches over four space segments  32   5  to  32   8 .  
         [0115]    Because the second deviating unit  70 ″″ is restricted to the space segments  32   3  and  32   4 , the second collimated branch  56   2  no longer stretches between the space segments  32   2  to  32   4 , but rather between the space segments  32   3  and  32   4 , since the symmetry plane  78 ″″ meets the symmetry plane  68  at an angle α″″ of 45°.  
         [0116]    The fourth collimated branch  56   4  therefore also lies in the space segment  32   2  and, in order to reflect it back, the space segment  32   2  is allocated an end mirror  90  which is formed, for example, as a plane mirror and hence reflects the fourth collimated branch  56   4  back on itself, but not laterally inverted.  
         [0117]    The different shape of the deviating element  70 ″″ furthermore has the effect that the third collimated branch does not run from the space segment  32   6  to the space segment  32   7 , as in the first exemplary embodiment, but rather from the space segment  32   7  to the space segment  32   6 .  
         [0118]    The fifth exemplary embodiment according to FIG. 16 may then, as in a sixth exemplary embodiment represented in FIG. 17, also be expanded in order to pump two solid bodies  10   1  and  10   2 , each of the solid bodies  10  being allocated a focusing subsystem  30   1  and  30   2  which respectively has, in addition to the parabolic mirror  50  with eight segments, the first deviating unit  60  and the second deviating unit  70 ″″.  
         [0119]    In contrast to the fifth exemplary embodiment, the end mirror  90  is replaced by a deviating unit  100  which, for example, comprises a deviating prism  102  with a first reflection face  104  and a second reflection face  106 , both of which are arranged symmetrically with respect to a symmetry plane  108  that runs between the solid bodies  10  and transversely with respect to a connecting straight line between them.  
         [0120]    This deviating unit  100  provides the opportunity to transfer the fourth collimated branch  56   4  from the first focusing subsystem  30   1  to the second focusing subsystem  30   2 , and to make it run in the first space segment  32   11  there, like the collimated pump radiation branch  26 , in which case, in the same way as already described in connection with the fifth exemplary embodiment and the first exemplary embodiment, the subsequent incident, emerging and collimated branches are formed and finally the last collimated branch  56   4 ″ strikes an end mirror  90   2  in the space segment  32   22 , which corresponds to the end mirror  90  of the fifth exemplary embodiment and which makes the pump radiation field  20  that passes once through the two focusing subsystems  30   1  and  30   2  run back again in a reverse fashion.  
         [0121]    In the sixth exemplary embodiment, 16 pump transmissions are therefore obtained overall in each of the two solid bodies  10   1  and  10   2 .  
         [0122]    As an alternative to providing the deviating prism  102 , it is also conceivable to provide deviating and intermediate-focusing optics in the deviating unit, so that the optical path between the focusing subsystems  30   1  and  30   2  can be selected in an arbitrary way.  
         [0123]    In a seventh exemplary embodiment of a laser amplifier system according to the invention, represented in FIG. 18, the pumping of two solid bodies  10   1  and  10   2  likewise takes place via a focusing system  130  which, as in the first exemplary embodiment, has the deviating units  60  and  70 , the deviating unit  60  being allocated to the first solid body  10   1  and the deviating unit  70  being allocated to the second solid body  10   2  and, between these deviating units  70 , a deviating unit  140  denoted as a whole by  140  being provided, which comprises a prism  142  with two reflection faces  144  and  146  that are arranged symmetrically with respect to a symmetry plane  148 , the symmetry plane  148  stretching between the solid bodies  10  and transversely with respect to a connecting straight line between them.  
         [0124]    The reflection face  144  is in this case allocated to the space segments  32   11  to  32   41 , and it is used to couple the space segments  32   11  to  32   41  together with the space segments  32   52  to  32   82 , a reflection respectively taking place symmetrically with respect to the symmetry plane  148  which runs perpendicularly to the symmetry plane  68 .  
         [0125]    Preferably, the deviating unit  140  couples the space segments  32   52  and  32   41  as well as  32   31  and  32   62 ,  32   21  and  32   72  as well as  32   82  and  32   11 .  
         [0126]    A collimated pump branch  26  delivered in the space segment  32   12  is hence transferred via an incident and emerging branch into the space segment  32   52 , there from the as a collimated branch by the deviating unit  140  into the space segment  32   41  from the space segment  32   41  via an incident and emerging branch into the space segment  32   81 , deviated from the space segment  32   81  via the deviating unit  60  into the space segment  32   51 , from the space segment  32   51  via an incident and emerging branch into the space segment  32   11 , from the space segment  32   11  into the space segment  32   82 , from the space segment  32   82  via an incident and emerging branch into the space segment  32   42 , deviated from the space segment  32   42  by the deviating unit  70  into the space segment  32   22 , deviated from the space segment  32   22  via an incident and emerging branch into the space segment  32   62 , projected from the space segment  32   62  into the space segment  32   31  by the deviating unit  140 , from the space segment  32   31  via an incident and emerging branch into the space segment  32   71 , deviated from the space segment  32   71  by the deviating unit  60  into the space segment  32   51 , deviated from the space segment  32   51  via an incident and emerging branch into the space segment  32   21 , deviated from the space segment  32   21  by the deviating unit  140  into the space segment  32   72  and from the space segment  32   72  via an incident and emerging branch into the space segment  32   32  and reflected back on itself there laterally inverted by the deviating unit  70  in the same way as in the first exemplary embodiment, so that after the first transmission, the pump radiation field  20  again passes through the focusing system  130  with a second transmission, and therefore respectively produces sixteen pump transmissions in each of the solid bodies  10   1  and  10   2 .