DE102008036572B4 - Device for processing optical pulses - Google Patents

Abstract

Apparatus for processing a light beam (20) containing optical pulses (22), comprising at least one pair of two opposing non-planar mirrors (12, 14; 41, 42; 62, 64; 102, 104), with first means for Introducing the light beam (20) into the space (19) between the mirrors (12, 14; 41, 42; 62, 64; 102, 104) of the at least one pair of opposed mirrors (12, 14; 41, 42; 62, 64 102,104), such that at least one sub-beam (28; 80; 120) of the light beam (20) is repeatedly confronted between the mirrors (12,14; 41,42; 62,64; 102,104) of the at least one pair Mirror (12, 14, 41, 42, 62, 64, 102, 104) is reflected back and forth at at least two different points of the mirrors (12, 14, 41, 42, 62, 64, 102, 104), with the second one Means for discharging at least the sub-beam (24; 80; 120) out of the space (19), and third means for varying the sub-beam (28; 80; 120) between the mirrors (12,14; 41,42; 62 , 64; 10 2, 104), characterized in that the third means comprise means for tilting at least one of the mirrors (62, 64; 102, 104) and at least one further mirror (66, 68; 68a; 106, 108, 110, 112) which is arranged outside the space (19) between the mirrors (12, 14; 41, 42; 62, 64; 102 104, 104) of the at least one pair of opposing mirrors, wherein the sub-beam (28; 80, 120) is in a tilted position of the at least one of the mirrors (62, 64; 62a; 102) of the at least one pair of opposed mirrors (12, 14 41, 42, 62, 64, 102, 104) is additionally reflected by the at least one further mirror (66, 68, 68a, 106, 108, 110, 112) such that the mirrors (62, 64, 62a, 102 , 104) of the at least one pair of opposing mirrors (12, 14; 41, 42; 62, 64; 102, 104) in a first operating position only reflect the partial beam (80; 120) between them and additionally in a second operating position via the at least another mirror (66, 68, 68a, 106, 108, 110, 112).

Description

The invention relates to a device for processing a light beam containing optical pulses, comprising at least one pair of two opposing nonplanatory mirrors, with first means for introducing the light beam into the space between the mirrors of the at least one pair of opposed mirrors such that at least one sub-beam of the light beam is reflected back and forth several times between the mirrors of the at least one pair of opposed mirrors at at least two different points of the mirrors, with second means for discharging at least the sub-beam out of the space, and third means for varying that of the sub-beam between the mirrors traversed route.

A device of the aforementioned type is known from DE 1 281 067 A known.

When layers are melted onto a substrate, for example for melting silicon layers in the production of electronic displays, a laser beam is used which falls onto the layer to be fused as a very narrow line beam. The layer and the laser beam are shifted relative to one another transversely to the line formed by the laser beam, so that the laser beam is guided flat over the substrate, the so-called "panel". A panel typically has a size of 900 × 700 mm and the incident laser beam has a length of 750 mm and a width of 5 to 6 μm. By melting the silicon layer, the previously disordered crystal layer is ordered and thus the electron mobility, d. H. the electrical conductivity increased.

In such systems usually pulsed excimer lasers are used. However, excimer lasers only have a very short pulse duration. It is therefore known to use pulse extenders, so-called pulse stretcher, which consist of a delay line and a beam splitter. The pulsed laser beam is split into two partial beams in the beam splitter. One partial beam is fed directly to the output and the other partial beam only after passing through the delay line. The delay of the delay line is usually dimensioned so that the pulse of the second sub-beam hangs at the output directly to the pulse of the first sub-beam. The delay path can be formed as a pair of mirrors or more, wherein the light beam having the optical pulses folded, that is, repeatedly reflected back and forth between the mirrors of the pairs.

In addition, it is also known to realize pure delay arrangements for optical pulses in a similar manner, in that instead of a beam splitter, a deflection mirror is used, which sends the entire incoming laser beam onto the delay path.

From the US 2004/0136417 A1 For example, a pulse stretcher of the type described above is known. It consists essentially of the already mentioned beam splitter and the delay path, which is constructed as a resonator with four mirrors. The four mirrors face each other in pairs and symmetrically. As a result, the second partial beam passes through the resonator over a distance which is approximately equal to twelve times the distance between the mirrors of the pairs.

Disadvantage of this known device is that the delay is fixed.

The US 2007/0237192 A1 discloses a confocal pulse stretcher. This has two pairs of concave mirrors, between which a partial beam is repeatedly reflected back and forth. At least one of the mirrors may be slightly adjusted in the radial direction to compensate for inaccuracies in the radius of curvature of that mirror.

In the US 5 148 318 A Another pulse stretcher is described, which consists of four plan mirrors. Two of these mirrors can be tilted between two operating positions. In the first operating position, a partial beam is guided over all four mirrors, in the second operating position only over three mirrors. The partial beam only touches the mirrors once.

When from the aforementioned DE 1 281 067 A known device, a pair of concave mirrors is used. The mirrors face each other on a common axis of symmetry. The light beam is introduced off-axis through an aperture in one of the mirrors into the space between the mirrors. It is then reflected several times obliquely between the mirrors, wherein the points of incidence of the light beam are arranged on the mirrors along an ellipse. The light beam then leaves the room through an opening in the other mirror. The shape and position of the ellipse, as well as the distance of the impact points along the ellipse from each other, depends on the curvature of the mirrors, their distance from each other and the entry position and the inclination of the incoming light beam. In this device, a so-called Störspiegel is also provided. The interference mirror is a small mirror which is disposed at a position along the ellipse near the surface of one of the mirrors and inclined to this surface. As soon as the light beam falls onto the interference mirror, it is deflected and traverses another path with impingement points arranged on another ellipse. As soon as the light beam reaches the interference mirror again, it is deflected again, and This results in another ellipse, etc. The light beam always strikes the same point of the interference mirror. In this way, the total distance of the reflected light beam between the mirrors can be significantly increased and thereby also changed.

This known arrangement has the disadvantage that it is very difficult to handle, because even the smallest adjustments of the interference mirror lead to significant changes in the duration of the light beam. Furthermore, the known arrangement is not suitable for light beams of high energy.

The invention is therefore the object of developing a device of the type mentioned in such a way that these disadvantages are avoided. In particular, a device is to be made available in which it is possible to set the delay of light pulses of high energy easily and reproducibly.

In a device of the type mentioned above, this object is achieved in that the third means comprise a device for tilting at least one of the mirrors and at least one further mirror, which is arranged outside the space between the mirrors of the at least one pair of opposing mirrors, wherein the partial beam is additionally reflected by the at least one further mirror in a tilted position of the at least one of the mirrors of the at least one pair, so that the mirrors of the at least one pair of opposing mirrors in a first operating position only reflect the partial beam between them and in one second operating position in addition to conduct over the at least one other mirror.

The object underlying the invention is completely solved in this way.

The invention makes it possible to adjust by varying the arrangement of the mirror, the distance traveled by the sub-beam path and thus immediately the incoming delay corresponding delay, with relatively large mirrors are pivoted by a certain angle, so that light pulses of high energy in a simple and reliable manner be diverted and delayed in stages differently.

In this case, it is provided that two mirrors in a first operating position at least reflect the partial beam only between them and additionally guide them in a second operating position via at least one further mirror.

This measure has the advantage that an optically easy-to-control design arises.

It is particularly preferred if at least one of the mirrors is pivotable about axes extending perpendicularly to the second partial beam between the two operating positions.

This measure has the advantage that a particularly simple structure arises in which it is only necessary to pivot the one mirror about a particular fixed axis.

On the one hand, the embodiment can be further developed by virtue of the fact that the two mirrors are symmetrically opposite one another in both operating positions and are pivotable about the axis, and that two further mirrors, which are also symmetrically opposite each other, are provided in addition to the two mirrors.

This measure has the advantage that a simple optical arrangement arises in which the ratio of the delays in the two operating positions is preferably 1: 3.

On the other hand, it is possible for the two mirrors to be symmetrical in relation to one another in both operating positions and for one of the mirrors to be pivotable about the axis, and for another mirror which is likewise not pivotable to be provided next to the non-pivotable mirror.

This measure also has the advantage that a simple optical arrangement arises, in which case the ratio of the delays in the two operating positions is 1: 2.

Finally, however, the embodiment can alternatively be further developed in that the two mirrors are symmetrical only in the first operating position, that only one of the two mirrors is pivotable about the axis, and that in addition to the two mirrors four more, also in pairs opposite each other standing mirrors are provided.

This measure has the advantage that a much greater ratio of the delays of, for example, 1: 5 in the two operating positions is possible.

In the context of the present invention, it is preferred if the mirrors are of spherical design.

This measure has the advantage that easy-to-control optical conditions are present.

This is especially true when the distance between opposing mirrors is equal to their radius of curvature.

In a first variant of the invention, the first means are designed as deflection mirrors.

This measure has the advantage that a device for delaying optical pulses is produced.

In a second variant, however, the first means are formed as a beam splitter, wherein a first partial beam from the beam splitter directly to the second means and a second partial beam is passed to the distance between the mirrors and then to the second means in which the partial beams are combined.

This measure has the advantage that a device for extending optical pulses is formed.

Further advantages will be apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

Embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description. Show it:

1 a pulse stretcher with a mirror pair and beam splitter according to the prior art;

2 a pulse stretcher with two pairs of mirrors according to the prior art;

3 a first embodiment of a pulse stretchers invention with two mirror pairs;

4 A second embodiment of a pulse-stretchers invention with a mirror pair and another mirror; and

5 a third embodiment of a pulse stretchers invention with three mirror pairs.

In 1 designated 10 as a whole, an embodiment of a device according to the invention for extending optical pulses, referred to in the art as "pulse stretcher".

The pulse stretcher 10 has a pair of non-planar, preferably spherical mirrors in confocal arrangement, namely a first mirror 12 and a second mirror 14 , on. The mirror 12 and 14 are concave and are mutually relative to a plane of symmetry 13 symmetrically and diametrically opposite at the same distance. With 16 is the center of curvature of the first mirror 12 and with 17 is the center of curvature of the second mirror 14 designated. A connecting line of the centers of curvature 16 . 17 cuts the plane of symmetry 13 in an intersection 15 , The distance of the mirrors 12 . 14 to each other is equal to their radius of curvature.

A beam splitter, for example a partially or semitransparent mirror 18 , is in the room 19 between the mirrors 12 . 14 namely in the plane of symmetry 13 between the mirrors 12 and 14 arranged. One in the plane of symmetry 13 incoming light beam 20 , for example from a pulsed excimer laser (not shown), has the time course of an input pulse 22 , The light beam 20 is in the half-transparent mirror 18 divided.

A first partial beam 28 in the form of a first output pulse 26 intersperses the semipermeable mirror 18 and will be one of them directly 27 indicated output of the Pulse-Stretchers 10 fed. As a result of the division ratio of the semitransparent mirror 18 for example, 50:50 has the first output pulse 26 a reduced, for example half amplitude, but the same pulse length, each compared to the input pulse 22 ,

A second partial beam 28 is from the semi-transparent mirror 18 reflects and first reaches the first mirror 12 , then as a ray 29 diagonally through the intersection 15 on the second mirror 14 , as a ray 30 parallel to the first partial beam 28 back to the first mirror 12 , as a ray 31 again diagonally through the intersection 15 back to the second mirror, and then as a beam 32 colinear to the second partial beam 28 on the half-transparent mirror 18 who leads him to the exit 27 reflected.

The second partial beam 28 appears there as a second output pulse 38 , which also reduced a, for example, half the amplitude and the same pulse duration as the input pulse 22 has and the first part of the beam 24 as outgoing light beam 39 superimposed. The delay T of the second output pulse 38 relative to the first output pulse 26 is preferably such that the second output pulse 38 to the first output pulse 26 connects, so one compared to the input pulse 22 twice the total output pulse. The delay T corresponds to the transit time of the second partial beam over the entire route 28 - 29 - 30 - 31 - 32 ie about four times the distance of the mirrors 12 and 14 from each other.

It is understood that the processes in reality run a little more complex, because the beam 32 not completely on the semipermeable mirror 18 but with the division ratio of the semipermeable mirror 18 partly again like the second partial beam 28 to the first mirror 12 etc. is passed. This has the consequence in practice that the second output pulse 38 has a reduced amplitude and join more "echoes" as smaller and smaller output pulses. For this reason, the reflectivity of the semipermeable mirror 18 greater than 50%, for example set at 60%.

2 shows with 40 a variant of the Pulse Stretchers 10 out 1 , With the pulse stretcher 40 are two pairs of spherical mirrors 41 / 42 and 43 / 44 provided, which are also inclined at the same distance, but each obliquely to the plane of symmetry to each other. With 45 . 46 . 47 and 48 the centers of curvature are the mirrors 41 . 42 . 43 and 44 designated. The connecting lines 46 - 47 and 45 - 48 intersect at a first intersection 49a , and the connecting lines 47 -Focus 43 and 48 -Focus 44 intersect at a second intersection 49b , This results in how 2 in detail shows a course of a second partial beam 50 over rays 51 - 52 - 53 - 54 - 55 - 56 - 57 - 58 - 59 - 60 - 61 - 62 , which alternates over all four mirrors 41 . 42 . 43 and 44 leads up to the beam 62 again to the second partial beam 50 colinear beam is present.

The delay in this pulse stretcher therefore corresponds approximately to twelve times the distance of the mirrors 42 / 44 respectively. 46 / 48 ,

The delay T is on both pulse stretchers 10 and 40 firmly.

In contrast, shows 3 A first embodiment of the invention, in which the delay is adjustable.

A pulse stretcher 60 has similar to the arrangement according to 2 side by side two pairs of non-planar, preferably spherical and concave mirrors 62 / 64 and 66 / 68 on. The first mirror 62 and the second mirror 64 are each one perpendicular to the plane of the 3 extending axis 70 respectively. 72 pivotable between two operating positions, as with double arrows 74 and 76 indicated. The axes of rotation 70 and 72 extend at least approximately through the center of the respective mirror surface. In a first, solidly drawn operating position 62 . 64 The first and second mirrors are in the same position and orientation as the pulse stretcher 10 in 1 , In a second, in 3 dashed line operating position 62 ' . 64 ' however, the first and second mirrors are in the same position and orientation as the pulse stretcher 40 in 2 ,

A first partial beam 79 in turn, through the semi-transparent mirror 18 passed, as already described.

In the first operating position takes a second partial beam 80 therefore a course over rays 80 - 81 - 82 - 83 - 84 and in the second operating position via beams 80 - 85 - 86 - 83 - 87 - 88 - 82 - 89 - 90 - 81 - 91 - 84 , Since in the first operating position, the distance between the mirrors 62 / 64 four times and twelve times in the second operating position, this means a stepwise switching of the delay in the ratio 1: 3.

4 shows a variant of the embodiment of 3 with a pulse stretcher 60a in which in the left mirror pair 62a . 64a only the upper mirror 62a to 62a ' swiveling and the lower mirror 64a is fixed. Instead of the right mirror pair is just a solid, lower mirror 68 available. This is done by switching between the operating positions 62a and 62a ' Switching the delay in the ratio 1: 2 reached.

In 5 a third embodiment of the invention is shown. A pulse stretcher 100 has side by side three pairs of non-planar, preferably spherical mirrors 102 / 104 . 106 / 108 and 110 / 112 on. The first mirror 102 is again about an axis 105 pivotable between two operating positions. The second mirror 104 is as well as the third to sixth mirror 106 to 112 firmly. The third mirror 106 is in contrast to the third mirror 66 out 3 turned counterclockwise and points diagonally to the bottom right. The fourth mirror 128 is compared to the fourth mirror 68 out 3 slightly twisted clockwise. The fifth mirror 110 is arranged parallel to the axis of symmetry.

In the first operating position is the first mirror 102 in the solid line position, and the first pair of mirrors 102 / 104 is like in 1 . 2 and 3 (There also first operating position) arranged. As a result, a course of a second partial beam again results 120 over rays 120 - 121 - 122 - 123 - 124 ie a distance four times the distance of the mirrors.

In the second operating position is the first mirror 102 ' in the dashed line position. The second partial beam now takes its way over rays 120 - 125 - 126 - 127 - 128 - 129 - 130 - 131 - 132 - 121 - 122 - 133 - 134 - 135 - 136 - 137 - 138 - 139 - 140 - 123 - 124 ie a distance twenty times the distance of the mirrors.

Thus, in this embodiment, the ratio of the delays in the two operating positions is 1: 5.

It is understood that the two illustrated embodiments of pulse stretchers 60 and 100 only to be understood as an example.

One can alternatively the pivoting mirror 62 . 64 and 102 and / or move further displayed mirrors. The number of mirrors can also be varied. Furthermore, one can also adjust the distance between the mirrors in stages or continuously, but only for non-confocal systems. Finally, the illustrated examples are limited to planar arrangements, which is naturally also not restrictive, because of course arrangements in three-dimensional space are possible.

LIST OF REFERENCE NUMBERS

10

Pulse Stretcher

12

first mirror

13

plane of symmetry

14

second mirror

15

intersection

16

Center of curvature of 12

17

Center of curvature of 14

18

semi-transparent mirror

19

room

20

incoming light beam (laser)

22

input pulse

24

first partial beam

26

first output pulse

27

output

28

second partial beam

29-32

radiate

38

second output pulse

39

outgoing light beam

40

Pulse Stretcher

41

first mirror

42

second mirror

43

third mirror

44

fourth mirror

45

Center of curvature of 41

46

Center of curvature of 42

47

Center of curvature of 43

48

Center of curvature of 44

49a,

b intersection

50

second partial beam

51-62

radiate

60; 60a

Pulse Stretcher

62, 62 '; 62a, 62a '

first mirror

64, 64 '; 64a

second mirror

66

third mirror

68; 68a

fourth mirror

70

first axis

72

second axis

74

double arrow

76

double arrow

79

first partial beam

80

second partial beam

82-92

radiate

100

Pulse Stretcher

102

first mirror

104

second mirror

105

axis

106

third mirror

108

fourth mirror

110

fifth mirror

112

sixth mirror

120

second partial beam

122-140

radiate

Claims (8)

Device for processing an optical pulse ( 22 ) containing light beam ( 20 ), with at least one pair of two opposing nonplanatory mirrors ( 12 . 14 ; 41 . 42 ; 62 . 64 ; 102 . 104 ), with first means for introducing the light beam ( 20 ) in the room ( 19 ) between the mirrors ( 12 . 14 ; 41 . 42 ; 62 . 64 ; 102 . 104 ) of the at least one Pair of opposing mirrors ( 12 . 14 ; 41 . 42 ; 62 . 64 ; 102 . 104 ), such that at least one sub-beam ( 28 ; 80 ; 120 ) of the light beam ( 20 ) repeatedly between the mirrors ( 12 . 14 ; 41 . 42 ; 62 . 64 ; 102 . 104 ) of the at least one pair of opposing mirrors ( 12 . 14 ; 41 . 42 ; 62 . 64 ; 102 . 104 ) at at least two different points of the mirror ( 12 . 14 ; 41 . 42 ; 62 . 64 ; 102 . 104 ) is reflected back and forth with second means for discharging at least the sub-beam ( 24 ; 80 ; 120 ) out of the room ( 19 ), and third means for varying the partial beam ( 28 ; 80 ; 120 ) between the mirrors ( 12 . 14 ; 41 . 42 ; 62 . 64 ; 102 . 104 ), characterized in that the third means comprise means for tilting at least one of the mirrors ( 62 . 64 ; 102 . 104 ) and at least one further mirror ( 66 . 68 ; 68a ; 106 . 108 . 110 . 112 ) outside the room ( 19 ) between the mirrors ( 12 . 14 ; 41 . 42 ; 62 . 64 ; 102 . 104 ) of the at least one pair of opposing mirrors, the sub-beam ( 28 ; 80 . 120 ) in a tilted position of the at least one of the mirrors ( 62 . 64 ; 62a ; 102 ) of the at least one pair of opposing mirrors ( 12 . 14 ; 41 . 42 ; 62 . 64 ; 102 . 104 ) additionally of the at least one further mirror ( 66 . 68 ; 68a ; 106 . 108 . 110 . 112 ) is reflected so that the mirrors ( 62 . 64 ; 62a ; 102 . 104 ) of the at least one pair of opposing mirrors ( 12 . 14 ; 41 . 42 ; 62 . 64 ; 102 . 104 ) in a first operating position the partial beam ( 80 ; 120 ) reflect only between themselves and in a second operating position additionally via the at least one further mirror ( 66 . 68 ; 68a ; 106 . 108 . 110 . 112 ) conduct. Device according to claim 1, characterized in that at least one of the mirrors ( 62 . 64 ; 62a ; 102 ) about a perpendicular to the partial beam ( 80 ; 120 ) extending axis ( 70 . 72 ; 105 ) is pivotable between the two operating positions, wherein the axis ( 70 . 72 ; 105 ) extends in particular at least approximately through the center of the respective mirror surface. Device according to claim 2, characterized in that the two mirrors ( 62 . 64 ) are symmetrical in both operating positions and about the axes ( 70 . 72 ) are pivotable, and that in addition to the two mirrors ( 62 . 64 ) two further, also symmetrically opposed mirrors ( 66 . 68 ) are provided. Device according to claim 2, characterized in that the two mirrors ( 62a . 64a ) are symmetrical in both operating positions and one of the mirrors ( 62a ) is pivotable about the axis, and that next to the non-pivoting mirror ( 64a ) another, also not pivotable mirror ( 68a ) is provided. Device according to one or more of claims 1 to 4, characterized in that the mirrors ( 62 . 64 . 66 . 68 ; 62a . 64a . 68a ; 102 . 104 . 106 . 108 . 110 . 112 ) are spherically formed. Apparatus according to claim 5, characterized in that the distance of opposing mirror is equal to its radius of curvature. Device according to one or more of claims 1 to 6, characterized in that the first means are designed as deflection mirrors. Device according to one or more of claims 1 to 6, characterized in that the first means as a beam splitter ( 18 ), wherein a first partial beam ( 79 ) from the beam splitter ( 18 ) directly to the second means and a second sub-beam ( 80 ) on the distance between the mirrors ( 62 . 64 . 66 . 68 ; 62a . 64a . 68a ; 102 . 104 . 106 . 108 . 110 . 112 ) and then to the second means, in which the sub-beams ( 79 . 80 ).

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