EP1920509A1

EP1920509A1 - Laser array

Info

Publication number: EP1920509A1
Application number: EP05783770A
Authority: EP
Inventors: Daniel Bartoschewski; Björn LANGER
Original assignee: Limo Patentverwaltung GmbH and Co KG
Current assignee: Focuslight Germany GmbH
Priority date: 2005-08-19
Filing date: 2005-08-19
Publication date: 2008-05-14
Also published as: JP2009505408A; US7738178B2; KR20080037056A; JP5270342B2; US20080198893A1; WO2007019878A1; CN101273504A; CN101273504B; KR101174322B1

Abstract

The invention relates to a laser array that is suitable for injecting laser light into at least one optical fiber. Said laser array comprises a plurality of laser light sources (100-113) which are placed at a distance from a light incidence surface of the at least one optical fiber, and a diaphragm (700) which is suitable for spatially defining the laser light emitted during operation of the laser light sources (100-113) before the same is injected into the at least one optical fiber. The laser light sources (100-113) encompass at least one group of first laser light sources (100-106) and at least one group of second laser light sources (107-113). The inventive laser array further comprises coupling means that are suitable for coupling the laser light together during operation of the first and second laser light sources (100-106, 107-113) before the laser light enters the at least one optical fiber.

Description

"Laser array"

The present invention relates to a laser arrangement, suitable for coupling laser light into at least one optical fiber, comprising a plurality of laser light sources, which from a

Light entrance surface of the at least one optical fiber are arranged spaced and a diaphragm, which is suitable for a spatial limitation of the laser light emitted during the operation of the laser light sources prior to coupling into the at least one optical fiber.

Laser arrangements of the type mentioned are known in principle from the prior art. For high-power laser diode systems with fiber coupling, laser diode bars or individual laser diodes (so-called single

Emitter) used as radiation sources and arranged in such a way that the distances of the radiation sources are different from the light entry surface of the optical fiber. If the resulting laser light beam before focusing on the light entry surface of the optical fiber with only a single

Aperture is limited, no optimized in terms of the spatial distribution of the laser light result can be achieved in the known laser arrays. Astigmatism errors frequently occur in the known laser arrangements, which can impair the coupling of the laser light into the optical fiber. Another

Disadvantage of the known laser arrangements is that their space requirement is often relatively large due to a large number of optical elements.

This is where the present invention begins. The present invention is based on the object to propose a laser arrangement in which astigmatism errors can be avoided in a simple manner and their space requirement is relatively low.

The solution to this problem provides a laser arrangement of the type mentioned above with the features of the characterizing part of claim 1. The subclaims relate to preferred developments of the invention.

According to the invention, it is proposed that the laser light sources comprise at least one group of first laser light sources and at least one further group of second laser light sources, and in that the laser arrangement comprises coupling means adapted to interconnect the laser light during operation of the first and second laser light sources prior to entry into the at least one optical fiber to pair. By dividing the laser light sources into two groups of first and second laser light sources, which can be operated independently of one another, and by providing the coupling means, a largely astigmatism-free laser arrangement for coupling laser light into an optical fiber can be provided in a simple manner.

In a particularly preferred embodiment, it is proposed that the laser light sources of at least one of the groups of first and second laser light sources are arranged spaced apart from one another in the vertical direction. As a result, the space requirement of the laser arrangement can be reduced. Preferably, both the respectively adjacent first laser light sources and the respectively adjacent second laser light sources are spaced apart in the vertical direction, so that the space requirement of the laser arrangement can be kept relatively small. It can be provided, for example, that the distance of adjacent first and second laser light sources in the vertical direction is at least 1.0 mm. For example, the distance between the adjacent first and second

Laser light sources about 1, 1 mm.

In a particularly preferred embodiment, it is proposed that each of the first and second laser light sources is assigned at least one reflection means, suitable for reflecting the laser light emitted by the first and second laser light sources in the direction of a common main propagation direction of the respective group of first and second laser light sources. In this way, the laser assembly can be made more compact, so that their space requirements can be further reduced.

In an advantageous embodiment, each of the first and laser light sources is assigned at least one fast axis collimation means. This achieves a collimation of the laser light in the fast-axis direction (fast direction), so that the

Beam quality can be improved.

There is a possibility according to a preferred embodiment that the fast-axis collimation means comprise at least one cylindrical lens.

Advantageously, at least one of the groups of first and second laser light sources is assigned at least one slow-axis collimation means. By this measure it is achieved that the light emitted by the laser light sources light also in the slow axis (slow

Direction) can be collimated. In this way, the Beam quality of the laser light before coupling into the optical fiber can be further improved.

There is the possibility that the slow-axis collimation means comprise at least one cylindrical lens.

A preferred embodiment of the invention is characterized in that at least one of the groups of laser light sources is associated with at least one phase delay means. The phase delay means, which is arranged in the beam path of the first and / or second laser light sources, allows a targeted change in the polarization of the laser light emitted by the first and second laser light sources.

For example, the phase delaying means may be a λ / 2

Be delay element. This causes a rotation of the plane of polarization of the laser light by 90 °.

It may be provided in a particularly advantageous embodiment that the coupling means at least one

Polarization coupling device comprise, suitable for coupling the laser light emitted by the group of first laser light sources with the laser light emitted by the group of second laser light sources. In this way, coupling of the laser light emitted from the first and second laser light sources to simple

Be done on the polarization of the laser light.

Preferably, the polarization coupling device is a polarization beam splitter.

In a particularly advantageous embodiment, the coupling means have at least one beam deflecting means, which is suitable deflecting laser light emitted by at least one of the groups of first and second laser light sources in the direction of the polarization coupling device. For example, the main propagation directions of the laser light emitted from the first and second laser light sources may be substantially parallel to each other. In order to couple the laser light in the polarization coupling device with each other, the beam deflecting means may be arranged, for example, for a deflection of the laser light by 90 °.

Preferably, the beam deflecting means comprise at least one mirror element.

In a particularly preferred embodiment, the laser arrangement has at least one spherical lens means, which is arranged in the beam propagation direction behind the diaphragm, suitable for focusing the coupled laser light of the first and second laser light sources onto the light entry surface of the at least one optical fiber. This allows a good focus and thus a relatively low-loss coupling of the

Laser light can be achieved in the optical fiber.

Other features and advantages of the present invention will become apparent from the following description of a preferred embodiment with reference to the accompanying Figure 1, which shows a plan view of a laser assembly according to a preferred embodiment of the present invention in a greatly simplified schematic form.

The laser arrangement, which is suitable for coupling laser light into an optical fiber, comprises a plurality of laser light sources 1 00 - 1 13, which are spaced from a light entry surface of an optical fiber, which is not explicitly shown in Fig. 1. In this embodiment, the laser arrangement comprises a total of fourteen laser light sources 100-1. The laser light sources 100-113 are preferably individual semiconductor laser diodes (so-called single emitters) whose

Light exit surfaces, for example, may have a width of about 100 microns and each of which may have a power of about 4 watts. There is according to a variant of the present invention not shown here also the possibility to use laser diode bars as laser light sources.

Each of the laser light sources 100-113 is associated with a respective fast-axis collimation means, which is arranged in front of the approximately 100 μm wide light exit surface of the corresponding laser light source 100-113. To simplify the presentation, the

Laser light sources 100-113 and their respective associated fast axis collimation means are indicated schematically in FIG. 1 as a single component. The fast-axis collimation means may, for example, comprise at least one cylindrical lens and allow a collimation of the light emitted by the laser light sources 100-1

Laser light in the so-called fast axis (fast axis), in order to improve the beam quality in this way. In addition, each of the laser light sources 100-113 is assigned a respective reflection means 200-213, which is arranged at a distance from the corresponding laser light source 100-113 in the beam path of the laser arrangement. Each of the

Reflecting means 200-213 may, for example, comprise at least one mirror element.

It can be seen that in the case of the laser arrangement presented here, the laser light sources 100-113 are grouped into a group of first laser light sources

100 - 106 and in a group of second laser light sources 107 - 1 13 are divided. As already mentioned above, each of the laser light sources 1 00 - 1 13 of the two groups of first and second laser light sources 100 - 106, 107 - 1 13 each one of the reflection means 200 - 206 and 207 - 213 assigned.

The reflection means 200 - 206 are with respect to their associated first laser light sources 100 - 106 in the beam path of the laser array in the manner angeord net and each with respect to a vertical axis extending from the plane rotated such that the first laser light sources 100 - emitted light after reflection at their respective associated reflection means 200 - 206 can propagate substantially in the z direction. The first laser light sources 100 - 106 are also arranged in this embodiment in the vertical direction and thus offset in height to each other. In this case, the first laser light sources 1 00 - 106 can be arranged offset relative to each other, for example, in the vertical direction and thus in height by about 1, 1 mm. Correspondingly, the reflection means 200 - 206 can likewise be arranged offset from each other by approximately 1, 1 mm in the vertical direction. There is alternatively or additionally also the possibility, in particular in the vertical direction different to use dimensioned reflection means 200-206. The mutually offset arrangement of the first laser light sources 100 - 106 means that the laser light emitted by the first laser light sources 100 - 106 in different, spaced-apart reflection planes, each through the

Propagation directions of the incident on the reflection means 200 - 206 and spanned by these laser beams are spanned, can propagate. In this way, a relatively compact design of the laser arrangement can be achieved. The propagation direction of the laser light after the reflection at the

Reflecting means 200 - 206 will be referred to hereinafter as the main propagation direction of the laser light of the group of first laser light sources 1 00 - 106.

Accordingly, the second laser light sources 107 - 1 13 are also arranged offset in height in the vertical direction relative to each other. In this case, adjacent second laser light sources 107-113 can be arranged offset relative to one another, for example, in the vertical direction and thus in height by approximately 1.1 mm. Accordingly, the reflection means 207 - 21 3 can also be arranged offset by about 1, 1 mm in the vertical direction to each other. Alternatively or additionally, it is also possible, in particular in the vertical direction, to use differently dimensioned reflection means 207-213. The height-offset arrangement of the second laser light sources 107-113 means that the laser light emitted by the second laser light sources 107-113 can also propagate in different, spaced-apart reflection planes. The reflection means 207 - 213, which are associated with the second laser light sources 107 - 1 13, are thus arranged in the beam path of the laser array and each rotated about a vertical axis, that the laser light during operation of the second laser light sources 107 - 1 is also substantially in the z-direction, namely substantially parallel to the main propagation direction of the laser light emitted from the first laser light sources 100 - 106 can propagate. This propagation direction is intended below as the main propagation direction of the group of second laser light sources

107 - 1 13 are designated.

In the main propagation direction of the first group of laser light sources 100-106, behind the reflection means 206, which is assigned to the laser light source 106, a first slow axis

Collimating 300 arranged. The first SIow axis collimation means 300 is suitable for collimation of the laser light emitted by the first laser light sources 100 - 106 and reflected by the reflection means 200 - 206 in the main propagation direction in the so-called slow axis (slow axis). to thereby improve the beam quality. By way of example, the first slow-axis collimation means 300 may comprise at least one cylindrical lens.

Accordingly, in the beam path of the laser array in

Main propagation direction of the second group of laser light sources 107 - 1 13 behind the reflection means 213, which is associated with the laser light source 1 13, a second slow-axis Kollimationsmittel 301 arranged for collimating the laser light emitted from the second laser light sources 107 - 1 13 and from the reflecting means 207-213 in the

Main propagation direction is reflected, in the slow-axis direction is suitable. For example, the second slow-axis collimation means 301 may also comprise at least one cylindrical lens. In order to merge the laser light of the two groups of first and second laser light sources 100 - 106, 107 - 1 13 prior to being coupled into the optical fiber, the laser array has coupling means suitable for the first and second laser light sources 100 - 106, 107 - 1 13 laser light coupled before coupling into the light entry surface of the optical fiber with each other.

In this embodiment, the coupling means comprise a polarization coupling device 400, which may be a conventional polarization beam splitter, for example, and a beam deflecting means 500. In addition, a phase retarder 600, which in this embodiment is a λ / 2 retardation element, is provided in the beam path of the second laser light sources 107-113 is. That of the second laser light sources 107

- 1 13 emitted light which propagates after the reflection at the corresponding reflection means 107 - 1 13 in the main propagation direction by the second slow-axis Kollimationsmittel 301, passes through the phase delay means 600 and thereby experiences due to the λ / 2-

Delay element a 90 ° rotation of the polarization direction.

The laser light is then by means of the Strahlablenkmittels 500, which may for example comprise at least one mirror element, by 90 ° in the direction of the polarization coupling device

400 reflected. In the polarization coupling device 400, the laser light of the second laser light sources 107-113 deflected at the beam deflection means 500 is coupled to one another via the polarization with the laser light emitted by the first laser light sources 100- 106. It can be seen that the coupling of the

Laser light in this embodiment takes place both geometrically and via the polarization. Within the Thus, in the polarization coupling direction 400, the laser light emitted from the first laser light sources 100-106 is coupled with the laser light emitted from the second laser light sources 107-113, and then propagates in the z direction through a diaphragm 700 which is in Beam propagation direction behind the

Polarization coupling device 400 is arranged, and then applies to a spherical lens means 800, which images the laser light onto the light entry surface of the optical fiber is not explicitly shown, so that the laser light can be coupled into the optical fiber with high power.

The laser arrangement shown here provides an anastigmatic arrangement of laser light sources 100-11 and, by virtue of the particular configuration, enables the suppression of laser beams hitting the optical fiber at slow angles in the slow axis (slow axis). It can thereby be achieved that the optical fiber is not heated to a tolerable level by laser light incident at too large angles or impinging on a fiber cladding of the optical fiber, and thus may possibly be damaged.

It can be seen that the laser arrangement requires only a single diaphragm 700, which is arranged in the beam propagation direction in front of the spherical lens means 800. With the aid of the laser arrangement shown here, in which the coupling of the laser light takes place both geometrically and via the polarization, a light spot with a diameter of less than about 50 μm half-width can be made available both in the fast and in the slow axis.

The number of lenses used can also be kept relatively low in the embodiment shown here and the total space requirements of the laser assembly can be reduced. The laser arrangement requires in this embodiment, only fourteen fast-axis collimation means and also two slow-axis collimation means 300, 301 and only a single spherical lens means 800, which is used for focusing the

Laser light is suitable for the light entry surface of the optical fiber.

In the embodiment shown here are approximately square relationships in the size of the light spot and in the

Divergence in fast and slow axis achieved, so that a substantially anastigmatic focus of both axes with only a spherical lens means 800 allows. Thus, a laser arrangement for coupling laser light can be made available in an optical fiber, a trial of the

Coupling efficiency in optical fibers with a fiber core diameter of 50 microns to 100 microns with a numerical aperture (NA) of about 0.22 allowed.

Claims

claims:

1 . Laser arrangement suitable for coupling laser light into at least one optical fiber, comprising:

a plurality of laser light sources (100 - 1 13), which from a light entrance surface of the at least one optical

Fiber are arranged spaced apart;

a diaphragm (700), which is suitable for a spatial limitation of the laser light emitted during the operation of the laser light sources (100-113) before being coupled into the at least one optical fiber,

characterized in that the laser light sources (100-113) comprise at least one group of first laser light sources (100-106) and at least one group of second laser light sources (107-113), and in that the laser arrangement comprises coupling means adapted to irradiate the laser light during operation the first and second laser light sources (100-106, 107-113) prior to entry into the at least one optical fiber.

2. Laser arrangement according to claim 1, characterized in that the laser light sources (100 - 1 13) at least one of

Groups of first and second laser light sources (100 - 106, 107 - 1 13) are arranged spaced apart in the vertical direction.

3. A laser arrangement according to claim 2, characterized in that the distance between adjacent first and second

Laser light sources (100 - 106, 107 - 1 13) in the vertical direction is at least 1, 0 mm.

4. Laser arrangement according to one of claims 1 to 3, characterized in that each of the first and second laser light sources (100 - 106, 107 - 1 13) is associated with at least one reflection means (200 - 206, 207 - 213), suitable, from the first and second laser light sources

(100 - 106, 107 - 1 13) emitted laser light in the direction of a common main propagation direction of the respective group of first and second laser light sources (100 - 106, 107 - 1 13) to reflect.

5. Laser arrangement according to one of claims 1 to 4, characterized in that each of the laser light sources (100 - 1 13) is associated with at least one fast-axis collimation.

6. Laser arrangement according to claim 5, characterized in that the fast-axis collimation means comprise at least one cylindrical lens.

7. Laser arrangement according to one of claims 1 to 6, characterized in that at least one of the groups of first and second laser light sources (100 - 106, 107 - 1 13) is assigned at least one slow-axis collimation means (300, 301).

8. Laser arrangement according to claim 7, characterized in that the at least one slow-axis collimation means (300, 301) comprises at least one cylindrical lens.

9. Laser arrangement according to one of claims 1 to 8, characterized in that at least one of the groups of first and second laser light sources (100 - 106, 107 - 1 13) at least one

Phase delay means (500) is assigned.

10. A laser arrangement according to claim 9, characterized in that the at least one phase delay means (500) is a λ / 2-delay element.

1 1. Laser arrangement according to one of claims 1 to 10, characterized in that the coupling means at least one

Polarization coupling means (400) comprise, suitable for coupling the laser light emitted by the group of first laser light sources (100-106) with the laser light emitted by the group of second laser light sources (107-113).

12. Laser arrangement according to claim 1 1, characterized in that the at least one polarization coupling device (400) comprises a polarization beam splitter.

13. Laser arrangement according to one of claims 1 to 12, characterized in that the coupling means comprise at least one beam deflecting means (600) suitable for at least one of the groups of first and second laser light sources (100 - 106, 107 - 1 13) emitted laser light in Direction of the polarization coupling device (400) distract.

14. Laser arrangement according to claim 13, characterized in that the beam deflecting means (600) comprise at least one mirror element

15. Laser arrangement according to one of claims 1 to 14, characterized in that the laser arrangement comprises at least one spherical lens means (800), which in

Beam propagation direction behind the diaphragm (700) is arranged, suitable, the coupled laser light of the first and second laser light sources (100 - 106, 107 - 1 13) on the Focus light input surface of the at least one optical fiber.