U.S. patent application number 09/776177 was filed with the patent office on 2001-11-08 for laser amplification system.
This patent application is currently assigned to Universitaet Stuttgart Institut fuer Strahlwerkzuege. Invention is credited to Contag, Karsten, Erhard, Steffen, Giesen, Adolf, Karszewski, Martin, Stewen, Christian, Voss, Andreas.
Application Number | 20010038658 09/776177 |
Document ID | / |
Family ID | 7876364 |
Filed Date | 2001-11-08 |
United States Patent
Application |
20010038658 |
Kind Code |
A1 |
Contag, Karsten ; et
al. |
November 8, 2001 |
Laser amplification system
Abstract
In order to provide a laser amplification system comprising
several solid-state volumes having a laser-active medium, a pumping
radiation source, a pumping radiation reflector which allows a leg
of the pumping radiation field entering the solid-state volume to
pass through the solid-state volume again as outgoing leg such that
the incoming leg and the outgoing leg form a first pumping branch,
a first pumping radiation path, in which the pumping radiation
field passes through the first pumping branches in a first
sequence, with which the individual solid-state volumes are acted
upon with pumping power as uniformly as possible, it is suggested
that each solid-state volume be penetrated by a second pumping
branch, the incoming leg of which and the outgoing leg of which are
located in a second plane different to the first plane, that a
second pumping radiation path be provided, in which the pumping
radiation field passes through the second pumping branches in a
second sequence and that in the second sequence the order of the
solid-state volumes be changed in relation to the first
sequence.
Inventors: |
Contag, Karsten; (Stuttgart,
DE) ; Erhard, Steffen; (Fellbach, DE) ;
Giesen, Adolf; (Renningen, DE) ; Karszewski,
Martin; (Bondorf, DE) ; Stewen, Christian;
(Aichach, DE) ; Voss, Andreas; (Schramberg,
DE) |
Correspondence
Address: |
LAW OFFICE OF BARRY R LIPSITZ
755 MAIN STREET
MONROE
CT
06468
US
|
Assignee: |
Universitaet Stuttgart Institut
fuer Strahlwerkzuege
Pfaffenwaldring 43
Stuttgart
DE
70569
|
Family ID: |
7876364 |
Appl. No.: |
09/776177 |
Filed: |
February 2, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09776177 |
Feb 2, 2001 |
|
|
|
PCT/EP99/05128 |
Jul 19, 1999 |
|
|
|
Current U.S.
Class: |
372/70 |
Current CPC
Class: |
H01S 3/09415 20130101;
H01S 3/0604 20130101; H01S 3/0813 20130101; H01S 3/07 20130101;
H01S 3/094084 20130101 |
Class at
Publication: |
372/70 |
International
Class: |
H01S 003/091; H01S
003/092 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 4, 1998 |
DE |
198 35 108.9 |
Claims
1. Laser amplification system comprising several solid-state
volumes having a laser-active medium, a pumping radiation source
for generating a pumping radiation field for the optical pumping of
the laser-active medium, a pumping radiation reflector associated
with each solid-state volume, said reflector allowing a leg of the
pumping radiation field entering the solid-state volume to pass
through the solid-state volume again as an outgoing leg, that the
incoming leg and the outgoing leg form an angle with one another
located in a first plane and form a first pumping branch, a first
pumping radiation path through the solid-state volumes, the first
pumping branches being arranged in said path so as to follow one
another such that the pumping radiation field passes through the
several solid-state volumes in a first sequence, characterized in
that each solid-state volume is penetrated by a second pumping
branch (138), the incoming leg (132) and the outgoing leg (134) of
said pumping branch being located in a second plane (136) different
to the first plane (36) and forming an angle in this, that a second
pumping radiation path (138.sub.1 to 138.sub.4) is provided, the
second pumping branches (138) of the several solid-state volumes
(10) being arranged in said path so as to follow one another such
that the pumping radiation field passes through the solid-state
volumes (10) in a second sequence.
2. Laser amplification system as defined in claim 1, characterized
in that in the second sequence the order of the solid-state volumes
(10) is changed in relation to the first sequence.
3. Laser amplification system as defined in claim 1 or 2,
characterized in that each of the pumping radiation paths (38.sub.1
to 38.sub.4; 138.sub.1 to 138.sub.4) is supplied by its own pumping
radiation source (28, 128).
4. Laser amplification system as defined in claim 1 or 2,
characterized in that the pumping radiation paths (38.sub.1 to
38.sub.4; 138.sub.1 to 138.sub.4) are supplied by a single pumping
radiation source (28).
5. Laser amplification system as defined in claim 4, characterized
in that the pumping radiation paths (38.sub.1 to 38.sub.4;
138.sub.1 to 138.sub.4) are coupled to one another by an optical
deflection means (60).
6. Laser amplification system as defined in any one of the
preceding claims, characterized in that the pumping radiation field
passes through each pumping radiation path (38.sub.1 to 38.sub.4;
138.sub.1 to 138.sub.4) in two opposite directions.
7. Laser amplification system as defined in claim 6, characterized
in that a reflector (50.sub.4, 150.sub.4) reflecting back the
pumping radiation field is associated at one end of each pumping
radiation path.
8. Laser amplification system as defined in any one of the
preceding claims, characterized in that in the second sequence the
order of the solid-state volumes (10) is reversed in relation to
the first sequence.
9. Laser amplification system as defined in any one of the
preceding claims, characterized in that at least one additional
pumping radiation path (238.sub.1 to 238.sub.4; 338.sub.1 to
338.sub.4) is provided, the pumping radiation field (230, 330)
passing through the solid-state volumes (10) with said path in the
form of at least one additional sequence (238.sub.1 to 238.sub.4;
338.sub.1 to 338.sub.4).
10. Laser amplification system as defined in claim 9, characterized
in that the at least one additional sequence (238.sub.1 to
238.sub.4; 338.sub.1 to 338.sub.4) runs such that this counteracts
varying pumping excitations of the laser-active material in the
solid-state volume (10) as a result of the first and the second
sequence.
11. Laser amplification system as defined in any one of the
preceding claims, characterized in that the individual pumping
branches (38.sub.1 to 38.sub.4; 138.sub.1 to 138.sub.4) of a
pumping radiation path are coupled by optical refocusing means (50,
510).
12. Laser amplification system as defined in claim 11,
characterized in that the optical refocusing means (50, 150)
reshape the outgoing leg (34, 134) of a pumping branch directly
into the corresponding one of the incoming legs (32, 132) of the
next pumping branch.
13. Laser radiation system as defined in claim 11, characterized in
that at least one of the optical refocusing means (50', 150') is
designed as an intermediately collimating optical refocusing means
(50', 150') and reshaping the respective outgoing leg (34) via an
intermediately collimated leg (54, 154) into the corresponding
incoming leg (32).
14. Laser amplification system as defined in claim 13,
characterized in that the intermediately collimating optical
refocusing means (50', 150') have a folded, collimated leg (54,
154).
15. Laser amplification system as defined in claim 14,
characterized in that the intermediately collimating optical
refocusing means (50', 150') have a deflection element (56) for
folding the intermediately collimated leg (54, 154).
16. Laser amplification system as defined in claim 15,
characterized in that one of the optical refocusing means (50',
150') of the first and one of the second pumping radiation path
each image the respective intermediately collimated leg onto a
common deflection element (56).
17. Laser amplification system as defined in any one of claims 13
to 16, characterized in that the intermediately collimating optical
refocusing means (50', 150') have a collimating element (52, 152)
reshaping the respectively outgoing leg (34, 134) into the
intermediately collimated leg (54, 154).
18. Laser amplification system as defined in any one of claims 13
to 16, characterized in that the intermediately collimating optical
refocusing means (50', 150') have a focusing element (58, 158)
imaging the intermediately collimated leg (54, 154) into the
respectively incoming leg (34, 134).
19. Laser amplification system as defined in any one of the
preceding claims 10 to 17, characterized in that the optical
refocusing means (50, 150) comprise hollow mirrors.
20. Laser amplification system as defined in claim 19,
characterized in that the hollow mirrors are designed as
non-spherical mirrors.
21. Laser amplification system as defined in claim 20,
characterized in that the hollow mirrors are designed as elliptical
mirrors.
22. Laser amplification system as defined in claim 20,
characterized in that the hollow mirrors are designed as parabolic
mirrors.
23. Laser amplification system as defined in claim 20,
characterized in that the hollow mirrors are designed as toric
mirrors.
24. Laser amplification system as defined in any one of the
preceding claims, characterized in that the solid-state volumes
(10) are arranged along a line (12).
25. Laser amplification system as defined in any one of the
preceding claims, characterized in that all the reflection surfaces
(17) of the reflectors (16) associated with the solid-state volumes
(10) are located in a common plane.
26. Laser amplification system as defined in claim 25,
characterized in that the refocusing elements (50, 150) are located
on different sides of a surface (13) extending at right angles to
the reflection surfaces (17) and through the line (12).
27. Laser amplification system as defined in any one of the
preceding claims, characterized in that the planes (36, 136) where
the first and second pumping branches (38, 138) are located
intersect at an angle of smaller than or equal to 90.degree..
28. Laser amplification system as defined in any one of the
preceding claims, characterized in that the planes (36, 136) where
the first and second pumping branches (38, 138) are located extend
transversely to one another.
29. Laser amplification system as defined in any one of the
preceding claims, characterized in that the several solid-state
volumes having laser-active medium are arranged in several
solid-state bodies.
30. Laser amplification system as defined in claim 29,
characterized in that each solid-state volume having laser-active
medium is arranged in its own solid-state body.
Description
[0001] The present disclosure relates to the subject matter
disclosed in International Application No. PCT/EP99/05128 (WO
00/08726) of Jul. 19, 1999, the entire specification of which is
incorporated herein by reference.
[0002] The invention relates to a laser amplification system
comprising several solid-state volumes having a laser-active
medium, a pumping radiation source for generating a pumping
radiation field for the optical pumping of the laser-active medium,
a pumping radiation reflector which is associated with each
solid-state volume and allows a leg of the pumping radiation field
entering the solid-state volume to pass through the solid-state
volume again as an outgoing leg such that the incoming leg and the
outgoing leg form an angle with one another located in a plane and
thereby form a first pumping branch, a first pumping radiation path
through the solid-state volumes, in which the first pumping
branches are arranged so as to follow one another such that the
pumping radiation field passes through the several solid-state
volumes in a first sequence.
[0003] Laser amplification systems of this type are known, for
example, from EP 0 632 551.
[0004] In the case of laser amplification systems with solid-state
volumes having a laser-active medium the problem exists that a
pumping light excitation of the individual solid-state bodies is
brought about with varying pumping power.
[0005] The object underlying the invention is therefore to provide
a laser amplification system with several solid-state volumes, with
which the individual solid-state volumes are acted upon with
pumping power as uniformly as possible.
[0006] This object is accomplished in accordance with the
invention, in a laser amplification system of the type described at
the outset, in that each solid-state volume is penetrated by a
second pumping branch, the incoming leg of which and the outgoing
leg of which are located in a second plane different to the first
plane and in this form an angle with one another, that a second
pumping radiation path is provided, in which the second pumping
branches of the several solid-state volumes are arranged so as to
follow one another such that the pumping radiation field passes
through the solid-state volumes in a second sequence.
[0007] The advantage of the inventive solution is to be seen in the
fact that with the second pumping radiation path the possibility is
created of pumping each of the solid-state volumes with the same
number of pumping branches and, in addition, of introducing the
pumping power in the solid-state volumes to be pumped as uniformly
as possible on account of the fact that the two pumping branches
are located in different planes.
[0008] This has the advantage, in particular, with a view to the
type of thin, disk-shaped solid-state bodies, which are provided in
the inventive solution and are preferably located with a flat side
on a cooling surface, that, as a result, the design of as uniform a
temperature curve as possible with planes of essentially the same
temperature extending parallel to the flat sides of the solid-state
bodies is facilitated which is essential for the advantageous
working within the scope of the inventive concept.
[0009] It is particularly favorable when in the second sequence the
order of the solid-state bodies is changed in relation to the first
sequence. This solution allows the reduction in intensity in the
sequence to be counteracted as a result of the changed order.
[0010] With respect to the type of supply to the first and second
pumping radiation paths, no further details have so far been given.
One advantageous embodiment, for example, provides for each of the
pumping light radiation paths to be supplied by its own pumping
radiation source, wherein it is preferably provided for the pumping
radiation sources to have essentially the same power.
[0011] Another alternative embodiment provides for the pumping
radiation paths to be supplied by a single pumping radiation
source. This has the advantage that--insofar as the radiation power
of a single pumping radiation source is sufficient--this can be
used for both pumping radiation paths.
[0012] In this respect, there are different possibilities for
realizing the supply to the two pumping radiation paths with one
pumping radiation source.
[0013] One possibility is for the pumping radiation field from the
pumping radiation source to be divided between the two pumping
radiation paths by a beam divider.
[0014] This solution has the advantage that, as a result, the
possibility exists of supplying both pumping radiation paths with
pumping radiation fields of essentially the same intensity.
[0015] Another advantageous solution provides for the pumping
radiation paths to be coupled to one another by an optical
deflection means, i.e. for the pumping radiation field to be
coupled in by an optical deflection means with the intensity which
is present at the end of one of the pumping radiation paths such
that this supplies the next pumping radiation path. This solution
is particularly expedient when the intensity absorbed per pumping
radiation path is not very large and so following the first pumping
radiation path a power of the pumping radiation field is
nevertheless available which is sufficiently large to supply the
second pumping radiation path.
[0016] In principle, it is provided within the scope of the
inventive solution for the pumping radiation field to pass through
each pumping radiation path in one direction. To improve the
pumping of the solid-state bodies it is, however, also advantageous
when the pumping radiation field passes through each pumping
radiation path in two opposite direction. This is irrespective of
whether two pumping radiation sources are provided for supplying
the pumping radiation paths or only one pumping radiation source,
the power of which can be coupled into the pumping radiation paths
in the different ways already described.
[0017] A solution, which is particularly simple to realize and with
which the pumping radiation field passes through each pumping
radiation path twice, provides for a reflector to be arranged at
one end of each pumping radiation path and for this to reflect back
the pumping radiation field exiting from the pumping radiation
path.
[0018] In conjunction with the preceding solutions it has merely
been specified that the order of the solid-state volumes in the
second sequence is intended to be different to that in the first
sequence. This may be realized in the most varied of ways, in
particular, in a different manner when not only a first sequence
and a second sequence are provided but rather several sequences
exceeding the first and the second sequences. In the simplest case
of a first and a second sequence it is, however, preferably
provided for the order of the solid-state volumes in the second
sequence to be reversed in relation to the first sequence.
[0019] So far, it has been specified in conjunction with the
inventive solution that there is a first pumping radiation path and
a second pumping radiation path. The inventive solution is,
however, not limited to two pumping radiation paths with first and
second pumping branches, respectively. On the contrary, it is
possible in a further inventive solution for at least one
additional pumping radiation path to be provided, with which the
pumping radiation field passes through the solid-state bodies in
the form of at least one additional sequence. The advantage of this
solution is to be seen in the fact that with it an even more
uniform excitation of the solid-state bodies can be realized.
[0020] This may be realized particularly favorably when the at
least one additional sequence runs such that this counteracts
varying pumping excitations of the laser-active material in the
solid-state volume as a result of the first and the second
sequences.
[0021] It is, in particular, advantageous when the number of
pumping radiation paths is an even number so that the fact that
with each pumping radiation path the pumping radiation field pumps
from the one pumping branch to the other pumping branch with lower
power can be compensated particularly favorably.
[0022] With respect to the manner, in which the individual pumping
branches of one pumping radiation path are coupled, no particular
details have been given. One advantageous embodiment, for example,
provides for the individual pumping branches of a pumping radiation
path to be coupled by optical refocusing means.
[0023] These optical refocusing means may be designed in the most
varied of ways. One type of design provides, for example, for the
optical refocusing means to image the outgoing leg of a pumping
branch directly into the corresponding incoming leg of the next
pumping branch.
[0024] The advantage of this solution lies in its simplicity. These
solutions do, however, have the problem that either the pumping
light radiation spot is increased in size or a cross section of the
pumping radiation field becomes ever larger from optical refocusing
means to optical refocusing means.
[0025] For this reason, one inventive solution which is improved in
this respect provides for at least one of the optical refocusing
means to be designed as an intermediately collimating optical
refocusing means and to image the respective outgoing leg via an
intermediately collimated leg into the corresponding incoming leg.
This solution has the advantage that as a result of the
intermediate collimation it is possible to avoid any increase in
the size of the cross section of the pumping radiation field.
[0026] In this respect, the intermediately collimated legs are
preferably designed such that their imaging corresponds to the
imaging which is obtained with the sum of the focal distances of
the optical means provided on both sides of the intermediately
collimated leg. In the case of optical means having the same focal
distance on both sides of the intermediately collimated leg, the
imaging of the intermediately collimated leg corresponds to one
with a double focal distance.
[0027] In this respect, it is particularly favorable when all the
optical refocusing means are designed as intermediately collimating
optical refocusing means so that during the entire course of the
respective pumping radiation path no appreciable increase in the
size of the cross section of the pumping radiation field is brought
about and thus the necessity also does not exist of not imaging
part of the radiation field or adapting the optical refocusing
means to the increasing size of the cross section of the pumping
radiation fields.
[0028] One particularly advantageous realization of an
intermediately collimating optical refocusing means provides for
this to have a folded collimated leg. Such a folded collimated leg
creates, in particular, the possibility of designing the optical
refocusing means to be space-saving.
[0029] Furthermore, a folding of the collimated leg creates the
possibility of arranging the legs entering the respective
solid-state bodies such that these always enter the solid-state
volumes from the same side thereof.
[0030] With respect to the design of the intermediately collimating
optical refocusing means, no particular details have so far been
given. It is, for example, favorable for generating a folded
collimated leg when the intermediately collimating optical
refocusing means have a deflection element for the folding of the
intermediately collimated leg.
[0031] To save on components in the case of the intermediately
collimating optical refocusing means which require many components,
it is preferably provided for one of the intermediately collimating
optical refocusing means of the first and one of the intermediately
collimating optical refocusing means of the second pumping
radiation path to each image the respective, intermediately
collimated leg onto a common deflection element so that only one
deflection element is required for every two optical refocusing
means.
[0032] Furthermore, no further details have been given with respect
to the design of the intermediately collimating optical refocusing
means as a whole. It is, for example, favorably provided for the
intermediately collimating optical refocusing means to have a
collimating element which images the respectively outgoing leg into
the intermediately collimated leg.
[0033] Furthermore, it is favorable when the intermediately
collimating optical refocusing means have a focusing element which
images the intermediately collimated leg into the respectively
incoming leg.
[0034] With respect to the optical elements which are used in the
optical refocusing means, no further details have so far been
given.
[0035] With respect to the simplicity in construction and spatial
requirements, it has proven to be particularly advantageous when
the optical refocusing means comprise hollow mirrors, wherein the
hollow mirrors serve, in particular, to reshape the outgoing legs
of a pumping branch directly into the corresponding incoming legs
of the next pumping branch or serve to act as collimating and
focusing elements.
[0036] In order to obtain particularly good optical images, it is
preferably provided for the hollow mirrors to be designed as
non-spherical mirrors since with spherical mirrors a not
inconsiderable distortion always occurs which deteriorates too
greatly the quality of the optical imaging with multiple reshaping
of the pumping radiation field.
[0037] One embodiment, in particular, in the case of hollow mirrors
which reshape an outgoing leg of a pumping branch directly into an
incoming leg of the next pumping branch provides for the hollow
mirrors to be designed as elliptical mirrors; with the elliptical
shape of the mirrors a good quality of the optical imaging can be
achieved with adaptation of the shape.
[0038] Another alternative embodiment, in particular, one, with
which the hollow mirror is intended to represent a collimating or
focusing element, provides for the hollow mirror to be designed as
a parabolic mirror since a parabolic mirror is always in a position
to focus a collimated leg or, vice versa, to collimate a divergent
leg.
[0039] Not only the use of elliptical mirrors but also the use of
parabolic mirrors entails considerable costs since these mirrors
are complicated to produce.
[0040] For this reason, one advantageous solution provides for the
hollow mirrors to be designed as toric mirrors. Toric mirrors of
this type can replace not only elliptical mirrors but also
parabolic mirrors, wherein the quality of the optical imaging is
still sufficiently good, in particular, in the case of long focal
distances.
[0041] With respect to the arrangement of the solid-state volumes
relative to one another, no further details have been given. In
principle, the most varied of arrangements of the solid-state
volumes relative to one another would be conceivable. The inventive
concept may be realized constructionally in a particularly
favorable manner when the solid-state volumes are arranged along a
line, wherein the line can, in principle, be a curved or a straight
line. The individual optical refocusing means may be arranged in a
particularly space-saving manner when the solid-state volumes are
arranged along a straight line.
[0042] Furthermore, it is preferably provided for all the
reflection surfaces of the reflectors associated with the
solid-state volumes to be located in a common plane. In this case,
the first and second pumping branches of the pumping radiation
field then extending through the solid-state volumes are located in
planes which are at right angles to the common plane of the
reflection surfaces of all the reflectors.
[0043] In this case, the refocusing elements may preferably be
arranged on different sides of a surface extending at right angles
to the reflection surfaces and through the line, wherein one
pumping branch of the pumping radiation field preferably extends
between a refocusing element located on one side of the surface to
a refocusing element located on the other side of the surfaces.
[0044] With respect to the different planes, in which the first and
second pumping branches are intended to be located, no further
details have likewise been given so far. One advantageous
embodiment, for example, provides for the planes, in which the
first and second pumping branches are located, to intersect at an
angle of less than or equal to 90.degree..
[0045] With respect to the arrangement of the solid-state volumes,
no further details have been given in conjunction with the
preceding explanations concerning the individual embodiments. It
would, for example, be conceivable, in particular, with a spatially
very small design of the inventive solution to provide all the
solid-state volumes in one solid-state body. For reasons of the
spatial design it is advantageous, in particular, in the case of
great power and thus large solid-state volumes when the several
solid-state volumes having laser-active medium are arranged in
several solid-state bodies, wherein a plurality of solid-state
volumes can still be provided in each solid-state body.
[0046] It is advantageous, in particular, when achieving great
power when each solid-state volume having laser-active medium is
arranged in its own solid-state body so that an optimum cooling is
brought about in the respective solid-state body, in particular, in
the case of great power.
[0047] Additional features and advantages of the invention are the
subject matter of the following description as well as the drawings
illustrating several embodiments.
[0048] In the drawings:
[0049] FIG. 1 shows a schematic plan view of an inventive laser
amplification system in the direction of arrow A in FIG. 2 with a
schematically indicated course of the pumping branches and pumping
radiation paths;
[0050] FIG. 2 shows a perspective, schematic illustration of the
first embodiment of the inventive laser amplification system
illustrated in FIG. 1 with a first pumping radiation path
illustrated spatially and a second pumping radiation path
illustrated by a dash-dot central line;
[0051] FIG. 3 shows an illustration similar to FIG. 1 of a second
embodiment;
[0052] FIG. 4 shows an illustration similar to FIG. 1 of a third
embodiment with intermediately collimating refocusing elements;
[0053] FIG. 5 shows a schematic perspective illustration of the
third embodiment according to FIG. 4 with a first pumping radiation
path drawn in in full and a second pumping radiation path indicated
by dash-dot central lines;
[0054] FIG. 6 shows a schematic perspective illustration of a laser
resonator of the third embodiment without illustration of the
pumping radiation field and
[0055] FIG. 7 shows a schematic illustration similar to FIG. 1 of a
fourth embodiment of the inventive solution.
[0056] A first embodiment of an inventive laser amplification
system illustrated in FIGS. 1 and 2 comprises several solid-state
bodies 10, in this case the solid-state bodies 10.sub.1 to 10.sub.4
which are arranged, for example, along a line 12 which can be not
only a straight line but also a curved line. Each of the
solid-state bodies 10 has a laser-active medium to be pumped with a
pumping radiation field in a solid-state volume area thereof.
[0057] Each of the solid-state bodies 10 is designed as a flat disk
with two slightly curved or planar flat sides located opposite one
another and rests with a rearward flat side 14 on a respective
reflector 16 which is arranged, for its part, on a cooling finger
18 so that cooling of the solid-state body 10 is brought about by
the cooling finger 18 via the reflector 16.
[0058] The pumping radiation field passes, on the one hand, through
the front flat side 20 into the solid-state body 10 in order to
pump the laser-active medium and, on the other hand, the laser
radiation also exits through the front flat side 20, the guidance
of the laser radiation not being illustrated in detail in FIGS. 1
and 2 for reasons of clarity.
[0059] In accordance with the invention, the reflector 16 is
designed such that it reflects at least the pumping radiation field
but preferably the laser radiation which is forming as well.
[0060] With respect to the type of design of the solid-state body
10 and the type of pumping of the solid-state body 10, the
arrangement of the reflector 16 and the cooling finger 18 reference
is made in full to EP 0 632 551.
[0061] The pumping radiation field 30 forms, as illustrated in
FIGS. 1 and 2, a leg 32.sub.1 of the pumping radiation field 30
which enters the solid-state body 10.sub.1, is reflected by the
reflector 16 after passing through the solid-state body 10 and as
outgoing leg 34.sub.1 penetrates the solid-state body once more
from the side of the reflector 16.
[0062] The incoming leg 32.sub.1 and the outgoing leg 34.sub.1
extend parallel and symmetrically to a plane 36 and form a pumping
branch for the first solid-state body 10.sub.1 designated as a
whole as 38.sub.1.
[0063] The incoming leg 32.sub.1 is preferably focused onto the
solid-state body 10, for example, by means of an optical focusing
means 40 which focuses an incoming collimated leg 42 of the pumping
radiation field 30 onto the desired pumping light spot in the area
of the solid-state body 10.
[0064] The outgoing leg 34.sub.1 extends divergently proceeding
from the solid-state body 10 and impinges on an optical refocusing
means which is designated as a whole as 50 and, in the simplest
case as illustrated in FIG. 2, is designed as a refocused mirror,
preferably, as a refocused hollow mirror which images the outgoing
leg 34.sub.1 into an incoming leg 32.sub.2 for the solid-state body
10.sub.2, from which an outgoing leg 34.sub.2 then exits again
which, for its part, impinges on the optical refocusing means
50.sub.2 which again images the outgoing leg 34.sub.2 into an
incoming leg 32.sub.3 which enters the solid-state body 10.sub.3
and is again reflected by the corresponding reflector 16.sub.3 and
impinges as outgoing leg 34.sub.3 on a third optical refocusing
means 50.sub.3 which images the outgoing leg 34.sub.3 into an
incoming leg 32.sub.4 which impinges on the solid-state body
10.sub.4, is reflected by the reflector 16.sub.4 thereof and exits
from the solid-state body 10 as outgoing leg 34.sub.4.
[0065] The incoming leg 32.sub.2 and the outgoing leg 34.sub.2
together form a pumping branch 38.sub.2 following the pumping
branch 38.sub.1; subsequently, the formation of a further pumping
branch 38.sub.3 is brought about, formed by the incoming leg
32.sub.3 and the outgoing leg 34.sub.3, and, finally, the formation
of a further pumping branch 38.sub.4 by the incoming leg 32.sub.4
and the outgoing leg 34.sub.4.
[0066] All the pumping branches 38.sub.1 to 38.sub.4 have the
pumping radiation field passing through them one after the other in
series, wherein the corresponding planes 36.sub.1 to 36.sub.4 each
form with one another an angle of .ltoreq.180.degree.. For example,
in this case, the optical refocusing means 50.sub.1 to 50.sub.3 are
arranged alternatingly with respect to the line 12.
[0067] With such a row of pumping branches 38.sub.1 to 38.sub.4,
the laser-active medium in the four solid-state bodies 10.sub.1 to
10.sub.4 can be pumped at the same time, wherein the pumping
intensity in the laser-active mediums of the individual solid-state
bodies 10 of the row does, however, decrease successively since,
for example, the first solid-state body 10.sub.1 already absorbs
part of the intensity of the incoming leg 32.sub.1 up to the time
this impinges on the reflector 16 and so the outgoing leg 34.sub.1
already has a smaller intensity at its point of exit on the
reflector 16 and this intensity is decreased further on account of
it passing through the solid-state body 10 again.
[0068] Following the first leg 38.sub.1, the pumping radiation
field reduced with respect to its intensity is again focused by the
optical refocusing means 50.sub.1 onto the second solid-state body
10.sub.2 in the form of the incoming leg 32.sub.2 onto the
solid-state body 10.sub.2, wherein the intensity of the pumping
radiation field again decreases in the second pumping branch
38.sub.2 as it passes twice through the solid-state body 10.sub.2
and so at the end of the second pumping branch 38.sub.2 an
intensity for the pumping of the third solid-state body 10.sub.3 is
available which is already reduced due to passing, altogether, four
times through a solid-state body 10, wherein the pumping of the
third solid-state body 10.sub.3 again absorbs intensity on account
of passing twice through the solid-state body and, finally, the
intensity available in the fourth pumping branch 38.sub.4 for the
pumping of the solid-state body 10.sub.4 is already reduced on
account of passing 6 times through one of the solid-state bodies
10.sub.1 to 10.sub.4.
[0069] Once the pumping radiation field has passed through all four
solid-state bodies 10.sub.4 with the legs 38.sub.1 to 38.sub.4
within the scope of first pumping radiation path, an appreciable
intensity still remains, as a rule, in the outgoing leg 34.sub.4
and so the opportunity presents itself to design the optical
refocusing means 50.sub.4 such that this reverses the course of the
light in the first pumping radiation path and reflects the outgoing
leg 34.sub.4 back into itself so that, altogether, the pumping
radiation field passes through all the pumping branches 38.sub.4,
38.sub.3, 38.sub.2 and 38.sub.1 in the reverse order and thus the
solid-state bodies 10.sub.4, 10.sub.3, 10.sub.2 and 10.sub.1 are
pumped again in this order.
[0070] As a result, the possibility is already created on account
of the first pumping radiation path of pumping four solid-state
bodies 10.sub.1 to 10.sub.4 with four respective passes of the
pumping radiation field.
[0071] In order, in the case of four solid-state bodies 10.sub.1 to
10.sub.4, to have available for the laser-active medium a pumping
power density which is of as equal a size as possible in each of
the solid-state bodies 10.sub.1 to 10.sub.4, a second pumping
radiation path is generated in accordance with the invention and
this is formed, proceeding from an incoming collimated pumping
radiation field 142, via an optical focusing means 140 by a pumping
radiation field which forms an incoming leg 132.sub.1 proceeding
from the optical focusing means 140, this leg entering the
solid-state body 10.sub.4 and being reflected by its reflector
16.sub.4 into the outgoing leg 134.sub.1. This is reflected by
means of an optical refocusing means 150.sub.1 into an incoming leg
132.sub.2 which enters the solid-state body 10.sub.3, is reflected
by its reflector 16.sub.3 in the form of an outgoing leg 134.sub.2
and impinges on an optical refocusing means 150.sub.2 which, again,
images this into an incoming leg 132.sub.3 which enters the
solid-state body 10.sub.2, is reflected by its reflector 16.sub.2
and impinges as outgoing leg 134.sub.3 on an optical refocusing
means 150.sub.3 which forms an incoming leg 132.sub.4 which enters
the solid-state body 10.sub.1, is reflected by its reflector
16.sub.1 and impinges as outgoing leg 134.sub.4 on an optical
refocusing means 150.sub.4 which is, for example, likewise designed
as a mirror reversing the course of the light.
[0072] As a result, the second pumping radiation path comprises
analogously to the first the pumping branches 138.sub.1, 138.sub.2,
138.sub.3 and 138.sub.4 which do, however, in their order impinge
on the solid-state bodies 10.sub.1 to 10.sub.4 with a reverse order
to the pumping branches 38.sub.1 to 38.sub.4 so that the
solid-state body 10.sub.4 is pumped the most by the second pumping
radiation path and the absorbed pumping power successively
decreases as far as the solid-state body 10.sub.1 whereas the first
solid-state body 10.sub.1 is pumped the most by the first pumping
radiation path and the absorbed pumping power successively
decreases as far as the solid-state body 10.sub.4.
[0073] Furthermore, the pumping branches 138.sub.1 to 138.sub.4 are
located in planes 136.sub.1 to 136.sub.4 which do not coincide with
the planes 36.sub.1 to 36.sub.4 in the respective area of the
respective solid-state body 10.sub.1 to 10.sub.4, preferably extend
at an angle to one another so that each of the solid-state bodies
10.sub.1 to 10.sub.4 is penetrated by two pumping branches located
in different planes, namely a first pumping branch 38 and a second
pumping branch 138, and is pumped in two different directions by a
reflected pumping radiation field on account of these planes 36 and
136, respectively, extending at an angle to one another, wherein
the planes 36 and 136 preferably extend transversely to one another
in the area of the respective solid-state body 10, even better at
an angle in the order of magnitude of 90.degree., in order to bring
about a distribution of the pumping radiation field in the
respective solid-state body 10.sub.1 to 10.sub.4 which is as
symmetrical as possible with respect to a point of intersection S
of the planes 36, 136.
[0074] The inventive laser amplification system may be constructed
particularly compactly when the reflectors 16.sub.1 to 16.sub.4
have reflection surfaces 17.sub.1 to 17.sub.4 which extend in a
common plane and when a plane of symmetry 13 extends through the
line 12 and is at right angles to the reflector surfaces 17.sub.1
to 17.sub.4 and the optical refocusing means 50.sub.1 to 50.sub.4
as well as 150.sub.1 to 150.sub.4 are arranged on both sides of the
plane 13. Optical refocusing means located opposite one another in
pairs, for example, the optical refocusing means 50.sub.1 and
150.sub.3, 150.sub.2 and 50.sub.2 as well as 50.sub.3 and
150.sub.1, preferably alternate with solid-state bodies 10 in
longitudinal direction of the line 12, i.e. the solid-state body
10.sub.1 is followed, when observed along the line 12, by the pair
of optical refocusing means 50.sub.1 and 150.sub.3, the solid-state
body 10.sub.2 then follows, then the pair of optical refocusing
means 150.sub.2 and 50.sub.2, then the solid-state body 10.sub.3,
then the pair of optical refocusing means 50.sub.3 and 150.sub.1
and, finally, the solid-state body 10.sub.4.
[0075] In the inventive solution, the lines of intersection of the
planes 36 and 136 are preferably placed such that they are located
as centrally as possible in relation to the solid-state bodies
10.sub.1 to 10.sub.4 and the line 12, along which the solid-state
bodies 10.sub.1 to 10.sub.4 are arranged, preferably extends
through the lines of intersection S of the respective planes 36 and
136 in the respective solid-state bodies 10.sub.1 to 10.sub.4.
[0076] In the first embodiment illustrated in FIGS. 1 and 2, two
different pumping radiation sources are, for example, provided for
generating the two pumping radiation fields 30 and 130. There is,
however, also the possibility of dividing the pumping radiation
field of one pumping radiation source and of guiding this to the
respective optical focusing means 40 and 140 via light guides.
[0077] In a second embodiment, illustrated in FIG. 3, the optical
refocusing means 50.sub.4 is not designed such that it reflects the
outgoing leg 34.sub.4 back into itself but rather deflects the
outgoing leg 34.sub.4 onto a deflection mirror 60 which images this
onto an optical refocusing means 62 again which replaces the
optical focusing means 140 and again forms the incoming leg
132.sub.1 which is, in the long run, formed from the outgoing leg
34.sub.4 due to deflection by the optical deflection means 60 and
the optical refocusing means 62.
[0078] As for the rest, the second embodiment is identical to the
first and so reference can be made in full to the explanations
hereto.
[0079] In this embodiment, the second pumping branches 138.sub.1 to
138.sub.4 do, however, each have a smaller intensity than the first
pumping branches 38.sub.1 to 38.sub.4 since the initial intensity
of the incoming leg in the second pumping radiation path with the
pumping branches 138.sub.1 to 138.sub.4 corresponds to the final
intensity of the outgoing leg 34.sub.4 of the first pumping light
path with the pumping branches 38.sub.1 to 38.sub.4.
[0080] Nevertheless, a pumping of each of the solid-state bodies
10.sub.1 to 10.sub.4 can be brought about in the second embodiment
according to FIG. 3 in the two planes 36 and 136 extending
transversely to one another.
[0081] In a third embodiment of an inventive laser amplification
system, illustrated in FIGS. 4 to 6, the solid-state bodies
10.sub.1 to 10.sub.4 are likewise arranged along the line 12.
[0082] In contrast to the first embodiment and to the second
embodiment each of the optical refocusing means 50.sub.1 to
50.sub.3 comprises not only no hollow mirror which images the
outgoing leg 34.sub.1 of the first pumping branch 38.sub.1 onto the
incoming leg 32.sub.2 of the second pumping branch 38.sub.2 but
rather a collimating element 52.sub.1 which images the outgoing leg
34.sub.1 into a first partial leg 54a of a collimated leg 54, an
optical deflection means 56 which images the first collimated
partial leg 54a into a second collimated partial leg 54b and an
optical focusing means 58 which images the second collimated
partial leg 54b into the incoming leg 32.sub.2.
[0083] The optical refocusing means 50.sub.2 and 50.sub.3 are
designed in the same way.
[0084] In this respect, the principle is maintained in the same way
as in the first embodiment that the respective solid-state bodies
10.sub.1 to 10.sub.4 are penetrated by a first pumping branch
38.sub.1 to 38.sub.4 of the first pumping radiation path of the
pumping radiation field 30.
[0085] The optical refocusing means 150.sub.1 to 150.sub.3 also
collimate the outgoing leg 134.sub.1 by means of a collimating
element 152.sub.1 which forms a partial leg 154a of a collimated
leg 154.sub.1 which is imaged via the deflection element 56 into
the second partial leg 154 of each collimated leg 154.sub.1 and
impinges on the focusing element 158.sub.1 which images the second
partial leg 154b into the incoming leg 132.sub.2 which enters the
solid-state body 10.sub.3.
[0086] The remaining optical refocusing means 150.sub.2 and
150.sub.3 are designed in the same way.
[0087] Furthermore, a resonator designated as a whole as 70 is
provided in the third embodiment, as illustrated in FIG. 6, and its
resonator radiation field 72 penetrates all the solid-state bodies
10.sub.1 to 10.sub.4. The resonator 70 has two end mirrors 74 and
76 for forming the resonator radiation field 72 and deflection
mirrors 76.sub.1 to 76.sub.3 arranged, in addition, between the
solid-state bodies 10.sub.1 to 10.sub.4 while, in addition, the
reflectors 16.sub.1 to 16.sub.4 associated with the individual
solid-state bodies 10.sub.1 to 10.sub.4 are likewise effective at
the same time as deflection mirrors of the resonator 70 and also
reflect the resonator radiation field 72 so that this extends, for
example, from the end mirror 74 to the reflector 16.sub.1, from
this to the deflection mirror 76.sub.1, from this to the reflector
16.sub.2, from this to the deflection mirror 76.sub.2, from this to
the reflector 16.sub.3, from this to the deflection mirror 76.sub.3
and from this to the reflector 16.sub.4 and then to the end mirror
76.
[0088] The resonator for the resonator radiation field need not,
however, be automatically designed, as illustrated in FIG. 6, such
that it comprises all the solid-state bodies. It is likewise
conceivable to associate a separate resonator with each solid-state
body and then use the laser radiation fields exiting from the
respective resonators either individually for separate tasks or
superimpose them.
[0089] A fourth embodiment of an inventive laser amplification
system, illustrated merely schematically in FIG. 7, is based on the
first embodiment, wherein the individual solid-state bodies
10.sub.1 to 10.sub.4 are, however, penetrated not only by the first
pumping radiation path with the first pumping branches 38.sub.1,
38.sub.2, 38.sub.3 and 38.sub.4 and, in addition, with the pumping
branches 138.sub.1, 138.sub.2, 138.sub.3 and 138.sub.4 of the
second pumping radiation path but, in addition, a third pumping
radiation path and a fourth pumping radiation path are provided,
wherein the fourth pumping radiation path is formed by additional
optical refocusing means 250.sub.1, 250.sub.2, 250.sub.3 and
250.sub.4, between which the third pumping branches 238.sub.1,
238.sub.2, 238.sub.3 and 238.sub.4 extend. Optical refocusing means
350.sub.1, 350.sub.2, 350.sub.3, 350.sub.4 are also provided for
the fourth pumping radiation path and these image the pumping
branches 338.sub.1, 338.sub.2, 338.sub.3 and 338.sub.4 into one
another. As for the rest, the fourth embodiment is constructed, in
principle, in the same way and operates in the same way as the
first embodiment and so the entire explanations concerning the
first embodiment with respect to the planes, in which the pumping
branches 38, 138, 238 and 338 are located, also apply for the
fourth embodiment.
[0090] The advantage of the fourth embodiment is that the
possibility is created of pumping the respective solid-state body
10.sub.1 to 10.sub.4 even more uniformly with the pumping radiation
field.
* * * * *