EP2359444A1

EP2359444A1 - Laser pump arrangement and laser pump method with beam homogenization

Info

Publication number: EP2359444A1
Application number: EP09744705A
Authority: EP
Inventors: Daniel Kopf; Maximilian Lederer
Original assignee: High Q Technologies GmbH
Current assignee: High Q Laser GmbH
Priority date: 2008-11-10
Filing date: 2009-11-06
Publication date: 2011-08-24
Also published as: US8750344B2; CN102246366B; US20120033704A1; CN102246366A; EP2184818A1; WO2010052308A1

Abstract

In a laser pump arrangement for a laser medium that amplifies a laser beam, comprising at least one laser pump source (1'') with a plurality of emitters for generating partial pumping streams (TPS1", TPS2"), the partial pumping streams (TPS1", TPS2") are led through a coupling optic to a homogenizer (3'') and then are thoroughly mixed in one axis through multiple reflections. In the process, the homogenizer (3") and the laser medium are designed and disposed such that the pump stream exiting the homogenizer (3") is led directly onto or into the laser medium while maintaining divergence in the mixing axis (DA), wherein the partial pumping streams (TPS1", TPS2") are projected, in particular focused, directly onto or into the laser medium in a projection axis (PA) that is perpendicular to the mixing axis (DA).

Description

Laser pumping arrangement and laser pumping method with beam homogenization

The invention relates to a laser pump arrangement for a laser radiation amplifying laser medium according to the preamble of claim 1, a laser system equipped therewith and a laser pumping method for a laser radiation amplifying laser medium according to the preamble of claim 15.

Diode-pumped solid-state lasers are standard laser systems used in a wide variety of applications. Power scaling is done in practice using various techniques. The basic problem is usually that as the volumetric pump power density in the laser medium increases, thermally induced effects, e.g. thermal lenses, depolarizations or voltage fractures, lead to the degradation of the beam parameters or to the destruction of the laser medium. In addition, aberrations of the laser mode occur more frequently when high-performance pumping sources, which are required for power scaling, have only poor homogenization.

Scaling by increasing the approximately round pump cross-section is limited possible, but quickly leads to difficulties in the adjustment of the laser mode.

Therefore, various other approaches are known from the prior art, with which a power scaling is sought, which avoid these negative effects or at least reduce. A much better method of scaling offers z. For example, the concept of the disk laser with round pump recirculated several times into the laser medium, as shown for example in EP 0 632 551. Here, thermal effects are reduced with a direct approach by making the laser medium very thin and the cooling is carried out one-dimensionally in the direction of the thin dimension of the laser medium.

The advantages achieved thereby are that on the one hand a very small increase in temperature due to the proximity of the heat sink results, on the other hand, the transverse gradient via the laser mode remain low, since only negligible heat conduction takes place in this direction.

A continuation of this idea is described in EP 1 629 576. Here, by using a highly elliptically focused pumping arrangement in the disk, an additional thermal advantage is achieved by a two-dimensional heat flow, which results in a lower peak temperature.

Advances in fiber-coupled laser diodes have allowed continuous increase in the brilliance of such beam sources, which can be used to achieve scaling along the length of the laser medium. Especially in connection with laser media with comparatively high

Reinforcing cross sections, such as Nd: Vanadate, are achieved with extremely simple structures very good results. The advances that have been made in crystal growth technology over the last 10-20 years have also had a positive impact here. A consistent continuation This concept finally leads to the fiber laser, which, like the disk laser, enables very high output powers.

Finally, there is another possibility of power scaling in the so-called elliptical or highly elliptical pumps. This is a strong focus, z. B. in the vertical direction, maintained to ensure the necessary small signal amplification. On the other hand, the pumped volume is increased by a widening in the other direction. This ensures that the areal power density does not rise above the value critical for thermal effects. A corresponding approach is known, for example, from EP 1 318 578. Scaling is thus achieved by broadening the line. The geometry of the laser medium which is most suitable for this approach is a rod or "slab", as is also described in EP 1 181 754. Particularly important in this context is a very homogeneous pump distribution along the line, since with inhomogeneities very fast This can be achieved, for example, by guiding the light from a laser bar stack by means of a plurality of lenses firstly through a homogenizer with total internal reflection on two sides as a planar waveguide, the exit surface of which then again over a plurality of Such mixing or mixing reduces the influence of dropping or pump power sources that change in their power, so that a homogeneous or homogenized pump beam follows, which is imaged onto the laser medium as a pumped light spot. Although this approach thus allows mixing of the emissions of different laser diodes in the stack, but is complicated due to the lens systems used in the coupling and decoupling in the homogenizer in construction and adjustment. In addition, corresponding requirements for the space requirement of the laser system result from the downstream optics

Generic laser systems with homogenizer bars of the prior art are thus too complex due to their structure and the components used, adjustment-consuming and / or too large.

Other approaches, such as in Beach, Raymond J.: "Theory and optimization of lens ducts", Applied

Optics, Vol. April 12, 1996, pages 2005-2015 or Honea, Eric C. et al. : "Analysis of an intracavity doubled diode-pumped Q-switched Nd: YAG producing more than 100 W of power at 0.352 μm", Optics Letters, Vol. 23, No. 15, August 1, 1998, pp. 1203-1205 Although omitted on a homogenizer downstream optics, but are not suitable for the described applications thorough mixing in two axes to produce highly elliptical Pumpfleckgeometrien.

An object of the present invention is to provide a more compact or simplified laser pumping arrangement for generating elliptical pump geometries and a laser system using the same, in particular a diode-pumped solid-state laser system. Another object is to provide such a laser system which has improved robustness and reduced adjustment effort.

These objects are achieved by the subject-matters of claims 1 and 15 or the dependent claims, and the solutions are further developed.

The invention relates to a pumping arrangement or a pumping method for laser media, in which the partial beams of a plurality or multiplicity of pumping beam sources are collected, mixed and guided as pumping beam for generating elliptical pump geometries on or into a reinforcing laser medium. The cross section of the elliptical pumped light spot to be achieved is described here by the aspect ratio, in which case ratios of pumped light spot length to width of, for example,> 3: 1, in particular> 15: 1 or even higher, are achieved.

The inventive solution for the homogenized pumping of a laser medium is essentially a space-optimized system, which can be constructed with a minimum number of standard lenses plus a homogenizer. Due to the smaller number of lenses compared to the prior art, space requirements and adjustment costs are reduced.

In detail, the optical imaging of the homogenizer output into the laser medium is dispensed with. Instead, both are placed in the immediate vicinity, for example, positioned at a distance of 100-300 microns, so that the pump light without imaging of an actual pump light spot and with a certain cross section under Divergenzerhaltung, apart from the refraction on flat surfaces, essentially in the laser medium is continued. The Divergenzerhalt thus means that apart from the interactions in the entry or passage in optical components, ie the passage through entrance or exit window, in this respect no beam shaping done by designed for this purpose elements. In this respect, the divergence content corresponds to a beam-forming freedom with regard to the change in the divergence. The pumping light is guided in terms of its divergence jet forming free in the laser medium.

The laser medium is thus functionally an extension of the homogenizer, wherein the homogenizer has jet-forming action and provides at its output a beam with the desired cross-section or beam profile. Compared to arrangements with imaging components, the function of the beam shaping by a downstream lens is thus already effected by the homogenizer and its interaction with a coupling-in optics.

The homogenizer as a planar optical waveguide can have polished or coated or mirrored side surfaces to allow the guidance by total internal reflection. The dimensions of the homogenizer are chosen so that in the direction of mixing the required width of the pumping beam in the laser medium is formed and the mixing is sufficiently complete, that is below a tolerance threshold for deviation from the nominal profile of the homogeneous course. Since most laser systems use a linear sequence of laser diodes in the form of laser bars or rows be done, there is a mixing of conditional by this arrangement and spatially offset sub-beam in one axis. As a result, the influence of the different places of origin is eliminated or pushed below a predetermined threshold.

A prerequisite for the desired mixing is the optimized coupling of the partial beams into the homogenizing element, which is possible by the choice of cylindrical coupling-in lenses suitable in the direction of mixing. Divergence and length of the homogenizer are in a dependency ratio, i. high divergence allows for a short homogenizer, whereas low divergence requires a long homogenizer. The high inlet and outlet angles, which occur at high divergence, and the associated reflection losses can be minimized with suitable layer systems both on the homogenizer and on the laser medium.

In the case of the laser diodes usually used, emitter-side collimation already takes place in the fast-axis. This is refocused by a cylindrical lens arranged after the pumping source. The desired focussing, eg d _y = 100-880 μm, can be easily achieved herewith.

As a result of this arrangement, at the end of the homogenizer and in front of the laser medium, ie at the junction of these two components, a homogeneous radiation field with, however, high divergence in the direction of homogenization arises. The waiver of the homogenizer downstream beam shaping, for example in the form of additional lenses can For example, be supported by a transmission-optimizing coating, with a high transmission must be ensured even at the large angles occurring.

Possibly. For example, the beam guidance of the laser light to be amplified by the laser medium can take place from the opposite side, so that the connection medium-rod for the pump light can be highly transmissive, but reflective for the laser light - e.g. by spectrally selective coating. In addition, this should also be true for the full angular range of divergence, e.g. up to 60 °, permeable, so allow a high transmission for a large angle of incidence range.

This arrangement of the two components causes a continuous beam guidance is achieved by the homogenizer in the laser medium, wherein both components connected to each other, that are in contact with each other, or are positioned at a small distance. This distance is determined by the pumping effect to be achieved in the laser medium, ie the width of the pump beam line. Depending on the properties of the mixed beam in the homogenizer, ie in particular its beam cross section and its beam divergence generated there, then the distance can be selected. In contrast to the use of optics between the homogenizer and the laser medium, the beam is continued directly, so that no further, the beam characteristic changing elements are arranged between the components. This relates in particular to the preservation of the beam divergence present at the outlet of the homogenizer. In this sense, a direct continuation of the beam path without Influence of the beam characteristic from homogenizer to laser medium. This becomes clear in the case of direct contacting with fixing and transmission-optimizing compound of both components, which can be achieved, for example, by kitten or diffusion bonding. Homogenizer and laser medium thus form a continuous planar waveguide, which may be interrupted in some embodiments by a narrow, but the divergence preserving free radiation area.

Due to this direct beam continuation, it may be necessary to perform a divergence compensation in the laser medium, which is possible, for example, by highly polished or coated lateral surfaces of the medium.

Perpendicular to the mixing axis, the partial pump radiation of an emitter is guided either directly and without influencing the divergence or else by means of focusing through the homogenizer, i. this mixes only in one axis, whereas in the other axis no mixing but a direct projection on the laser medium takes place. The combination of high divergence in the mixing axis and low divergence or possibly focusing in the projection axis causes a highly elliptical beam cross section of the pump light.

The pumping arrangement according to the invention and the pumping method according to the invention are described in more detail below with reference to exemplary embodiments shown schematically in the drawing or explained in more detail. Show in detail Fig. IA-C is a schematic representation of a first

Embodiment of the inventive

Pump assembly;

2A-E the schematic representation of a second

Embodiment of the inventive

Pump arrangement with variants of a focus in the projection axis;

3 shows the schematic representation of a third

Embodiment of the inventive

Pump assembly;

4 shows the schematic representation of a fourth embodiment of the inventive pumping arrangement;

5 shows the schematic representation of a fifth embodiment of the inventive

Pump assembly;

6 is a schematic representation of a sixth embodiment of the pumping arrangement according to the invention;

7A-B, the schematic representation of a seventh

Embodiment of the inventive

Pump assembly;

8 shows the schematic representation of an eighth

Embodiment of the inventive

Pump assembly; 9A-D show the representation of a first example of the

Beam passage of the pump arrangement according to the invention;

Fig.lOA-D the representation of a second example of the beam path of the inventive pumping arrangement and

Fig.llA-B is the schematic representation of an eighth embodiment of the inventive

Pump arrangement.

Fig. IA-B shows the schematic representation of a first embodiment of the inventive pumping arrangement, wherein Fig. IA is a top and Fig. IB and Fig. IC each represent a side view for different divergences of the emitted pump radiation.

The pumping arrangement for a laser radiation amplifying laser medium has at least one laser pumping source 1 with a plurality of elements for generating partial pumping beams.

In this case laser diodes are mostly used, which are arranged one above the other or next to each other and their

Laser radiation for pumping the laser medium 4 is used.

The partial beams emitted by this laser pump source 1 are mixed in an optical homogenizer 3 arranged downstream of the laser pump source 1 in a mixing axis DA. This has in this embodiment as a homogenizer bar on a rectangular cross-section, wherein its dimensioning as well as the length of the rod from both the laser pump source 1, eg depend on the number and spacing of the individual emitters, as well as the laser medium 4, for example, its material. In general, the homogenizer 3 will have a narrower side, which purely by way of example effects mixing through multiple reflections on this surface within the rod and in the mixing axis DA, whereas focusing may take place in the wider side. For this purpose, however, other, deviating from a parallelepiped or rod geometries can be used according to the invention, whereby a mixing can be effected by the wider side. To ensure lossless reflections during mixing, the homogenizer may have 3 polished or coated side surfaces. The mixing or mixing is based on the condition caused by the different position of the individual emitter different angles of incidence in the homogenizer 3, wherein the Teilpumpstrahlengänge entangled with their divergence by a variety of reflections and thus mixed.

In addition to the mixing, in a projection axis PA perpendicular to the mixing axis DA, a direct projection of the partial pumping beams generated by the emitters of the laser pump source 1 onto the laser medium 4 takes place, ie no mixing or corresponding mixing of the mixing axis DA takes place in this axis or no influence on the beam divergence or Beam convergence through other components. This projection is shown in dashed lines in FIG. Thus, the emission of the laser pump source 1 in the projection axis PA with the original - or only by a microlens on the emitter influenced divergence by the homogenizer 3 while maintaining the beam divergence is performed directly on the laser medium. For this the sub-pumping beams are guided via a coupling optics 2 in the homogenizer 3, wherein this coupling optics 2 in the illustrated embodiment, purely by way of example via two cylindrical coupling lenses 2A and 2B has, in addition to the projection on or in the laser medium 4, both the collection and coupling of the partial beams in the homogenizer 3 as well as influencing the mixing is possible.

Fig. IC shows an embodiment analogous to Fig. 1B, in which by choosing another, e.g. In this case, a microlens with a comparatively longer focal length on the emitter of the laser pump source 1, a smaller divergence in the projection axis PA is achieved, and thereby the pump leak is performed in the laser medium significantly elliptical.

Homogenizer 3 and laser medium 4 are again designed and arranged such that the pump beam emerging from the homogenizer 3 and composed of the mixed partial pumping beams is also guided directly onto or into the laser medium 4 in the mixing axis DA. By this direct and immediate coupling without further intermediate beam-modifying components, a continuous component of homogenizer 3 and laser medium 4 is optically realized, wherein at the transition point of the homogenizer 3 and laser medium 4 while divergence preservation takes place for mixing axis DA and projection axis PA. With correspondingly shaped laser medium 4, this arrangement resembles a continuous planar waveguide. In this case, divergence-compensating reflections can subsequently ensue in the laser medium 4 or else the pump beam is continued here divergenzerhaltend without further reflection. In the case of reflections in the laser medium 4, this may have polished or coated side surfaces for divergence compensation.

In this first embodiment, for this purpose, both components are arranged so that the homogenizer 3, the laser medium 4 contacted, which according to the invention in addition to the unfixed abutment and a fixed connection by kitten or diffusion bonding is possible. A correspondingly mechanically stable connection also contributes to the robustness of the arrangement and allows the waiver of the adjustment effort required for interposed optics. In addition, the homogeneity of Pumpflecks remains, which in the case of an intermediate optics requires a particularly high quality and costly design of this optics in order to achieve a high quality image despite high divergences. Aberrations or aberrations of this optics could otherwise affect the homogeneity of the pump leak. The homogeneity of the pump leak has a direct influence on the achieved beam quality with high beam power, which represents a decisive parameter for many applications.

Depending on the laser medium 4, the beam profile produced at the output of the homogenizer 3 can already substantially correspond in shape and size to the pump beam profile in the laser medium 4 or, due to the divergence of the radiation, only assume the required cross section there. 2 shows the schematic illustration of a second exemplary embodiment of the pump arrangement according to the invention with variants of a focusing in the projection axis. Compared to FIGS. 1A-C, a fundamentally identical structure and an identical homogenizer 3 are used, different variants of the focusing being shown in FIGS. 2A-B and in FIGS. 2C-D. In the variant of FIGS. 2A-B, the coupling optics 2 'now have two plano-convex coupling lenses 2A' and 2B ', with coupling optics 2' also being designed for focusing in the projection axis. In this structure, there is thus a thorough mixing in the mixing axis with simultaneous focusing in the projection axis perpendicular thereto. In the variant of FIGS. 2C-D, the coupling optics 2 "has two cylindrical coupling lenses 2A" and 2B "in analogy to the exemplary embodiment of FIGS. 1A-C, and additionally a cylindrical lens 2C" acting in the projection axis.

According to the invention, both the beam divergence which does not influence the beam divergence in the projection axis and the focusing approach can be described below

Embodiments are combined, so that usually takes place a representation in only one axis. The person skilled in the art can derive further examples according to the invention for optical imaging systems which are described in the

Mixing axis the appropriate figure in the

Homogenizer produced and at the same time in the

Projection axis a suitable Pumpfleckradius in

Generates laser medium and thus achieved the desired ellipticity of Pumpflecks and pumping intensity.

Also, the coupling optics 2, 2 'or 2i I' I according to the invention wholly or partly in the homogenizer be integrated, for example by the entrance window provided with a curvature or the homogenizer is divided. Specific examples of this are shown schematically in FIGS. 2E and 11A-B, but the principle of integration of further optical functions beyond the pure mixing into the homogenizer is also applicable to other exemplary embodiments according to the invention. However, this can require an increased effort on the component side, whereas a separate coupling optics allows the use of homogenizers with planar surfaces.

In the variant of Fig. 2E, the coupling optics 2 of the first embodiment of Fig. IA-B is used with two cylindrical coupling lenses 2A and 2B, but now the homogenizer is divided into a first homogenizer component 3A and a second homogenizer component 3B Carrier component 3C can be interconnected or mutually fixed. The second homogenizer component 3B is designed so that it also provides a focusing effect in addition to the mixing, but first and second homogenizer components 3A and 3B form a continuous homogenizer.

3 shows the schematic illustration of a third exemplary embodiment of the pumping arrangement according to the invention with a basically identical construction in comparison to FIG. 1A-C or FIG. 2A-E. As in the following figures 4-6 here only the top view, ie the mixing axis is shown, so that both the direct projection without focusing gem. Fig. IA-C or the Projection with focus acc. 2A-E according to the invention can be realized for the projection axis. In this embodiment, the homogenizer 3 and the laser medium 4 do not touch, but are positioned at a slight distance from each other. The corresponding distance from the homogenizer 3 and the laser medium 4 can be selected to be smaller than the smallest diameter of a cross section of the exiting pump beam or smaller than the smallest edge length of the homogenizer 3, in particular, this can be between 100 and 880 .mu.m, for example 300 or 500 .mu.m.

A fourth embodiment of the pumping arrangement according to the invention is shown in FIG. 4, in which the homogenizer 3 and the laser medium 4 are in communication with one another. However, at the contact point between these two components, a transmission-increasing layer 5 is arranged, which was applied to the homogenizer 3 during manufacture in this example. However, such a transmission-enhancing layer 5 is not required in all cases, e.g. can be dispensed with, if the refractive indices of the two materials used for homogenizer 3 and laser medium 4 are close to each other.

If the laser medium 4 is used as a mirror element, for example for beam folding in the resonator or as an end mirror, then the laser radiation to be amplified can be guided from the side opposite the homogenizer 3 into the laser medium 4. In this case, the transmission-increasing layer 5 'can be applied over the entire area of the surface of the laser medium 4 facing the homogenizer 3, wherein these are used as a useful signal Reflective laser radiation reflecting, for the pumping radiation is designed to be transmissive. This can be done for example by a spectrally selective Reflexionbzw. Transmission effect for the different wavelengths of pump and Nutzsignalstrahlung be achieved, so that an optimal coupling of the pump radiation takes place in reflection of the laser radiation to be amplified in the laser medium 4. This case is shown in Fig.5 as a fifth embodiment.

A sixth exemplary embodiment of the pump arrangement according to the invention is finally shown in FIG. 6, in which the features of the transmission-enhancing and spectrally selectively reflecting layer 5 'applied over the entire surface to the laser medium 4 are connected to a spacing of the homogenizer 3.

FIGS. 7A-B schematically show a seventh exemplary embodiment of the pump arrangement according to the invention, again with representation of the projection and mixing axis. In this case, the structure corresponds in principle to the second embodiment. 2A-B with a focus in the projection axis. However, in this exemplary embodiment, the laser medium 4 'and homogenizer 3 are matched to one another such that the laser medium 4' acts as a waveguide in continuation of the homogenizer 3 at least in the mixing axis. In this case - in deviation from the embodiment shown - in the projection axis an adjustment of homogenizer cross section and cross section of the laser medium 4 'take place.

8 shows an eighth embodiment of the inventive pumping arrangement, wherein only the Mixing axis is shown. The structure of the coupling optics 2 '' is similar to the arrangement shown in Figure 2C-D, however, a coating 6 is introduced into the homogenizer 3 '''in this embodiment, which is transparent to the pump radiation and reflective for the radiation of the useful signal 7 , The useful signal 7 is for this purpose laterally coupled into the homogenizer 3 '''and emitted after amplification in a trapezoidal in this embodiment laser medium 4''as a reinforced output beam 1'. This amplifier arrangement can be used, for example, for the external amplification of laser beams or else for the resonator-internal amplification.

The examples shown in FIGS. 9A-D and 10A-D have been created by means of ray-tracing, wherein for reasons of illustration the focus which is likewise possible according to the invention has been intentionally omitted in the non-homogenizing plane. In both examples lenses L31095L1-B and LJ1874L1-B are used as coupling lenses 2A and 2B, the first lens LJ1095L1-B spaced di = 28 mm from the laser pump source 1 'and the second lens LJ1874L1 -B of the first is placed at a distance of d ₂ = 4.5 mm. The distance from the second lens LJ1874L1-B to the homogenizer 3 'is d ₃ = 0.3 mm.

In FIG. 9A-D, two partial pump beams TPS1 'and TPS2' for the center and the one-edge emitters of a laser diode stack of 5 mm width are calculated as the laser pumping source 1 '. The half angle of divergence in the slow axis is 3-4 ° and the homogenizer 3 'is as Quartz glass rod with a length of 70 mm and a width of 3 mm formed in the mixing axis. The inventive pumping method is explained with reference to a first example of the beam path of the pumping arrangement according to the invention. By means of two different emitters of the laser pumping source 1 'which are at a distance from one another, partial pumping beams TPS1' and TPS2 'are generated for pumping the laser medium 4 and guided into the homogenizer 3' by coupling optics consisting of two cylindrical lenses as coupling lenses 2A and 2B, at least one cylindrical one Einkoppellinse is oriented with its longitudinal axis in the direction of the axis of mixing. There, mixing of the partial pump beams TPS1 'and TPS2' takes place in at least one axis by multiple reflections, so that a pump beam for the laser medium 4 is generated from the mixed partial pump beams TPS1 'and TPS2'. For reasons of illustration, only two partial pump beams TPS1 'and TPS2' are shown in this figure. According to the invention, however, the emissions of a larger number of emitters are mixed. When generating the pumping beam for the laser medium, the partial pumping beams TPS1 'and TPS2' are passed directly onto or into the laser medium 4 after thorough mixing. By different divergences in the two axes of the mixed Teilpumpstrahlen TPSl 'and TPS2', for example, an elliptical beam profile of the pump beam is generated. This is effected by the fact that the homogenizer 3 'has a dimensioning, which generates an elliptical beam profile of the exiting pump beam, in particular by the targeted generation or maintenance of different beam divergences in the two axes, depending on the application or laser medium used 4 a complete or only partial mixing in the width of the elliptical beam profile can be done.

As can be seen from FIG. 9B, the pumping beam at the output of the homogenizer 3 'has a high divergence in this axis. The divergence in the other axis can remain unaffected by the homogenizer 3 ', so that an elliptical pumplichtfleck arises. According to the invention, however, a focusing can also take place so that pumping light spots or beam cross sections of the pumping beam can also be adapted to a desired cross section or a beam profile which are more or less elliptical.

Fig. 9C shows the divergence in the mixing axis at the end of the homogenizer 3 'in detail. FIG. 9D explains the coupling-in optical system with the two coupling-in lenses 2A and 2B in an enlarged view.

Fig.l0A-D shows the representation of a second example of the beam path of the inventive pumping arrangement. The laser pumping source 1 "producing the two subpump beams TPS1" and TPS2 "'is a 10 mm wide laser diode stack, which again considers the emissions from the center and the edge emitters. The half angle of divergence in the slow axis is 3-4 ° and the homogenizer 3 "is formed as a quartz glass rod with a length of 160 mm and a width of 7 mm in the mixing axis.

As in the case of the first example shown in FIG. 10B, in this case as well the pumping beam at the outlet of the homogenizer 3 "has a high divergence in the mixing axis DA with low divergence in FIG Projection axis PA, so that an elliptical Pumplichtfleck arises. FIG. 10C shows this divergence of the mixing axis at the end of the homogenizer 3 "in detail. Fig. OD illustrates the coupling optics with the two coupling lenses 2A and 2B in enlargement.

In Fig.llA-B, an eighth embodiment of the pumping arrangement according to the invention is shown schematically, in which a provided in the mixing axis with an opening angle of the homogenizer 3 '' '' is used. Here, the opening angle is adapted to the divergence, wherein also the entrance window has a curved shape, so that a lens effect is achieved. In this embodiment, therefore, a part of the functionality of the coupling optics in the homogenizer 3 '' '' laid. Focusing takes place in the projection axis through a cylindrical lens 2 ", so that the pump leak geometry to be achieved in this axis is generated directly.

It is understood that the illustrated pumping arrangement or pumped laser systems represent only embodiments of many realizable embodiments according to the invention and those skilled in the art alternative embodiments of the pump and laser structure, e.g. using other lens parameters or arrangements, homogenizer types or pumped media, such as B. disk laser, can derive.

Claims

claims

1. Laser pump arrangement for generating elliptical pump geometries for a laser radiation amplifying laser medium (4, 4 ', 4' ') with at least

A laser pumping source (1,1 ', 1' ') with a plurality of emitters for generating partial pumping beams

(TPSl, TPS2, TPSl ', TPSl ", TPS2', TPS2"), in particular laser diodes, for pumping the laser medium (4, 4 ', 4 "), • an optical homogenizer (3, 3', 3 '', 3 '' ', 3' '' ') for mixing the subpump beams (TPSl, TPS2, TPSl', TPSl ", TPS2 ', TPS2") in a mixing axis (DA) by multiple reflections,

A coupling optics (2, 2 ', 2 ") between laser pump source (1,1', 1") and homogenizer

/ Q rir 1 _, 1 i rir rr rrrrr \ characterized in that

- The coupling optics (2, 2 ', 2 ") is designed and arranged so that the sub-pumping beams (TPSL, TPS2, TPSl', TPSl", TPS2 ', TPS2 ") in a for

Durchmischungsachse (DA) vertical projection axis (PA) directly on or in the laser medium (4, 4 ', 4 ") projected, in particular to be focused and

- Homogenizer (3, 3 ', 3' ', 3' '', 3 '' '') and laser medium (4, 4 ', 4 ") are formed and arranged so that from the homogenizer (3, 3' , 3 '', 3 '' ', 3' '' ') exiting the pump beam under Divergenzerhaltung for the mixing axis (DA) directly on or in the laser medium (4, 4', 4 '').

2. Laser pump arrangement for generating elliptical pump geometries for a laser radiation amplifying laser medium (4, 4 ', 4'') with at least A laser pumping source (1,1 ', 1'') with a plurality of emitters for generating partial pumping beams

(TPSl, TPS2, TPSl ', TPSl ", TPS2', TPS2"), in particular laser diodes, for pumping the laser medium (4, 4 ', 4' '), • an optical homogenizer (3, 3', 3 ", 3 "', 3" ") for mixing the subpump beams (TPSl, TPS2, TPSl', TPSl", TPS2 ', TPS2 ") in a mixing axis (DA) by multiple reflections,

• a coupling optics (2, 2 ', 2' ') between the laser pump source (1,1', 1 ") and homogenizer

/ oror orrrrrrr r \ r 3, O, O, O, O; , characterized in that

- Emitter, coupling optics (2, 2 ', 2' ') and homogenizer (3, 3', 3 ", 3" ', 3 "") are designed and arranged so that these in cooperation at the output of the homogenizer (3, 3 ', 3 ", 3"', 3 "") generate a pump beam with the elliptical pump geometry, wherein the sub-pumping beams (TPSl, TPS2, TPSl ', TPSl ", TPS2', TPS2") in a direction perpendicular to the mixing axis (DA) Projection axis (PA) under Divergenzerhaltung for the projection axis (PA) on or in the laser medium (4, 4 ', 4' ') projected, in particular to be focused and

- The pump beam from the homogenizer (3, 3 ', 3 ", 3"', 3 "") exiting Divergenzerhaltung for the mixing axis (DA) directly on or in the laser medium (4, 4 ', 4' ') is performed ,

3. Laser pumping arrangement according to claim 1 or 2, characterized in that the homogenizer (3, 3 ', 3 ", 3"', 3 "") a

Having dimensioning, which generates an elliptical beam profile of the exiting pumping beam, in particular by different beam divergences in the mixing axis (DA) and the projection axis (PA).

4. Laser pumping arrangement according to claim 3, characterized in that the beam profile substantially corresponds in shape and size to the pump beam profile in the laser medium (4, 4 ', 4' ').

5. Laser pumping arrangement according to claim 3 or 4, characterized in that there is a complete mixing in the width of the elliptical beam profile.

6. Laser pumping arrangement according to one of claims 1 to 5, characterized in that the distance from the homogenizer (3,3 ', 3' ', 3' '', 3 '' 'M and

Laser medium (4, 4 ', 4' ') smaller than

- The smallest diameter of a cross section of the exiting pump jet or - The smallest edge length of the homogenizer

(3, 3 ', 3 ", 3"', 3 ""), in particular between 100 and 880μm amounts.

7. Laser pumping arrangement according to one of claims 1 to 5, characterized in that the homogenizer (3,3 ', 3' ', 3' '', 3 '' 'M the laser medium (4, 4', 4 '') contacted , in particular connected to this.

8. Laser pumping arrangement according to one of the preceding

Claims, characterized in that between the homogenizer (3,3 ', 3'',3''', 3 '''M and laser medium (4, 4', 4 '') a transmission-increasing layer (5,5 ') is arranged.

9. Laser pumping arrangement according to claim 8, characterized in that the transmission-increasing layer (5,5 ') is reflective for the laser radiation to be amplified, in particular by a spectrally selective reflection.

10. Laser pumping arrangement according to one of the preceding claims, characterized in that the homogenizer (3, 3 ', 3' ', 3' '', 3 '' '') for generating the mixing of the partial pumping jets

(TPSl, TPS2, TPSl ', TPSl' ', TPS2', TPS2 '') in at least the

Mixing axis (DA) polished or coated

Has side surfaces.

11. Laser pumping arrangement according to one of the preceding

Claims, characterized in that the coupling optics (2, 2 ', 2' ') at least one cylindrical coupling lens (2A, 2B), wherein the longitudinal axis is oriented perpendicular to the mixing axis (DA).

12. Laser pumping arrangement according to claim 11, characterized in that the at least one cylindrical coupling lens (2A, 2B) is designed and arranged such that beam divergences of the partial pump beams (TPS1, TPS2, TPS1 ', TPS1', TPS2 ', TPS2'') in the mixing axis (DA) at least obtained or enlarged, in particular to be maximized.

13. A laser system with a laser medium (4, 4 ', 4' ') in a resonator for amplifying laser radiation and a laser pumping arrangement according to one of claims 1 to 12.

14. A laser system according to claim 13, characterized in that the laser medium (4, 4 ', 4' ') for divergence compensation polished or coated side surfaces.

15. Laser pumping process for generating elliptical

Pump geometries for a laser radiation amplifying laser medium with

Emitting a partial pumping beam (TPSI, TPS2, TPSI ', TPSI ", TPS2', TPS2") for pumping the laser medium (4, 4 ', 4' '),

• a mixing of the partial pumping beams

(TPSl, TPS2, TPSl ', TPSl ", TPS2', TPS2") in a mixing axis (DA) by multiple reflections in a homogenizer (3, 3 ', 3 ", 3"', 3 ""),

• generating a pump beam for the laser medium

(4, 4 ', 4 ") from the mixed Teilpumpstrahlen (TPSl', TPSl", TPS2 ', TPS2 "), characterized in that when generating the pumping beam, the Teilpumpstrahlen (TPSl, TPS2, TPSl', TPSl", TPS2 ' , TPS2 ") - in a to the mixing axis (DA) perpendicular projection axis (PA) directly on or in the laser medium (4, 4 ', 4' ') projected, in particular focused and - after mixing under Divergenzerhaltung in the

Mixing axis (DA) directly on or in the laser medium (4, 4 ', 4 ") are performed.

16. Laser pumping method according to claim 15, characterized in that when generating by different divergences of the mixed Teilpumpstrahlen (TPSl, TPS2, TPSl ', TPSl ", TPS2', TPS2") in the mixing axis (DA) and the projection axis (PA) an elliptical beam profile of the pump beam is generated.