Device, laser system and method for combining coherent laser beams
An apparatus for combining a plurality of coherent laser beams includes a splitting device for splitting an input laser beam into the plurality of coherent laser beams, a plurality of phase setting devices for adjusting a respective phase of one of the coherent laser beams, and a beam combining device for combining the coherent laser beams, which emanate from a plurality of grid positions of a grid arrangement, to form at least one combined laser beam. The beam combining device has a microlens arrangement with exactly one microlens array for forming the at least one combined laser beam.
1 . An apparatus for combining a plurality of coherent laser beams, comprising:
a splitting device for splitting an input laser beam into the plurality of coherent laser beams,
a plurality of phase setting devices each for adjusting a respective phase of one of the coherent laser beams, and
a beam combining device for combining the coherent laser beams, which emanate from a plurality of grid positions of a grid arrangement, to form at least one combined laser beam,
wherein the beam combining device has a microlens arrangement with exactly one microlens array, and the exactly one microlens array emits the at least one combined laser beam; and
wherein the plurality of grid positions are arranged in a first direction at a distance of a focal length f ML of the microlens array upstream of the microlens array and having a distance δ X from one another, which is given by
δ x =p xj
where p x denotes a pitch of microlenses of the microlens array in the first direction.
2 . The apparatus as claimed in claim 1 , wherein the plurality of grid positions are arranged in the first direction, with the coherent laser beams and the microlens array satisfying the following condition:
N=p x 2 /(λ L f ML ),
where N denotes a number of the plurality of grid positions arranged in the first direction, p x denotes the pitch of the microlenses of the microlens array in the first direction, λ L denotes a laser wavelength of the input laser beam, and f ML denotes the focal length of the microlens array.
3 . The apparatus as claimed in claim 1 , wherein the apparatus is configured to couple the coherent laser beams that are adjacent in the first direction into the microlens arrangement with a specified angle difference δθ x , for which the following applies:
δθ x =λ L /p x ,
where λ L denotes a laser wavelength of the input laser beam and p x denotes the pitch of the microlenses of the microlens array in the first direction.
4 . The apparatus as claimed in claim 1 , wherein the coherent laser beams have a fill factor FF x in the first direction, the following applying to the fill factor:
FF x <0.4.
5 . The apparatus as claimed in claim 1 , further comprising:
a control device configured to adjust a respective phase of one of the coherent laser beams on the basis of an arrangement of the respective grid position within the grid arrangement in order to combine the coherent laser beams to form at least one laser beam that is diffracted into at least one order of diffraction.
6 . The apparatus as claimed in claim 5 , wherein the control device is configured to adjust a respective fundamental phase of one of the coherent laser beams, in the case of which fundamental phase the beam combining device combines the coherent laser beams to form one laser beam that is diffracted into exactly one order of diffraction.
7 . The apparatus as claimed in claim 6 , wherein the grid positions are arranged in a first direction and wherein the control device is configured, for the purposes of combining the coherent laser beams to form the exactly one combined laser beam that is diffracted into the exactly one order of diffraction B k,x in the first direction, to set the respective fundamental phase δω a of a coherent laser beam at an a th grid position in the first direction which is given by:
δω a =−π/N ( m a +B k,x ) 2
where the following applies:
m
a
=
-
(
N
+
1
)
2
+
a
with a=1, . . . , N, where N denotes a number of the
grid positions arranged in the first direction and where B k,x is an integer or half integer, for which the following applies:
-
(
N
+
1
)
2
≤
B
k
,
x
≤
+
(
N
+
1
)
2
.
8 . The apparatus as claimed in claim 7 , wherein the grid positions in the grid arrangement are additionally arranged in a second direction perpendicular to the first direction and wherein the control device is configured, for the purposes of combining the coherent laser beams to form the exactly one combined laser beam that is diffracted into the exactly one order of diffraction B k,x in the first direction and into exactly one order of diffraction B j,y in the second direction, to set the respective fundamental phase δφ a,b of a coherent laser beam at an a th grid position in the first direction and at a b th grid position in the second direction which is given by:
δφ a =−π/N ( m a +B k,x ) 2 −π/N ( m b +B j,y ) 2
where the following applies:
m
b
=
-
(
M
+
1
)
2
+
b
with b=1, . . . , M, where M is a number of the grid positions arranged in the second direction and where B j,y is an integer or half integer, for which the following applies:
-
(
M
+
1
)
2
≤
B
j
,
y
≤
+
(
M
+
1
)
2
.
9 . The apparatus as claimed in claim 7 , wherein the splitting device is configured as a further microlens arrangement with at least two further microlens arrays, and wherein the control device is configured, for the purposes of combining the coherent laser beams to form the exactly one combined laser beam that is diffracted into the exactly one order of diffraction B k,x in the first direction and preferably diffracted into the exactly one order of diffraction B j,y in the second direction, to set twice as much of the fundamental phases.
10 . The apparatus as claimed in claim 7 , wherein the control device is configured to set the respective phase of one of the coherent laser beams that is composed of the respective fundamental phase and an additional phase.
11 . The apparatus as claimed in claim 10 , wherein the grid positions are arranged in a first direction and wherein the control device is configured, for the purposes of combining the coherent laser beams to form a single combined laser beam that is diffracted into an order of diffraction B k,x in the first direction that differs from the zeroth order of diffraction, to set the respective additional phase Δφ a of a coherent laser beam at an a th grid position in the first direction which is given by:
Δφ a =−(2π/ N )( a −( N+ 1)/2) B k,x ,
where N denotes a number of the grid positions arranged in the first direction and B k,x denotes an integer or half integer, for which the following applies:
-
(
N
+
1
)
2
≤
B
k
,
x
≤
+
(
N
+
1
)
2
.
12 . The apparatus as claimed in claim 11 , wherein the grid positions in the grid arrangement are additionally arranged in a second direction that is perpendicular to the first direction and wherein the control device is configured, for the purposes of combining the coherent laser beams to form a single combined laser beam that is diffracted into the order of diffraction B k,x in the first direction that differs from the zeroth order of diffraction and into an order of diffraction B k,y in the second direction that differs from the zeroth order of diffraction, to set an additional phase Δφ a,b of a coherent laser beam at an a th grid position in the first direction and at a b th grid position in the second direction which is given by:
Δφ a,b =−((2π/ N )( a −( N+ 1)/2) B k,x +(2π/ M )( b −( M+ 1)/2) B k,y ),
where M denotes a number of the grid positions in the second direction and B j,y denotes an integer or half integer, for which the following applies:
-
(
M
+
1
)
2
≤
B
j
,
y
≤
+
(
M
+
1
)
2
.
13 . The apparatus as claimed in claim 6 , wherein the control device is configured to vary the respective phase of one of the coherent laser beams on the basis of an arrangement of the respective grid position within the grid arrangement in order to change an order of diffraction into which the at least one combined laser beam is diffracted.
14 . The apparatus as claimed in claim 13 , wherein the control device is configured to vary the respective additional phase of the coherent laser beams for the purposes of changing a first order of diffraction, into which a first combined laser beam is diffracted, and/or for the purposes of changing a second order of diffraction, into which a second combined laser beam is diffracted.
15 . The apparatus as claimed in claim 13 , wherein the control device is configured to adjust a respective additional phase of the coherent laser beams for the purposes of producing a specified, in particular different power of at least two combined laser beams that are diffracted into different orders of diffraction.
16 . The apparatus as recited in claim 1 , further comprising:
a seed laser source configured to produce a seed laser beam, and direct the seed laser beam as the input laser beam of the splitting device.
17 . A method for combining a plurality of coherent laser beams, in particular by means of an apparatus as claimed in claim 1 , comprising:
input coupling the plurality of coherent laser beams emanating from a plurality of grid positions arranged in a grid arrangement into a microlens arrangement having exactly one microlens array, and combining the coherent laser beams in the microlens arrangement to form at least one combined laser beam.
18 . The method as claimed in claim 17 , further comprising:
adjusting a respective phase of one of the coherent laser beams on the basis of an arrangement of the respective grid position within the grid arrangement in order to combine the coherent laser beams to form the at least one laser beam that is diffracted into at least one order of diffraction.
19 . The method as claimed in claim 18 , further comprising:
varying a respective additional phase of the coherent laser beams for the purposes of changing a first order of diffraction, into which a first combined laser beam is diffracted, and/or for the purposes of changing a second order of diffraction, into which a second combined laser beam is diffracted, proceeding from a respective fundamental phase in the case of which the beam combining device combines the coherent laser beams to form exactly one laser beam that is diffracted into exactly one order of diffraction.
20 . The method as claimed in claim 18 , further comprising:
adjusting a respective additional phase of the coherent laser beams for the purposes of producing a specified, in particular different power of at least two combined laser beams that are diffracted into different orders of diffraction proceeding from a respective fundamental phase, in the case of which the beam combining device combines the coherent laser beams to form exactly one laser beam that is diffracted into exactly one order of diffraction.
21 . An apparatus for combining a plurality of coherent laser beams, comprising:
a splitting device for splitting an input laser beam into the plurality of coherent laser beams,
a plurality of phase setting devices each for adjusting a respective phase of one of the coherent laser beams, and
a beam combining device for combining the coherent laser beams, which emanate from a plurality of grid positions of a grid arrangement, to form at least one combined laser beam,
wherein the beam combining device has a microlens arrangement with exactly one microlens array for forming the at least one combined laser beam,
wherein the plurality of grid positions are arranged in a first direction at a distance of a focal length f ML of the microlens array upstream of the microlens array and having a distance δ x from one another, which is given by
δ x =P x
where p x denotes a pitch of microlenses of the microlens array in the first direction; and
wherein the coherent laser beams have at the grid positions a beam diameter 2ω FML x , which is given by:
2ω fML x =λ L f ML /P x ,
where λ L denotes a laser wavelength of the input laser beam.
22 . An apparatus for combining a plurality of coherent laser beams, comprising:
a splitting device for splitting an input laser beam into the plurality of coherent laser beams,
a plurality of phase setting devices each for adjusting a respective phase of one of the coherent laser beams,
a beam combining device for combining the coherent laser beams, which emanate from a plurality of grid positions of a grid arrangement, to form at least one combined laser beam,
a seed laser source configured to produce a seed laser beam, and direct the seed laser bean as the input laser beam of the splitting device, and
a further apparatus for combining a plurality of further coherent laser beams, comprising:
a further splitting device for splitting the seed laser beam into the plurality of further coherent laser beams,
a plurality of further phase setting devices for adjusting a respective phase of one of the further coherent laser beams, and
a further beam combining device for combining the further coherent laser beams emanating from a plurality of further grid positions of a further grid arrangement, with the further beam combining device comprising a further microlens arrangement having at least one further microlens array, and a further control device which is configured to adjust the respective phase of one of the further coherent laser beams on the basis of an arrangement of the respective further grid position within the further grid arrangement in order to combine the coherent further laser beams to form a laser beam that is diffracted into exactly one order of diffraction, the diffracted laser beam forming the input laser beam of the splitting device of the apparatus,
wherein the beam combining device has a microlens arrangement with exactly one microlens array for forming the at least one combined laser beam.