WO2006032535A1

WO2006032535A1 - Laser resonator

Info

Publication number: WO2006032535A1
Application number: PCT/EP2005/010375
Authority: WO
Inventors: Alexander Büttner; Uwe Detlef Zeitner
Original assignee: Fraunhofer-Gesellschaft
Priority date: 2004-09-23
Filing date: 2005-09-21
Publication date: 2006-03-30
Also published as: DE102004047493B3

Abstract

The invention relates to a laser resonator which is defined by two surface-structured end mirrors (1, 2). The inventive laser resonator is characterized in that the two surface-structured end mirrors (1, 2) are mounted on a common support. The laser resonator also comprises a beam path which is folded by at least one additional mirror (3). The invention also relates to a method for producing a laser resonator of the aforementioned type.

Description

FRAUNHOFER SOCIETY ... E.V. 057PCT 0902

laser resonator

The invention relates to a laser resonator according to the preamble of the main claim and a method for producing such a Läserresonators.

Such laser resonators, which are delimited by two surface-structured end mirrors, are known, for example, from the patents US Pat. Nos. 5,454,004 and 5,745,511. The purpose of the surface-structured end mirrors is to ensure that the laser resonator receives a fundamental mode which results in better utilization of the pumped region of an active medium in the laser resonator compared to conventional laser resonators and better suppression of higher modes to achieve a better beam quality.

As a rule, laser resonators consist of two opposing mirrors. Such a resonator or a corresponding laser has transversal modes of a shape which results from mirror shape and mirror spacing. In conventional resonators mostly spherical and plane mirrors are used. In conventional spherical resonators, for example, so-called Gauss-Laguer or Gauss-Hermitean modes are generated. Which and how many modes oscillate depends on circulating losses of the modes and a gain which results in an active medium of the laser. Typically, a Gaussian fundamental mode has best beam quality and lowest circulation losses, whereas higher modes experience higher circulation losses. Disadvantages of such conventional resonators is that the typically an¬ swinging modes have a limited in the active medium to a region near an optical axis Aus¬ expansion and therefore an energy stored in the active medium can not be completely consumed the can. Furthermore, arise in conventional

Resonators relatively small differences between the circulation losses of the various modes, so vie¬ le modes swing, which brings a deteriorated beam quality with it.

Essential application goals of resonators with surface-structured mirrors which deviate from conventional, for example spherical, resonators are generation by a user of defined output beam profiles, in particular for the purpose of improved utilization of a pumping volume and thus an increased output power, as well an improvement of the beam quality by increasing the circulation losses of higher modes. The use of surface-structured mirrors thus makes intracavity beam shaping possible, for example se targeted generation of a super-Gaussian fundamental mode, which the said publications and the publications cited therein, in particular in connection with solid state lasers, for example Nd: YAG lasers, CC> ₂ lasers and semiconductor lasers has already been extensively studied.

However, the generic laser resonators known in this way are associated with a decisive disadvantage, which also causes the reason that such lasers are not commercially available despite the obvious advantages. The mentioned disadvantage results from a significantly higher accuracy requirement compared to conventional resonators with regard to an adjustment, in particular a relative adjustment of the two surface-structured end mirrors. Associated with this is a disadvantageously high production outlay, which is unavoidable when using a plurality of surface-structured optical elements for the purpose of a targeted beam shaping in the laser resonator according to the prior art. Unlike in conventional resonators, only very low tolerances are permitted in generic laser resonators if the surface-structured end mirrors are purposeful

Beamforming and generation of a specific Grund¬ mode in a suppression of higher modes should meet. Since laser resonators with two surface-structured end mirrors are generally not rotationally symmetrical with respect to an optical axis, the end mirrors, unlike conventional resonators, have to be adjusted relative to a large number of degrees of freedom, namely as a rule with respect to a mirror spacing. a translation in two lateral dimensions, a rotation about the optical axis and a tilt in two dimensions.

Accordingly, it is an object of the invention to develop a corresponding laser resonator which avoids the described disadvantage of the requirements of an extremely complicated adjustment. The invention is also based on the object of proposing a method for producing such a laser resonator.

This object is achieved by a laser resonator with the characterizing features of the main claim in conjunction with the features of the preamble of the main claim and by a method with the features of claim 16. Vorteil¬ advantageous developments and refinements of Er¬ invention result with the Features of Unteran¬ claims.

The embodiments of the laser resonator in such a way that the two surface-structured end mirror thus the same substrate are arranged ange¬ on a common, which is made possible by the fact ^'that the laser resonator has a weite- by at least one ren mirror folded beam path, has several advantages yourself. Because the end mirrors are arranged on the same substrate, they have a fixed orientation relative to one another. In particular, the two end mirrors or surface structures characterizing these end mirrors can be produced in a single production process, as a result of which the relative orientation of the two end mirrors relative to one another can be defined and implemented with extremely high accuracy. A disadvantageous complicated subsequent adjustment of the two end mirrors relative to one another is unnecessary. by. It should be noted that for an adjustment of the at least one further mirror, which is needed to realize the folded beam path, a significantly lower cost is required because such a further mirror usually only three degrees of freedom (distance and Verkip¬ pung in two directions) must be adjusted. Since the at least one further mirror does not have to have a non-trivial surface structure, a translation in the mirror plane and a rotation around a mirror normal are not significant in this case.

Due to the simplified adjustment, it is also possible to realize significantly reduced tolerances in a laser resonator of the type proposed here compared to the prior art. In turn, a desired fundamental mode of the laser resonator can be realized with higher precision, which makes it possible, for example, to achieve a better space utilization of an active medium or pumping volume of a corresponding laser and thus a higher power yield. Due to the easier and thus more precise adjustment, finally, a better suppression of higher (in particular transversal) modes can be achieved, which results in a better jet quality.

A preferred method for producing a laser resonator of the type described accordingly provides that a surface of the substrate is structured in two regions corresponding to the end mirrors in a single production process by applying further layers and / or by removing surface layers. Such a production process can also be multi-level (for example, by a successive removal of several surfaces). chenschichten). The decisive factor is that the two end mirrors are each processed in one working step, that is to say in particular advantageously without the substrate being reacted between surface-structuring measures in the regions of the two end mirrors. It is particularly advantageous to produce the end mirrors by means of laser lithography, which is possible with extremely high accuracy and relatively low expenditure. To protect surface areas which are not to be removed, masks can be used for this purpose. For the surface structuring of the end mirrors it is also possible to resort to all methods described in the aforementioned publications US Pat. No. 5,454,004 A and US Pat. No. 5,745,511, for which purpose reference is made to these documents, which in this regard are described in their entirety in the present specification should apply.

Surface structured in the present document are those mirrors which deviate from simple plane mirrors or spherical mirrors. Preferably, these should be mirrors with a surface structure by means of which the laser resonator receives a desired fundamental mode, preferably at the same time as good as possible suppression of higher modes. Typically, a corresponding surface structure will be characterized by small length scales compared to the mirror dimensions. The desired (transversal) fundamental mode may, for example, be a supergaussian mode with a view to maximizing space utilization in the active medium.

The surface-structured end mirrors can have refractive profiles, ie continuous profiles. Usually one is facing a desired one Fundamental mode calculated mirror profile be refractive. From this profile integer multiples of half the wavelength can be subtracted, resulting in an equivalent, also exact diffractive profile. It is also possible to use end mirrors with diffractive profiles which only approximate a calculated refractive or diffractive mirror profile. A profile of one of the two or both surface-structured end mirrors can thus also be unsteady and consist, for example, of only a finite number of different levels.

In various embodiments of the invention, it may be provided that one of the end mirrors or each end mirror is mirrored on a side facing the resonator, for example gold-plated or coated with another reflecting layer, or that the substrate is at least in an area at least one of the end mirrors is mirrored on a side facing away from the resonator. In the former

In the case, the respective end mirror is given by a reflective, surface-structured region, while the surface-structured region defining the end mirror is transmissive in the latter case, so that a reflection with a passage of light through the substrate except for a back surface the substrate is connected. With a view to the simplest possible production of the final mirror, it is advantageous if the corresponding side of the substrate is mirror-coated all over, for example gold-plated or coated with another reflective material. A targeted local phase change desired in the case of laser resonators can be achieved in the embodiments of the end mirror explained above. The realization of advantageous basic modes usually leads to surface structures with typical Length scales, which are small compared to a diameter of the corresponding end mirror.

A particularly simple and therefore advantageous structure results if the two surface-structured end mirrors are arranged side by side on one side of the substrate. In that case, it may be sufficient if the laser resonator has, in addition to the two end mirrors, exactly one further mirror and a beam path which is simply folded by means of this mirror. In this case, it may be provided that the laser resonator has an optical axis that is slightly inclined relative to a normal of the substrate and / or the further mirror, for example tilted by 0.5 ° and 2 °, whereby an arrangement of the two Endspiegel next to each other in an otherwise largely symmetrical and clear structure is possible.

Alternatively, it would of course also be possible to realize a path of the beam path through, for example, two further mirrors tilted relative to each other. In the ^"case, the two end mirrors could be next to each other placed on a planar substrate and the optical path are chosen so that the Laserre- sonator a folded at two locations, reflect to the terminally each orthogonal to the substrate optical axis has This embodiment would bring. The The advantage is that the surface structures of the two end mirrors could be taken over by a corresponding laser resonator according to the prior art with two end mirrors facing each other, possibly after a simple mirroring.

Depending on the design, the further mirror can be designed as a plane mirror or have a curved, for example spherically curved, surface. In a typical construction with only a single folded beam path, it may be advantageous if the further mirror is convex. Depending on the embodiment, the substrate may also have a flat or curved surface on which the surface-structured end mirrors are arranged. Here it can be advantageous for the surface of the substrate facing the resonator to be concave, so that a desired basic mode can be realized in a simple manner.

Particularly advantageous embodiments of the invention, which require little effort, provide that the further mirror is provided by a surface of an active medium arranged in the laser resonator.

This surface may possibly be mirrored. A simple structure results from this because it is possible to dispense with an additional component.

The laser resonator may have a decoupling region in a region of one of the two end mirrors or also in a region of the further mirror or one of the further mirrors. For this purpose, a mirroring into the corresponding area can be omitted. It is also possible to mirror the corresponding end mirror or further mirror in such a way that incident light is not completely reflected. The decoupling area can then possibly be just as big as the corresponding end mirror or further mirrors. A decoupling by the further mirror or one of the further mirrors may be particularly advantageous, because it generally has no non-trivial surface structure, which can avoid unwanted diffractions or refractions of light. The present invention can be applied to both stable and unstable resonators. Be¬ special advantages brings the invention for unstable resonators with it, where typically two surface-structured end mirror are required to realize a desired fundamental mode.

Under certain circumstances, a particularly good suppression of higher modes can be achieved by the substrate being blackened in an environment of an end mirror, or darkened by a diaphragm or provided with a scattering surface structure. For this purpose, it may be provided that this end mirror is limited to a range within which the fundamental mode of the laser resonator exceeds a defined threshold, for example a threshold of between 0% and 1% of a maximum intensity of the fundamental mode. As a scattering surface structure, for example, a simple grid may be provided, which may be easier to implement than blackening or dimming, but a similar effect is achieved by light incident in the vicinity of the end mirror light from the Strahlen¬ gear is bent out. For the purpose of better realization of a desired fundamental mode and a better suppression of higher modes, it may also be advantageous if at least one further phase structure, diffraction structure and / or aperture is arranged in the beam path of the laser resonator. This may be a simple diaphragm, a lattice-like structure or else an optical element with a pseudorandom, locally fluctuating phase shift. In particular, a better Aus¬ utilization of the pumped area in the active medium of the corresponding laser can be achieved. If the laser resonator is to be used in a laser with longitudinal excitation, it may be advantageous for the pump radiation to be coupled in by the further mirror or one of the further mirrors. Since, unlike the end mirrors, the latter is generally not surface-structured, a diffraction of the pump radiation which is difficult to control is thereby avoided, whereby the pump radiation can be focused better and a spatially optimized An¬ compared to the prior art movement of the active medium becomes possible.

Finally, provision can be made for an additional mirrored surface to be provided on the substrate outside surface-structured regions, that is to say typically outside the end mirrors, which forms an auxiliary resonator together with the at least one further mirror. This auxiliary resonator, which will typically have lower circulation losses than the actual laser resonator, can be used in an advantageous manner for adjusting the laser resonator. This is due to the fact that such an auxiliary resonator typically speaks more easily than the laser resonator delimited by two surface-structured end mirrors. The additional mirrored surface may, for example, be arranged between the two end mirrors on the substrate. In the same way, it would also be conceivable to provide two additional mirrored surfaces for forming an auxiliary resonator, each of which could be arranged next to one of the end mirrors. Advantageously, the additional mirrored surface or each of the additional mirrored surfaces should be dimmable in order to switch off the auxiliary resonator after adjustment of the laser resonator. This can be achieved, for example, by subsequent blackening of the corresponding surfaces. surface.

Exemplary embodiments of the present invention will be explained below with reference to FIGS. 1 to 5.

It shows

1 shows an embodiment of a laser resonator according to the invention as a longitudinal section and for comparison a corresponding laser resonator in unfolded form,

2 shows, in a corresponding representation, three further exemplary embodiments of laser resonators according to the invention,

3 shows a laser resonator according to the invention in a corresponding representation, supplemented by a plan view of a light exit surface and a plan view of two end mirrors of this laser resonator,

Fig. 4 in one of the Fig. 3 corresponding Dar-position another embodiment of the invention and

5 shows a further inventive Laserreso¬ nator with double folded beam path and for comparison a corresponding

Laser resonator in unfolded form.

The laser resonator shown in FIG. 1 a) has two surface-structured end mirrors 1 and 2, which are arranged side by side on one side of a common substrate. In addition, this one has Laser resonator on a further mirror 3 and thus ei¬ NEN by means of its folded beam path. The further mirror 3 is a plane mirror, with the said substrate also being flat.

For comparison, FIG. 1 b) shows a corresponding laser resonator without the further mirror 3 and accordingly with an unfolded beam path, which otherwise has identical optical properties to the resonator shown in FIG. 1 a). It can be seen that the laser resonator has an optical axis inclined relative to a normal of the two end mirrors 1 and 2 by an angle α, whereby a simple folding of the beam path through the further mirror 3 parallel to the end mirrors 1 and 2 in the exemplary embodiment from FIG a) becomes possible. The angle α shown here has a value of between 0.5 ° and 5 °. An overall length of the unfolded resonator drawn in as L is halved in the laser resonator according to the invention from FIG. 1 a).

The further mirror 3 is executed as an additional component in the illustrated resonator according to the invention. In the same way, this further mirror 3 can also be provided by a preferably mirrored surface of an active medium arranged in the laser resonator.

In a region of the end mirror 2 arranged in FIG. 1 a) below the first end mirror 1, this laser resonator has a decoupling region 4, which, as in the following figures, is indicated by an arrow symbolizing an emerging light. The decoupling region 4 is in the present case realized by a not completely reflective coating of the end mirror. In another embodiment of the invention it can be provided that, for the same purpose, a mirroring of the corresponding end mirror 2 in a subregion is omitted. In the same way, the coupling-out region 4 could also be provided by the further mirror 3 or a partial region of the further mirror 3. In the present exemplary embodiment, it is provided that an injection of pump radiation for longitudinal stimulation of the laser resonator is performed by the further mirror 3, which is not structured itself. Alternatively, excitation by one of the end mirrors 1 or 2 or transversely excitation of the laser resonator would also be possible.

In the present case, the surface-structured end mirrors 1 and 2 have diffractive profiles with a discontinuous course and are mirrored on a side facing the resonator (ie, in FIG. 1 a) on the right) by a gold coating. Alternatively, a design of an end mirror 1 or 2 or of both end mirrors 1 and 2 with transmissive surface-structured regions would also be possible, in which case a side of the substrate facing away from the resonator could be mirror-coated by a corresponding coating. The end mirrors 1 and 2 are structured in such a way that the laser resonator, taking into account the optical properties of the optical medium arranged in the laser resonator, maintains a defined and desired transverse mode as a fundamental mode, while higher modes are relatively well suppressed. For this purpose refractive structured end mirrors can be used in the same way. In the embodiment described herein, theoretically calculated refractive However, mirror profiles approximated by diffractive profiles with approximately the same mirror properties, these diffractive profiles were then realized by Laserli¬ thography in a single manufacturing process on a surface of the substrate. In addition to a local removal of surface layers of the substrate, it would also be possible to apply further layers for the purpose of realizing the surface-structured end mirrors 1 and 2.

Other embodiments of the present invention are shown in FIGS. 2 a) to 2 c). Wie¬ recurring features are, as in the dar¬ on following figures, again provided with the same reference numerals.

In the case of the laser resonator shown in FIG. 2 a), between the two surface-structured end mirrors 1 and 2 there is an additional mirrored surface 5 on the substrate, which also carries the end mirrors 1 and 2. This additional mirrored surface 5, together with the substrate opposite the mirror 3 and arranged parallel to this another mirror 3 forms an auxiliary resonator with whose aid the imaged laser resonator can be adjusted. A region of the laser resonator which first oscillates in this case is indicated in FIG. 2 a) by a dashed double arrow. The additional mirrored surface 5, as well as the further mirror 3, designed as a plane mirror. It is provided that the mirrored surface 5 is blackened or covered after an adjustment of the laser resonator so that only the actual resonator formed by the surface-structured end mirrors 1 and 2 and the further mirror 3 is then operated. With regard to the remaining features, the one shown in FIG. formed laser resonator the Aus¬ management example described above.

A similar laser resonator is shown in FIG. 2 b), which differs from the laser resonator described with reference to FIG. 2 a in that the further mirror 3 does not execute as a plane mirror but as a spherically concave curved mirror is. Similar embodiments are conceivable in which ^' the further mirror 3 has a convex curvature.

Another embodiment is shown in FIG. 2 c). In the laser resonator shown there, which is similar to the laser resonator described with reference to FIG. 1 a), the further mirror 3 is again embodied as a plane mirror. For this purpose, the two surface-structured end mirrors 1 and 2 are arranged on a spherically curved, concave surface of the corresponding substrate.

In all of the exemplary embodiments explained so far, it can be provided that the substrate is blackened or provided with a scattering surface structure, such as a lattice structure, in an environment of the end mirror 2 in which a coupling out of laser light takes place. By means of this blackening or diffractive structure, which causes the end mirror 2 to be limited to a region within which the fundamental mode exceeds a defined threshold, for example between 0% and 1% of a maximum intensity, a particularly good threshold is achieved Suppression of higher transverse modes achieved. Additionally or alternatively, in the beam path of the described laser resonators, ie in a region between the end mirrors 1 and 2 and the further mirror 3, further phase structures, diffraction structures and / or apertures can be arranged, by means of which a better utilization of space in the active medium of the laser resonator and a better suppression of higher modes can be realized.

Of course, such phase or diffraction structures and apertures are to be considered in a calculation of the profiles of the end mirrors 1 and 2.

A design example of a laser resonator in a further embodiment of the invention is shown in FIG. This figure shows an unstable Nd: YAG resonator with Gaussian fundamental mode. This resonator results from simple folding of a linear resonator with an optical axis which is inclined relative to a normal of the end mirrors 1 and 2 by an angle of 0.75 °.

Fig. 3 b) illustrates an intensity distribution of the decoupled fundamental mode on a back side of the substrate, which carries the two end mirrors 1 and 2. The two end mirrors 1 and 2 of this La-serresonators themselves are illustrated in Fig. 3 c). There can be seen a decoupling region 4 of the unstable resonator, which is provided by a non-mirrored and even non-structured quadrant in the end mirror 1. The further mirror 3 serving to fold the laser resonator is again designed as a plane mirror in the present case. Also indicated is a thermal lens 6 which results from heating of the laser resonator and an active medium arranged in the laser resonator during operation of the laser resonator. In the present case, this thermal lens 6 has a focal length of 4 m and is taken into account in a calculation of the end mirrors 1 and 2. The imaged Nd: YAG resonator has an emission wavelength of 1064 nm. In FIG. 3 c), surface-structured regions of the end mirrors 1 and 2 can be recognized outside of the decoupling region 4, on which calculated phase distributions are obtained.

5 are interpreted. The illustrated resonator has a

Length L / 2 of 0.1 m and thus corresponds in its optical properties substantially a ent speaking non-folded resonator a length of L = 0.2 m. Is drawn in Fig. 3 c) finally

.0 also a side length 7 of the end mirror 1 and 2, which has an amount of 1.28 mm.

In a manner corresponding to FIG. 3, another embodiment of the invention is shown in FIG

L5 present invention imaged. Again, it is an Nd: YAG resonator with an emission wavelength of 1064 nm. This resonator, like the laser resonator described above with reference to FIG. 3, has two end mirrors 1 and 2 with a diffractive top surface, However, it is designed differently as a stable resonator and has a fundamental mode which reproduces the Greek letter π. This basic mode, which is coupled out in the outcoupling region 4 in the end mirror 2, or its intensity distribution, is illustrated in FIG. 4 b).

In the case of the laser resonator depicted in FIG. 4 a), the further mirror, which is again designed as a plane mirror, has a spacing of L / 2 = 0.125 m from the

30 is again a thermal lens 6, which results from heating of the active medium and has a focal length of 4 m. Between the end mirrors 1 and 2, similar to the laser resonators of FIGS. 2 a)

35 and 2 b), an additional mirrored surface 5 arranged an¬, running flat and highly reflective is cooperating with the further mirror 3 forms a slightly springing auxiliary resonator for adjusting the laser resonator. This additional mirrored surface 5 can also be seen in FIG. 4 c), which is a plan view of the substrate with the two

End mirrors 1 and 2 shows. 4c) also shows a calculated phase distribution of the two surface-structured end mirrors 1 and 2, which have a side length 7 of 3 mm. It is provided that the additional mirrored surface 5 is darkened after an adjustment of the resonator, for example by means of a suitable aperture. The laser resonator explained with reference to FIG. 4 has an optical axis which is inclined by about 1.16 ° relative to a normal of the end mirrors 1 and 2 and of the further mirror 3. In contrast to a corresponding laser resonator with a beam path which is not folded in a conventional manner, the optical fields traveling back and forth in the resonator no longer propagate parallel to a normal of the end mirrors 1 and 2 and / or the further mirror, as in the previously described embodiments 3, but in a direction tilted by said angle in lateral Di¬ direction. The tilting is effected by changing the optical function of the structured mirrors and can be taken into account in the optical design of the resonator.

The oblique propagation of the fields makes it possible to fold the laser resonator, the additional mirror 3 serving as a folding mirror being positioned here at a distance of half a resonator length L / 2 from the substrate. This reduces a geo metric length of the laser to half. This arrangement allows a lithographically accurate positioning of the two surface-structured end mirrors 1 and 2 on a single substrate in a manufacturing process, ie under exactly the same conditions of manufacture. The end mirrors 1 and 2 are positioned in the lateral dimensions (in mirror plane) as well as with respect to a rotation about a mirror normal lithographically accurate (lateral <0.1 microns, relative rotation <0.001 °) zuein¬ other. The folding is ultimately to be expected with a reduction of diffraction losses and an improvement of the resonator behavior.

The principle described can be applied both to stable resonators and to unstable resonators with arbitrary transverse fundamental mode distributions. The end mirrors 1 and 2 do not necessarily have to be designed with diffractive structures (that is, as discontinuous surface profiles), but may also be refractive, ie. be executed as a smooth surface profiles. The principle can furthermore be applied generally to lasers with any active media. The further mirror 3 can be designed according to the statements as a plane mirror or also have a radius of curvature.

For example, in the case of the laser resonator shown in FIG. 4, a region between the two surface-structured end mirrors 1 and 2 is unstructured and designed with an increased mirror reflectivity, so that the additional mirrored surface 5 forms in this region , a slight oscillation of the laser is possible, whereby Ver¬ tilting of the substrate and the further mirror 3 zu¬ can be adjusted. The auxiliary resonator formed by the additional mirrored surface 5 and the further mirror 3 has significantly lower circulating losses than the actual resonator and becomes therefore dimmed as mentioned after an adjustment of the resonator. Outside of the additional mirrored surface 5 and the surface-structured end mirrors 1 and 2, the substrate has a simple diffractive structure, which causes better suppression of higher modes.

A further embodiment of the invention is finally shown in Fig. 5 a). Recurring features are here again provided with the same reference symbols and will not be explained in detail. In contrast to the laser resonators described above, the laser resonator shown here has, in addition to the two end mirrors 1 and 2 arranged on a single substrate, two further mirrors 3 and a beam path folded twice by means of this mirror 3. This results in a particularly simple beam geometry, which makes it possible to use surface structures for the end mirrors 1 and 2 which are known in the same form from a corresponding conventional linear resonator. Such an optically equivalent linear laser resonator with an unfolded beam path is shown for comparison in FIG. 5 b). From the conventional resonator depicted there, the laser resonator according to the invention from FIG. 5 a) results in a simple manner by adding the further mirrors 3, by means of which the beam path is folded at two points by a respective right angle.

Claims

FRAUNHOFER-GESELLSCHAFT ... eV 057PCT 0902Patentansprüche

1. Laser resonator which is delimited by two surface-structured end mirrors (1, 2), characterized in that the two surface-structured end mirrors (1, 2) are arranged on a common substrate, the laser resonator having at least one center of a further mirror (3) has folded beam path.

2. Laser resonator according to claim 1, characterized in that the two surface-structured end mirrors (1, 2) are arranged side by side on one side of the substrate.

3. Laser resonator according to one of claims 1 or 2, characterized in that it has by means of just one further mirror (3) simply gefal¬ ended beam path.

4. Laser resonator according to one of claims 1 to 3, characterized in that the further mirror (3) is a plane mirror or has a curved surface.

5. Laser resonator according to one of claims 1 to 4, characterized in that the substrate has a flat or curved surface on which the surface-structured end mirror (1, 2) are arranged.

6. Laser resonator according to one of claims 1 to 5, characterized in that the further mirror (3) is given by a surface of an active medium arranged in the laser resonator.

7. Laser resonator according to one of claims 1 to 6, characterized in that it comprises a decoupling region (4) in a region of one of the two end mirrors (1, 2) or the further mirror (3).

8. Laser resonator according to one of claims 1 to 7, characterized in that at least one of the end mirrors (1, 2) is mirrored on a side facing the resonator, or the substrate at least in a region at least ei¬ nes the end mirror (1, 2) is mirrored on a side facing away from the Resona¬ gate.

9. Laser resonator according to one of claims 1 to 8, characterized in that the oberflächen¬ structured end mirror (1, 2) have refractive or diffractive profiles.

10. Laser resonator according to one of claims 1 to 9, characterized in that it forms a stable or an unstable resonator.

11. Laser resonator according to one of claims 1 to

10, characterized in that the substrate in an environment of an end mirror (1, 2) is blackened or provided with a scattering Oberflächen¬ structure.

12. Laser resonator according to one of claims 1 to

11, characterized in that at least one further phase structure, diffraction structure and / or aperture is arranged in the beam path.

13. Laser resonator according to one of claims 1 to

12, characterized in that an additional mirrored surface (5) is located on the substrate outside surface-structured areas, which together with the at least one further mirror (3) forms an auxiliary resonator for adjusting the resonator.

14. Laser resonator according to one of claims 1 to

13, characterized in that a coupling of pump radiation through the further Spie¬ gel (3) is provided.

15. Laser resonator according to one of claims 1 to

14, characterized in that the end mirrors (1, 2) have a laser-lithographed surface.

16. A method for producing a laser resonator according to one of claims 1 to 15, characterized ge indicates that a surface of the substrate in two the end mirrors (1, 2) corresponding areas in a single manufacturing process by applying further layers and / or by ablating Surface layers is struktu¬ ration.