DE10007123A1 - Optical arrangement for use with laser diode arrangement, has distance between slow axis collimator elements as integral multiple of distance between emitter elements - Google Patents

Abstract

The arrangement has at least one fast axis collimator (6) for collimating the divergent beams of emitter elements (4) in a fast axis and a following slow axis collimator (8) with several collimating elements (9) for collimating the beams, which are already collimated in the fast axis, in the slow axis. The distance (X2) between the slow axis collimator elements is an integral multiple of the distance (X1) between the emitter elements. Independent claims are also included for the following: a laser diode arrangement.

Description

The invention relates to an optical arrangement according to the preamble Claim 1 and to a laser diode assembly according to the preamble Claim 15.

The radiation of a semiconductor diode laser (here also simplifies diode laser) is characterized by a strongly diverging beam, as opposed to other conventional laser beam sources whose laser beam has a diameter of a few millimeters with a small steel divergence in the range of a few mrad while the divergence for a diode laser is greater than 1000 mrad.

It is also known that in diode lasers the divergence angle in the plane perpendicular to the active layer, d. H. in the so-called "fast-axis" is greater than in the Level of the active layer, d. H. in the so-called "slow axis".

To achieve the highest possible laser power, for example, 20-100 watts from a Achieve semiconductor chip, numerous emitters on a so-called ingot summarized. Usually, 10-200 individual emitters or Emitter groups in a row in the plane parallel to the active layer, d. H. in the Slow axis arranged consecutively. The resulting overall beam of a such billet has an opening angle in the plane parallel to the active layer of about 10 ° and a beam diameter of about 10 mm. This results in a Beam quality in this plane, which is many times lower than the beam quality in the plane perpendicular to the active layer.

The occupation density, which is calculated from the quotient of the radiating surface of the Laser barrens results in the total area is currently available Diode laser bars at approx. 3-50%; however, higher occupancy densities only  allow a pulse operation of the laser. For continuous applications are therefore smaller occupancy densities required.

For the highly divergent radiation of a diode laser for laser applications, for example, material processing, medical technology, pumps of solid-state lasers etc., are collimating and focusing in the beam path optical arrangements necessary.

These optical arrangements usually include in particular one Microoptics executed The correction of the divergence in the slow axis then takes place through a subsequent macro-look.

In such an arrangement is usually the laser radiation of the individual Emitter or emitter elements of the laser bar by means of a micro cylindrical lens in the Fast-Axis, d. H. collimated in the axis perpendicular to the plane of the active layer. this Fast-axis collimator has the optical property of a cylindrical lens, which with their axis is parallel to the slow axis, with all emitters of a Diode laser barrens used, for example, a single continuous cylindrical lens is, with a small focal length in the immediate vicinity of the facet of Diode laser bar, d. H. at a distance of only a few 100 mμ from the emitters or of this facet. In the slow axis the original difference angle becomes z. B. up to the focusing optics maintained (DE 196 49 113).

For laser bars with a low occupation density, i. H. with a bigger one mutual distance of the emitter elements then there is the possibility of a Collimation in the slow-axis, by a slow-axis A collimator having a plurality of lens segments acting in the slow axis (eg US 3 396 344, US Pat. DE 199 39 750).

Fast-axis collimation and slow-axis collimation allow the Beam differential in both axial directions basically reduce so far that with  Such an arrangement, the laser radiation with a focusing optic point can be displayed. Are currently customary for the fast-axis collimation and the Slow axis collimation cylindrical lenses with focal lengths of several 100 μ up to a few millimeters.

As slow-axis collimators Arreyförmige lenses are used, the cylindrical lens segments consist, in the direction of the slow axis to each other and whose center distance is equal to the distance that the emitters on the have used laser bars. At high occupancy densities, d. H. in particular then, if the center distances of the individual emitters are smaller than 100 μ, prepares the Producing the slow-axis collimator lens arrays significant problems, and in particular due to the small center distance of the individual Lensensegmente as well as due to the fact that from practical Production reasons, the individual lens segments not directly to each other but between these transitional zones or Transition areas with minimum dimensions remain. These do not own the desired optical effect, so that at reduced center distances of the Lensensegmente the optically unusable part of such a lens array opposite the usable part and thus also the optically unusable portion of Laser beam power compared to the optically usable part increases.

Furthermore, it is in the known optical arrangements or correction optics Also necessary when reducing the center distance of the emitter on the laser ingot Slow-axis collimators whose lens segments have a reduced Have focal length, so that the slow-axis collimator closer to the respective Laser bar must be positioned. This in turn means that the Axis collimator space available is reduced and thus for the fast Axis collimator reduced dimensions and especially a reduced Focal length are necessary. With decreasing focal length for the fast axis collimator But the beam divergence in the fast-axis increases, as does the influence of the so-called "smile effect". From a technical point of view is currently a meaningful  Lower limit for the focal length of the fast axis collimator or the corresponding Lens at about f = 300 μ.

The object of the invention is to remedy these disadvantages of known correction optics and a correction optics or optical arrangement show, which also in a small center distance of the emitter elements optically perfect collimation both in the Fast-Axis, as well as in the Slow-Axis supplies and are manufactured inexpensively can.

To solve this problem is an optical arrangement according to the Claim 1 is formed. A laser diode array is according to Claim 15 is formed.

Further developments of the invention are the subject of the dependent claims.

The invention will be described below with reference to the figures of an embodiment explained in more detail. Show it:

Fig. 1 shows a simplified representation in top view of a laser diode array having a plurality of laser bars (chip) in the plane of this figure (XZ plane) are successively provided in one coordinate direction (X-axis) emitters, as well as one of a fast axis Collimator and a slow-axis collimator formed optical arrangement;

Fig. 2 in a simplified representation and in side view of the laser diode arrangement of Fig. 1;

FIG. 3 shows a view similar to FIG. 1 of the laser diode arrangement of FIG. 1 together with a further optical element in the form of a redirecting prism;

Fig. 4 in a simplified representation and in plan view similar to Figure 1 shows a further embodiment of the laser diode array according to the invention.

FIG. 5 shows the laser diode arrangement of FIG. 4 in side view; FIG.

FIG. 6 is a view similar to FIG. 3 of the laser diode arrangement of FIG. 4; FIG.

Fig. 7 is a view similar to FIG. 2, but with a plurality of stacked laser bars in a stack.

For better understanding and ease of orientation in the figures, X, Y and Z indicate three mutually perpendicular coordinate axes, hereinafter also referred to as X-axis, Y-axis and Z-axis and of which the X-axis and the Z-axis together the plane of drawing (X-Z plane) of Figs. 1, 3, 4 and 6 and the Y-axis and the Z-axis together the plane of drawing (YZ-plane) of Fig. 2, 5 and 7 define.

In FIGS. 1-3, a laser diode array 1 is shown, among other things, applied from a to a cooler 2 (heat sink) diode laser bar 3 consists, is made of a semiconductor or laser chip emitting a plurality of laser light emitters 4, the active with their Layer lie in a common plane, namely in the XZ plane, and which are provided in a direction extending in this plane axial direction, namely in the X-axis (slow axis) successive and spaced from each other on the ingot 3 .

The individual emitters 4 each deliver a laser beam 5 , which is perpendicular to the YZ plane both in the fast axis, ie in the Y axis perpendicular to the XZ plane, and in the slow axis, ie in the X axis Divergence. To correct for this beam divergence, optical correction elements are provided, namely in the beam path following the emitter 4, first a fast axis collimator 6 arranged directly on the laser bar 3 and following this in the beam path (in the direction of the Z axis) a slow axis Collimator 8 . The fast-axis collimator 6 is formed in the illustrated embodiment by a cylindrical lens acting as a lens element 7 , which lies with its longitudinal extent in the X-axis and in the beam direction, ie spaced in the direction of the Z-axis of the emitters 4 such is that these are respectively arranged in the focal point of the fast-axis collimator 6 , that is, the distance is equal to the focal length of the cylindrical lens element 7 .

The laser radiation of the emitter 4 is denoted by 5a after passing through the fast-axis collimator 6 in the figures and, corresponding to FIG. 2, forms a collimated, ie parallel, beam in the fast-axis (Y-axis).

The slow-axis collimator 8 consists of a lens arrangement or a lens Arrey, which is composed of a plurality of cylindrical lens segments 9 , which are arranged in a common plane perpendicular to the beam path, ie in a common XY plane, in the direction of the Slow -Axis, ie in the direction of the X-axis successive and spaced apart and with their parallel axes of curvature respectively in the fast-axis, ie in the Y-axis lying.

In the figures, x ₁ denotes the axial distance (pitch) which the emitters 4 on the bar 3 have in the direction of the X-axis from one another. With x ₂ , the axial distance (pitch) is referred to, the two adjoining lens elements 9 from each other. For the distances x ₁ and x _{2, the} following applies:

V = x ₂ / x ₁ ,

where V is an integer ratio and in the illustrated embodiment Two is. But there are also other integer ratios V possible.

In the laser diode assembly 1 , the distance and the focal length of the slow-axis collimator 8 are chosen so that it is spaced from the bar 3 at a distance of the focal length of the lens segments 9 and the laser beams 5 a of a first group of emitters 4 each fully, but without Irradiation each incident on a lens element 9 , while the laser beams 5 a of a second group of emitters 4 impinge on two lens elements 9 . For this purpose, the width, the lens elements 9 in the direction of the slow axis (X-axis) have the same or approximately equal to the cross section of the beams 5 a in this axis. Furthermore, the slow-axis collimator 8 is oriented in the laser diode array 1 so that the central axis of each laser beam 5 a (in the direction of the Z axis) is coaxially aligned with the corresponding central axis of a lens segment 9 .

It is understood that the fast-axis collimator 8 or its cylindrical lens segments 9 in the direction of the Y-axis have a height which is at least equal, but preferably greater than the corresponding cross section of the laser beams 5 a in this axial direction.

After passing through the fast-axis collimator 8 , three partial beams result, which are designated in FIG. 3 with 5b1, 5b2 and 5b3 and of which the partial beam 5 b1 through the two parallel lines 10 and 11 , the partial beam 5 b2 are bounded by the parallel lines 12 and 13 and the sub-beam 5 b3 by the two parallel lines 14 and 15 . The sub-beams mentioned are also collimated in the slow axis, but run apart in three different directions, ie, the sub-beam 5 b1 continues in the Z-axis, while the sub-beams 5 b2 and 5 b3 each with a positive or negative acute angle include the Z axis. At a sufficiently large distance in the beam path behind the slow-axis collimator 8 , the partial beams 5 b1- 5 b3 are spatially separated from each other. By an arranged there optical redirection element, which is formed in the illustrated embodiment of the Redirection prism 16 , the obliquely outwardly extending laser beams 5 b2 and 5 b3 are deflected so that after passing through this prism 16 three parallel beams 5 c1 , 5 c2 and 5 c3, which can then be imaged, for example, by another optical arrangement for use in one point.

The described laser diode arrangement 1 has a number of advantages, namely, inter alia:

The lens segments 9 of the slow axis collimator 8 can have a relatively large focal length, so that this collimator can be arranged at a relatively large distance from the ingot 3 and in particular also causes no problems, the fast axis collimator 6 with sufficiently large focal length and with the required space of about 500-100 μ between the ingot 3 and the slow-axis collimator 8 to order.

The slow-axis collimator 8 can be produced with lens spacings x ₂ which lie in the range of <100 μ, which considerably simplifies the production of the slow-axis collimator 8 and moreover also the usable surface of this collimator or of the cylinder lens segments 9 formed lens Arreys significantly improved. It should be noted that the transition regions between the individual segments 9 in particular have certain minimum dimensions due to production, so that at larger lens spacings x ₂ and resulting larger lens surfaces inevitably increases the ratio between usable lens surface and the transition areas.

The prism 16 is, for example, disposed behind the slow-axis collimator 8, where already a complete physical separation of the beams 5 5 b1 b3 is present at a distance of about 50-200 mm. As shown in FIG. 2, an emitter 4 of the second group takes place in the direction of the X-axis in each case on an emitter 4 of the first group.

In the case of the laser diode arrangement 1 , it was assumed that the slow-axis collimator 8 or its lens segments 9 are positioned such that each emitter 4 of the first group is coaxially opposed by a lens segment 9 . In an embodiment of the laser diode arrangement in this form, depending on the ratio V, the number of partial beams 5 b apparent from the table below results.

Ratio V = x ₂ / x ₁ Number of partial beams 1 1 2 3 3 5 4 7

Figs. 4-6 show as another possible embodiment, a laser diode assembly 1 a, in which the slow-axis collimator 8 is aligned so that each laser segment 5 a of two adjacent emitters 4 impinge on each lens segment 9 and each of these laser beams 5 a there in the direction of the X-axis has a Querschnitsabmessung, which corresponds to half the cross section of a cylindrical lens segment 9 in this axis. Also in this embodiment, the axial distance x _{2 of} the lens elements 9 is twice as large as the distance x _{1 of} the emitter 4 on the ingot. 3

As shown in particular in FIG. 6, in this embodiment, after passing through the slow-axis collimator 8, only the two partial beams 5 b 2 and 5 b 3 are formed , which in each case enclose an angle with the z-axis and through the lines 12 and 13 or 14 and 15 are limited. With the prism 16 a, which in this embodiment, the number of partial beams 5 b2 and b3 5 correspondingly only two prism sections, the partial beams are 5 b2 and 5 b3 in the parallel partial beams 5 c2 and 5 c3 transformed.

The provided in the laser diode array 1 a staggered arrangement of the slow axis collimator 8 may be particularly useful if in the plane of this collimator there is an intensity distribution of the total formed by the laser beams 5 a total radiation having certain maxima and minima. In these cases, it is then useful to position the slow-axis collimator 8 so that the minima are respectively aligned with the position of the transitions between the Lisen segments 9 .

It has been assumed above that only one laser bar 3 with a plurality of emitters is provided. In principle, it is also possible to provide a plurality of laser bars 3 in a plurality of mutually offset in the direction of the Y-axis parallel planes. A laser diode arrangement 1 b of this type is shown in FIG. 7. As shown, a separate fast-axis collimator 6 is provided for each ingot 3 or the emitters 4 there, and thus for each plane, and a separate slow-axis collimator 8 following this, while the redirectional optics, which in turn are provided by a Prism 16 or 16 a is formed, is provided for all levels in common. In principle, it is also possible to combine the slow-axis collimators of all levels into a single optical component.

The invention has been described above by means of exemplary embodiments. It is understood that numerous changes and modifications are possible without thereby departing from the inventive idea underlying the invention. For example, it is also possible to change the ratio V between the distances x ₂ and x ₁ , wherein the number of sub-beams after the slow-axis collimator changes as a function of this ratio.

It has also been assumed above that the fast-axis collimator 6 is formed by a continuous or monolithic cylindrical lens 7 . Basically, it is also possible to use 7 individual lens segments instead of druchgehenden cylindrical lens, which then allow an individual adjustment of the laser beams 5 a of the individual emitter 4 or for several emitters 4 together, for example, to remedy the so-called "smile effect", the then occurs when the individual emitters 4 of the corresponding ingot 3 are not arranged exactly in a common plane plane.

LIST OF REFERENCE NUMBERS

1

.

1

a,

1

c laser diode arrangement

2

heat sink

3

Laser bar or chip

4

emitter

5

.

5

a laser beam

5

b

5

c partial beam

6

Fast axis collimator

7

cylindrical lens

8th

Slow-axis collimator

9

lens segment

10-15

line

16

.

16

a redirection prism

Claims (14)

An optical arrangement for a laser diode array having at least one row of laser emitting emitter elements ( 4 ) arranged in this row in an active layer in a common plane (XZ plane) perpendicular to its fast axis (Y axis), namely in the direction of their slow axis (X-axis) follow one another and at a first distance (x ₁ ) spaced apart, with at least one in the beam direction to the emitter elements ( 4 ) following fast-axis collimator ( 6 ), the collimation causes the divergent laser beams ( 5 ) of the emitter elements ( 4 ) in the fast axis (Y-axis), and with a following in the beam direction to the fast-axis collimator ( 6 ) Slow-axis Kollilmator ( 8 ) with multiple collimator elements ( 9 ), which are offset from one another in the slow axis (X-axis) and at a second distance (x ₂ ) from each other and a collimation of the collimated in the fast-axis beams ( 5 a) in the slow-axis Cause Axis, d adurch characterized in that the second distance (x ₂ ) by an integer multiple is greater than the first distance (x ₁ ). 2. An optical arrangement according to claim 1, characterized by a in the beam path to the slow-axis collimator ( 8 ) following Redirektionsoptik ( 16 , 16 a) for deflecting the slow-axis collimator ( 8 ) emerging, collimated and in different Divergent sub-beams ( 5 b1- 5 b3) into parallel sub-beams ( 5 c1- 5 c3). 3. An optical arrangement according to claim 1 or 2, characterized in that the Ratio of the center distances is two. 4. An optical arrangement according to claim 1 or 2, characterized in that the Ratio of the center distances is greater than two.   5. Optical arrangement according to one of the preceding claims, characterized in that the Redirektionsoptik ( 16 , 16 a) is a prism arrangement. 6. Optical arrangement according to one of the preceding claims, characterized in that the slow-axis collimator segments are cylindrical lens segments ( 9 ). 7. Optical arrangement according to one of the preceding claims, characterized in that the slow-axis collimator of a monolithic, a plurality of cylindrical lens segments ( 9 ) having lens element is formed. 8. Optical arrangement according to one of the preceding claims, characterized in that the Redirektionsoptik ( 16 , 16 a) is provided in the beam path where the from the slow-axis collimator ( 8 ) exiting partial beams ( 5 b1- 5 b3) already have a spatial distance from each other. 9. An optical arrangement according to one of the preceding claims, characterized in that at least two rows of emitter elements ( 4 ), the (rows) in the fast-axis (Y-axis) offset planes (XZ planes) are provided for the emitter elements ( 4 ) of each level a separate slow-axis collimator is provided. 10. Optical arrangement according to one of the preceding claims, characterized in that a common slow-axis collimator ( 8 ) is provided for the emitter elements ( 4 ) of the at least two planes. 11. Optical arrangement according to one of the preceding claims, characterized in that a separate redirecting optics ( 16 , 16 a) is provided for each level. 12. An optical arrangement according to one of the preceding claims, characterized in that for the at least two levels, a common redirecting optics ( 16 , 16 a) is provided. 13. Optical arrangement according to one of the preceding claims, characterized in that each emitter element is formed by an emitter ( 4 ) or a group of at least two emitters ( 4 ). 14. A laser diode array with at least one row of laser emitting emitters ( 4 ), which are arranged in this row with their active layer in a common plane (XZ plane) perpendicular to their fast axis (Y axis), and with an optical Arrangement according to one of the preceding claims.