WO1997009759A1

WO1997009759A1 - Laser process and device for scaling frequency-doubled lasers

Info

Publication number: WO1997009759A1
Application number: PCT/EP1996/003767
Authority: WO
Inventors: Keming Du; Peter Loosen
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
Priority date: 1995-09-01
Filing date: 1996-08-27
Publication date: 1997-03-13

Abstract

A laser device has at least two individual laser oscillators (2) whose radiation is focused in a beam by means of optical components. The laser device is characterised in that the frequency of the fundamental wave radiation from the oscillators is doubled by a non-linear crystal (10) and in that the radiations from both oscillators are coaxially superimposed by means of an optical dichroic component (for example a standard (9)). Also disclosed is a scaling frequency process by means of said device. The non-linear crystal and the dichroic component can be combined into one element.

Description

"Laser arrangement and method for scaling frequency-doubled lasers"

The present invention relates to a laser arrangement with at least two individual laser oscillators, the laser radiation of the oscillators being bundled by means of optical components. Furthermore, the invention relates to a method for power scaling of frequency-doubled lasers.

The use of laser arrangements and laser beam sources in relation to the most varied of applications requires, on the one hand, a scaling of the laser power and, on the other hand, an adjustment of the frequency in accordance with the specifications.

With regard to the laser scaling of the laser arrangement towards higher powers, it should be noted that a high beam quality is maintained. On the one hand, there is the possibility of performing the laser power by scaling the oscillator volume. A boundary condition that must be considered here is the relationship between the axial dimensions (resonator length) and the

ERSAΓZBLAΓT (RULE 26) radial dimensions which, in order to achieve a high beam quality, have to be in relation so that the Fresnell number of the oscillator does not become significantly greater than 1. If these boundary conditions are not met, the beam quality of high-power lasers is significantly impaired. Another measure to scale the laser beam power is the use of oscillator amplifiers. These amplifiers are used to amplify the radiation from a laser oscillator with low power and high beam quality to a high power. However, this procedure has its limits, in particular in connection with continuously operated lasers. Finally, in order to scale a laser beam source, laser arrays or field arrangements are set up. In such arrays, several laser oscillators are arranged side by side and operated in parallel. The power of the individual laser oscillators adds up to a total laser power of such a laser array. A problem associated with such a laser array is the coherent coupling of the oscillators to one another. In order to bundle the beams of the individual beam sources of the array in a common focusing point, corresponding optical measures for beam guidance must be taken. Furthermore, imaging errors lead to losses when the radiation of the laser oscillators freely propagates, which in turn has an effect due to a low efficiency. In addition, in order to convert the frequency of the laser oscillators and thus to adapt them to the specific fields of application and the specifications, additional measures must be taken which complicate the above-described problem of power scaling of laser arrangements.

Based on the problems described above and the measures known from the prior art, the present invention is based on the object of specifying a laser arrangement and a method with which the power of at least two individual laser oscillators can be scaled and the frequency can be changed, specifically with a simple optical structure while achieving a high beam quality.

REPLACEMENT BLAπ (RULE 26) Starting from a laser arrangement with at least two individual oscillators, this object is achieved in that the fundamental radiation of the respective oscillator is doubled in frequency by a nonlinear crystal and in that the respective radiation is coaxially superimposed by means of an optical, dichroic component is merged. According to the method, a power scaling of frequency-doubling lasers is carried out in that at least two laser oscillators are arranged next to one another and their fundamental wave is doubled in frequency and in that the doubled radiation is brought together coaxially. In order to scale such a laser arrangement in terms of power, essentially two components are required, ie on the one hand a non-linear (s) or more crystal (s), which (s) for frequency doubling of the fundamental wave, that of the individual laseros ¬ zillator is emitted, serves, while the second element in the form of an optical, dichroic components coaxially superimposes the radiation of the respective laser oscillators, so that the powers of the individual laser oscillators are added due to this superimposition. With such a structure, the power can be scaled as desired to higher powers by adding further components in the form of individual laser oscillators to the system. This also applies in particular to continuously operated lasers.

In order to further simplify the arrangement with regard to the number of components required, in a preferred embodiment the dichroic component is designed such that it also takes over the function of the frequency-doubling crystal. For the same reason of reducing the number of individual components and thus simplifying the structure, the laser oscillators are assigned a common, non-linear crystal into which the fundamental radiation of the respective oscillators is radiated.

In particular when the individual laser oscillators are arranged in such a way that the axes of their radiation run parallel to one another, a nonlinear crystal is used which has two parallel surfaces, which are the entrance, exit and / or reflection surfaces for the Form radiation. With such a crystal, the same offsets of the respective neighboring beams are achieved in relation to one another to bring the radiation together, so that a simple geometry results.

To achieve high stability, the individual laser oscillators can be set up as ring resonators. Furthermore, there is the possibility of positioning or dividing the active media in the individual folding sections of the laser oscillators, on the other hand there is the possibility of incorporating the nonlinear crystal and the dichroic component into the individual folding sections. A further, preferred structure can be achieved if the crystal in the ring resonators is assigned a function which deflects the radiation. Here, the crystal should have an entrance surface and a reflection surface, the entrance surface for the fundamental wave (ω) being coated with an anti-reflective coating and for the second harmonic (2ω) being coated with a highly reflective surface, and the reflection surface for the fundamental wave (ω) and the second harmonic (2ω) is highly reflective. With such a coating it is achieved that the respective fundamental waves (ω) reflect on the reflection surface or are deflected to the next element of the ring resonator, while the second harmonic (2ω) reflects on the opposite surfaces and is offset the entry beam emerges from the first surface. The offset is then chosen so that the second harmonic (2ω) is superimposed on the second harmonic (2ω) of the neighboring oscillator.

A coupling-out surface for the second harmonic (2ω) is provided within the entrance surface or the reflection surface of the non-linear crystal in order to couple this radiation component out of the non-linear crystal after combining all the individual oscillators as an output beam.

The structure of the laser arrangement as stated above is preferred in particular with respect to solid-state lasers, moreover for solid-state lasers which are longitudinally pumped by means of diode laser radiation. In connection with solid-state lasers, there is the possibility of the individual To separate the solid media of the individual laser oscillators; However, an embodiment is preferred in which a common solid medium is assigned to the laser oscillators, so that a minimum volume for the active medium is used for such a laser arrangement consisting of solid state lasers. In addition, there is a compact structure with respect to solid-state lasers with ring resonators if the solid-state medium is designed as a prism, with at least two surfaces forming reflection surfaces of the ring resonator. Alternatively, the solid-state medium can be formed as an etaon, one surface having an antireflective coating for the fundamental (ω) and the other surface having a highly reflective coating for the fundamental (co). With this structure, the respective resonator radiation is brought together in the solid body medium, embodied as an etalon, the highly reflective coating for the fundamental wave (ω) of the solid body medium being used in this arrangement at the same time in the context of a ring resonator as a strain element.

If the thermal load on the solid medium becomes too high, especially with regard to scaling the laser to relatively high powers, however, a separate solid medium should be assigned to each laser oscillator.

While preferred structures of the laser arrangement in the form of ring resonators are specified, based on the principle according to the invention, it is also possible to construct a laser arrangement with laser oscillators arranged parallel to one another.

The laser arrangement in the form of individual ring resonators, combining the respective radiation of the individual oscillators by means of an optical, dichroic component in such a way that they are coaxially superimposed, is always preferred when stability and monomode operation are required.

The construction of the laser arrangement in such a way that the laser oscillators each form a linear resonator, the radiation of which is brought together coaxially overlapping by means of an optical, dichroic component Doubling the fundamental radiation of the respective oscillator by means of a non-linear crystal is to be preferred if a flexible design of the laser arrangement and effective cooling have priority.

A preferred embodiment with regard to the linear structure is obtained if the nonlinear crystal, which doubles the fundamental radiation of each oscillator, has a first surface and an opposite second surface, both of which are coated with an anti-reflective coating for the fundamental wave and for second harmonics (2co ) are highly reflective coated, so that the basic radiation (ω) can enter this from both outer surfaces of the nonlinear crystal, while the second harmonic (2co) within the crystal by reflections and to a corresponding coupling-out area, which is for the second Harmonic (2co) is designed to be anti-reflective, is led to decouple the second harmonic (2ω) from the non-linear crystal. It will be understood that the linear crystal is arranged in the beam path of the individual laser oscillators at an angle of incidence of the radiation in such a way that the radiation components are refracted within the crystal and guided in such a way that the doubled radiation (second harmonic (2ω)) the individual laser oscillators are added together and masked out as combined total radiation (2co) from the nonlinear doubling crystal.

Due to the mechanical components required for the construction, and in particular for the adjustment, of the individual laser oscillators, the distances of the radiation from neighboring oscillators on the input side of the dichroic components can be relatively large. In order to keep the dimensions of the dichroic components small, an optical arrangement is advantageous which is inserted into the beam path on the input side of the dichroic components. With this optical arrangement, the distance of the beams of the individual laser oscillators is approximated in the desired manner, preferably via reflection surfaces. For a simple construction, step-like mirror elements are advantageous which deflect the beam at least once and thus bring the beams closer together. In addition, one cannot with such stair-step-like elements by suitable inclination of the reflection surfaces given parallelism of the radiation of the individual laser oscillators can be achieved.

Further preferred measures according to the method are specified in subclaims 33 and 35.

In the drawing shows

1 shows a first embodiment of a laser arrangement according to the invention with three individual laser oscillators with a ring resonator using an etalon for merging or coaxial superimposition of the second harmonic,

2 shows a laser arrangement according to a second embodiment, similar to FIG. 1, the etalon simultaneously taking on the function of a doubler crystal,

FIG. 3 shows a third embodiment with an additional etano compared to FIG. 2, which is pumped by means of a diode laser and acts as an active medium,

FIG. 4 shows a fourth embodiment, modified from FIG. 3, in which a prismatic, active medium is used instead of the etalon-shaped, active medium of FIG. 3,

FIG. 5 shows a fifth embodiment with a square prism as the laser medium,

FIGS. 6 and 7 show a seventh embodiment of a laser arrangement, which by way of example shows two linear resonators with an ethalon-shaped doubler, embodiment 7 having two additional λ / 4 plates on both sides of the active medium compared to the embodiment in FIG. 6,

FIG. 8 shows a further, linear resonator in which the doubler crystal, as shown in FIGS. 6 and 7, is divided into individual segments, the segments being offset from one another, FIG. 9 shows a single segment of the doubler of FIG. 8, the outlet surface being curved, and

Figure 10 schematically shows a structure of a linear oscillator with an optical arrangement for the radiation distance approximation of two adjacent laser oscillators.

FIG. 1 shows an arrangement of three individual laser oscillators 1 with an active medium 2, which are pumped longitudinally by means of diode laser radiation 3, indicated by arrows. The active media are preferably solid bodies which, as indicated in FIG. 1, can be combined to form a common solid body. The individual laser oscillators 1 have a ring resonator with three deflecting mirrors 4, 5 and 6 and a first surface 7 of an etaion 8, which serves as a dichroic component for axially superimposing the radiation from the individual laser oscillators 1. The deflection mirrors 4, 5 and 6 are coated in a highly transparent manner for the fundamental wave (ω) and for the second harmonic (2co). In addition, the deflecting mirror 4 for the pump radiation (fundamental wave (ω)) is highly transparent or antireflective. The etalon 8 has a highly reflective coating on its first surface 7 for the fundamental wave (ω), while the coating on the first surface 7 is highly transparent for the second harmonic (2co). The opposite, second surface 9 of the etalon, parallel to the first surface 7, is provided with a highly reflective coating for the second harmonic. The fundamental waves emitted by the laser media, excited by the diode laser pump radiation, are frequency-doubled within the resonator (second harmonic 2ω) by means of a non-linear doubler crystal 10, which is inserted between the deflecting mirror 6 and the etalon 8 in the beam path. Because of this structure, there are three ring oscillators, each through the beam paths

are given for the reason. The letters a, b, c are assigned to the respective oscillators, while the indices 1, 2, 3, 4 the respective deflecting mirrors 4, 5, 6 and the Etalon 8 are assigned, the details indicating the respective deflection points on the respective elements for the radiation of the respective ring oscillator. The second harmonic (2co) generated in the ring oscillator a ₁ ... a ₃ ... a ₁ in the doubler crystal passes at point a _{4 on the} output side of the doubler crystal 10 via the first surface 7, for the second harmonic ( 2ω) coated with an anti-reflective coating, enters the etalon 8 and follows the path s ^ -b ^ exits the first surface 7 of the etalon 8 and takes the further path b ^ -b _j -b. ,, occurs at the first surface 7 of the etalon 8 back into the etalon, follows the path b _s -c ₄ and then correspondingly further the path c - c ₂ - ^y z ₂ -c ₄ -c _s -d- and is then in place d ₁ decoupled and guided to a deflecting mirror 11, which is highly reflective for the second harmonic (2ω), and deflected at a point cL ^. The second harmonics (2co) generated in the further two ring oscillators 1 run similarly and are decoupled from the etalon 8 at the point d ₁ . In this way, the second harmonics (2co) generated in the various ring oscillators are brought together by means of the etalon and decoupled in such a way that the second harmonics (2ω) coaxially overlap, so that a frequency-doubled output beam 12 is generated, the power of which derives from the individual power of the three ring oscillators additively composed. It can be seen that the power in relation to the second harmonic (2ω) of this laser arrangement can be scaled in a simple manner by the number of ring oscillators. In order to increase the performance, further ring oscillators are added to the arrangement.

As far as the character "ω" is shown in the figures, this indicates the fundamental wave (co), while the character "2ω" indicates the second harmonic (2ω). Furthermore, the reference to surfaces means "HRco" highly reflective for the fundamental wave (ω), "HR2ω" highly reflective for the second harmonic (2ω) and "HTco" highly transmissive or antireflective for the fundamental wave (ω) and "HTωp" highly transmissive for the pump radiation (ω).

As can be seen from FIG. 1, a Faraday rotator 13 for unidirectional operation is in the ring oscillators between the deflecting mirrors 5 and 6 inserted. The laser arrangement of the first embodiment, as shown in FIG. 1, can be simplified in that the etalon denoted by reference number 19 in FIG. 2 consists of a nonlinear material and thus, in addition to bringing the radiation of the individual laser oscillators 1 together serves to double the fundamental radiation (ω) (2ω). In this case, the ring resonators a ^^ - a ^ -a ^ -a ,, b ^ b- _j -b _g -b ^ -b _j -b, and C _j -cjC ₈ -C _j -C ₈ -C _β -c, arranged side by side. The second harmonic (2ω) is generated within the doubler 19 designed as an etalon. The second harmonic (2co) generated within the oscillator a _r ..a ₄ ... a ₁ is guided within the etalon 19 by multiple oscillation to the decoupling point d, which in the second exemplary embodiment shown in FIG Area of the second surface 8 is provided by this surface area 14 for the second harmonic (2ω) is coated with an anti-reflective coating. The same applies to the second harmonics (2co) generated by the two other ring oscillators 1, which are also guided within the doubler etalon 19 to the decoupling point d, so that the respective radiation components of the three laser oscillators 1 coaxially superimpose to form a common output beam 12 become. The power of this output beam 12 is thus additively composed of the individual powers of the laser oscillators 3. As can be seen from the structure as shown in FIG. 2, the second harmonic (2co) does not pass through the active laser medium 2. For this reason, the deflecting mirrors 4, 5 and 6 only have to be highly reflectively coated for the fundamental wave (ω) his.

Insofar as components are designated in FIG. 2 with the corresponding reference numerals and reference signs, which are also used in the first embodiment in FIG. 1, the corresponding statements made with reference to FIG. 1 can be applied to the second embodiment in FIG. 2 be transferred. The same applies to the embodiments explained below with reference to FIGS. 3 to 9.

In the third embodiment, which is shown in FIG. 3, in addition to the frequency-doubling etalon 19, another etalon 22 is used, the

REPLACEMENT SHEET (REGa 26) Etalon 19, the etalon 22 and the deflecting mirrors 5 and 6 fix the resonator. The further etalon 22, which is also the active medium, is emitted by means of diode laser radiation 3 via its outer surface 17, which is (co) highly reflective for the fundamental wave. pumped. Due to the pump radiation, there are three adjacent ring oscillators with the curves shown. The second harmonic (2co) is generated inside the resonator and within the doubler stage 19 and is led to the decoupling point d (surface area 14). Both the doubler etalon 19 and the solid-state etalon 22 each bring the rays together. As shown in FIG. 3, the second harmonic (2ω) up to the decoupling point d only remains within the doubler stage 19. Furthermore, the structure according to the third embodiment, which is shown in FIG. 3, has the advantage that, for example only a solid medium is required.

A fourth embodiment is shown in FIG. 4, which can be regarded as a modification of the third embodiment according to FIG. 3. In contrast to the embodiment in FIG. 3, instead of the etalon-shaped, active medium 22, a laser prism 32 is used as the active medium, which in turn is pumped from the outside by means of three diode lasers, indicated by the radiation arrows 3. A further radiation guiding prism 34, which is transparent to the fundamental radiation (ω), is assigned to the base surface 33 of the laser prism 32, the surface on the right in FIG. 4 of which is assigned a doubler etalon 19, comparable to the doubler etalon of FIG. 3. Both the base surface 33 of the laser prism 32 and the base surface 35 of the radiation guide prism 34 are designed to be (co) antireflective for the fundamental radiation, within the active medium 32 and the radiation guide prism 34, three ring oscillators arise, excited by the diode laser radiation 3 1. In this case, too, the fundamental wave (co) is passed through on the inner, first surface 7 of the doubler stage 19, which is doubled (second harmonic (2ω)), due to the highly reflective coating of the first surface 7 and of the second surface 8 of the etalon 19 the second harmonic (2ω) to that which is transparent for the second harmonic Area 14 is guided. This construction has the particular advantage that the extremely high reflectivity of the total internal reflection can be used.

A fifth embodiment is shown in FIG. 5, in which the active laser medium is formed in the form of a square prism 42. The active medium 42 is excited by the radiation 3 from three diode lasers, so that three adjacent oscillators (fundamental wave (co)) with linear ring resonators are created. Three of the surfaces of the square prism 42 are highly reflective for the fundamental (co), while the lower right end face in FIG. 5, comparable to the corresponding end face of the radiation guiding prism 34 in FIG. 4, is coated with an anti-reflective coating for the fundamental wave (co). This end face is assigned a doubler etalon 19, the first face 7 of which is coated with an anti-reflective coating for the fundamental wave (ω), while for the second harmonic (2ω), like the opposite, parallel second face 9, it is coated with a highly reflective coating . The second harmonic (2co) is in turn coupled out at the surface area 14, so that an output beam 12 is formed, the power of which is composed of the power of the three individual laser oscillators 1. Essentially only two components are required for this arrangement, in addition to the diode laser for optical pumping, in the form of the active medium 42 (Laseφrisma) and the doubler etaion 19. For higher scaling, further oscillators can be generated by means of further diode pump lasers, the radiation of which is added to the radiation of the three laser oscillators 1 shown in FIG. 5 by means of the doubler stage 19.

While FIGS. 1 to 5 show five embodiments with ring oscillators, FIGS. 6, 7 and 8 show structures of various linear oscillators in which the structure according to the invention is implemented.

The linear resonators, as shown in FIGS. 6, 7 and 8, have two resonator end mirrors 44, between which an active medium 52 is arranged. Furthermore, a doubler etalon 48 is positioned in the beam path between the active medium 52 and the right-hand resonator end mirror 44. The left resonator end mirror 44, which is highly reflective for the fundamental wave (co), is used to pump by means of pump beams, which in turn are diode laser radiation 3. The active medium excited by means of the spot radiation 3 emits three basic periods (ω), so that three linear oscillators 11 stand side by side between the resonator end mirrors 44, in the doubler etalon 48, which has its first surface 7 and its second surface 9 under one is positioned at a suitable angle to the fundamental radiation (co), the second harmonic (2co) is generated in the two propagation directions, indicated by the respective double arrows within the etalon 48. The doubler etalon 48 is designed such that the second harmonic (2co) generated by the fundamental wave (co) running on the left is reflected in the other direction of propagation, so that in FIG. 6 in the upper area of the etalon 48 the first surface 7 on the surface area 14, which is designed to be anti-reflective for the second harmonic (2co), while the first and second surfaces 7 and 9 are (anti-reflective) coated for the fundamental (co) and highly reflective for the second harmonic , is coupled out as an output beam 12. Again, the power of the output beam 12 is additively composed of the powers of the three linear individual resonators 21. Since the second harmonic (2ω) is generated in two directions within the doubler ettaion 48, it is advantageous to chamfer the lower end face 49 of the etalon 48 and to orient it to the first and second surfaces 7, 9 in such a way that the second harmonic (2ω), which is reflected towards this surface, is reflected back with only one reflection in order to lead it to the coupling-out surface area 14. In this way the reflections and thus the reflection losses in this area of the etalon 48 can be kept low.

It is again clear that by simply adding further linear oscillators 21, the power of the laser arrangement, i.e. the power of the output beam 12, which is doubled in frequency, can be scaled upwards.

The seventh embodiment, as shown in FIG. 7, shows the basic structure as described with reference to FIG. 6. In addition to 6, a λ / 4 plate 45 is inserted on both sides of the active medium 52. Through these λ / 4 plates 45, the polarizations of the fundamental waves (co) running to the left and to the right are placed in such a way that the polarizations of these opposing fundamental waves (co) running to the left and right are perpendicular to one another. If the etalon-shaped doubler 48 is now phase-adjusted and intended for the clockwise wave, then the phase-matching condition for the counter-clockwise wave is not met. This means that a second harmonic (2co) is generated only by the clockwise fundamental wave (co), but not for the counterclockwise fundamental wave (co), as is shown by the arrows running in one direction within the doubler stage 48 of FIG. 7 is indicated, generated. The second harmonic (2co) generated by the individual laser oscillators 21 is coated by means of the etalon 48, the first surface 7 and second surface 9 of which are in turn coated for the fundamental (ω) antireflectively, but highly reflective for the second harmonic (2co) ¬ brought together and an output beam 12 (2ω) coupled out over the surface area 14. This embodiment with the so-called "twisted mode" also leads to the avoidance of spatial, so-called "hole-burning", which increases the performance stability.

On the basis of the embodiments in FIGS. 1 to 7, doubler crystals were shown, each of which is a one-piece etalon. In the eighth embodiment according to FIG. 8, which essentially represents a linear resonator, as is also shown in FIG. 7, each linear oscillator 21 is assigned a respective doubler crystal 50. Each of these doubler crystals 50 in turn has a first surface 7 and a second surface 8, which are each antireflectively coated for the fundamental radiation, and highly reflective for the second harmonic (2ω). By suitable dimensioning, positioning and orientation, As shown schematically in FIG. 8, the second harmonics (2co) generated in the doubler crystals 50 are shaped and reflected on the second surface 9 to the adjacent doubler crystal 50, where they emerge from the lateral end surface 53 which is coated for the second harmonic (2co) with an anti-reflective coating, emerge and enter the corresponding lateral end face 54 of the adjacent doubler crystal part 50, which is also coated with an anti-reflective coating for the second harmonic, strike the corresponding first face 7, are reflected from there to the second face 9 and are reflected by there in turn are directed to the end face 53, exit there and enter the next doubler crystal 50 in each case. In the area of the last doubler crystal part 50, the upper doubler crystal in FIG. 8, the output beam 12 is then coupled out via the end face 53. This embodiment has the advantage that precisely when an active medium 52 is assigned to each laser oscillator, as shown in FIG. 8, so that the individual linear resonators 21 are spaced apart from one another more than, for example, in the embodiment of the figure 7 is the case, by means of the individual doubler crystals 50, a larger offset to one another can be generated in order to additively bring together the radiation component in the form of the second harmonic (2ω) of the respective linear oscillators 21.

FIG. 9 shows a single doubler crystal 50, as used in the arrangement in FIG. 8, the outlet-side end face 53 being arched, in contrast to the illustration in FIG. 8. Such a measure can be advantageous not only at the exit surface 53 but also at the respective entry surfaces 54 in order to match the caustics of the second harmonics (2ω) generated in the respective laser oscillators 21 to one another. The use of the doubler crystals 50 assigned to each linear oscillator 21 can be used in an analogous manner in the ring oscillators shown and described in the embodiments of FIGS. 1 to 6.

As can be seen from the above description, in particular on the basis of the various exemplary embodiments, the measures according to the invention offer the advantages of a low thermal load on the optical components and the simple and virtually unlimited scalability of the laser arrangements in relation to frequency-doubled radiation. Due to mechanical structures that are required for the individual laser oscillators 1 or the field arrangement, the distances can be very large, as is shown schematically in FIG. 10 with the distance "D". In order to bring the beams closer together and to be able to keep the dimensions of the etalon 48 to acceptable dimensions, an optical arrangement 60 is used, which is composed of a first deflection element 61 and a second deflection element 61, which each have stair-shaped mirror surfaces 63 which are stepped or are arranged at different distances from the laser oscillators 1 such that the distance between the two beams, denoted by "d", approximates on the output side of the second deflecting element 62 becomes. The double deflection can be designed such that the same resonator lengths of the individual laser resonators are achieved with simultaneous approach (or distance).

Claims

claims

1. Laser arrangement with at least two individual laser oscillators, the radiation of the laser oscillators being bundled by means of optical components, characterized in that the fundamental radiation of the respective oscillator is doubled in frequency by a nonlinear crystal and that the respective radiation is achieved by means of an optical, dichroic com components are merged coaxially overlapping.

2. Laser arrangement according to claim 1, characterized in that the dichroic component is the frequeπz doubling crystal.

REPLACEMENT BUTT (RULE 26)

3. Laser arrangement according to claim 1 or claim 2, characterized gekennzeich¬ net that the laser oscillators a common, non-linear crystal is assigned.

4. Laser arrangement according to one of claims 1 to 3, characterized gekennzeich¬ net that the non-linear crystal has two parallel surfaces which form entrance, exit and / or reflection surfaces for the radiation.

5. A laser arrangement according to claim 4, characterized in that the individual laser oscillators each have a ring resonator.

6. Laser arrangement according to claim 5, characterized in that the Kri¬ stall is assigned a radiation deflecting function.

7. Laser arrangement according to claim 6, characterized in that the Kri¬ stall has an entry and a reflection surface, the entry surface for the fundamental (co) is coated with an anti-reflective coating and is highly reflective for the second harmonic (2ω) and the reflection surface for the fundamental wave (ω) and the second harmonic (2co) is highly reflective.

8. Laser arrangement according to one of claims 4 to 7, characterized gekennzeich¬ net that the entrance surface or the reflection surface has a coupling-out surface for the second harmonic (2ω).

9. Laser arrangement according to claim 7 or claim 8, characterized gekennzeich¬ net that the entrance surface and the reflecting surface are ge parallel to each other.

10. Laser arrangement according to one of claims 1 to 9, characterized gekennzeich¬ net that the laser oscillators a common Festköφmedium is assigned.

11. Laser arrangement according to claim 10, characterized in that the solid body is designed as a prism, with at least two surfaces forming reflection surfaces of the ring resonator.

12. Laser arrangement according to claim 10, characterized in that the solid body is designed as an etalon, the one surface having an anti-reflective coating for the fundamental (co) and the other surface having a highly reflective coating for the fundamental (co).

13. Laser arrangement according to one of claims 1 to 9, characterized thereby that each laser oscillator has a separate solid body medium.

14. Laser arrangement according to one of claims 1 to 4, characterized gekennzeich¬ net that the laser oscillators each form a linear resonator.

15. Laser arrangement according to claim 14, characterized in that the laser serosilators are arranged parallel to one another.

16. Laser arrangement according to claim 14 or claim 15, characterized gekenn¬ characterized in that the crystal has a first surface and an opposite second surface, both surfaces for the fundamental (co) are anti-reflective coated and for the second harmonic (2ω) are coated with a highly reflective coating.

17. Laser arrangement according to claim 14 or claim 15, characterized gekenn¬ characterized in that the crystal has a first surface and an opposite second surface, the first surface for the fundamental (ω) is anti-reflective and coated for the second harmonic (2co ) is coated with a highly reflective coating and the second surface for the fundamental wave (ω) and the second harmonic (2ω) is coated with a highly reflective coating.

18. Laser arrangement according to one of claims 14 to 17, characterized gekenn¬ characterized in that one of the two surfaces has a coupling-out surface for the second harmonic (2ω).

19. Laser arrangement according to one of claims 14 to 18, characterized gekenn¬ characterized in that the two surfaces are formed parallel to each other.

20. Laser arrangement according to one of claims 14 to 19, characterized gekenn¬ characterized in that the laser oscillators is assigned a common solid body medium.

21. Laser arrangement according to one of claims 14 to 20, characterized gekenn¬ characterized in that each laser oscillator has a separate solid medium.

22. Laser arrangement according to one of claims 14 to 20, characterized gekenn¬ characterized in that a λ / 4 plate is used on both sides of the solid medium within the resonator.

23. Laser arrangement according to one of claims 16 to 21, characterized gekenn¬ characterized in that the crystal has a third surface which is highly reflective for the second harmonic (2ω) and the second harmonic generated by the fundamental wave (co) running to the left (2ω) reflected back.

24. Laser arrangement according to claim 1, characterized in that the dichroic component has a first surface and an opposite second surface, the first surface for the fundamental wave (ω) is highly reflective and for the second harmonic (2ω) is anti-reflective.

25. Laser arrangement according to claim 24, characterized in that the individual laser oscillators each have a ring resonator.

26. Laser arrangement according to claim 24, characterized in that the laser seriocilators each form a linear resonator.

27. Laser arrangement according to one of claims 24 to 26, characterized gekenn¬ characterized in that the laser oscillators is assigned a common, non-linear crystal.

28. Laser arrangement according to one of claims 23 to 27, characterized gekenn¬ characterized in that the laser oscillators is assigned a common solid body medium.

29. Laser arrangement according to one of claims 1 to 28, characterized gekennzeich¬ net that the non-linear crystal and / or the dichroic component is (are) divided into individual segments which are arranged at a distance from one another, each segment having an exit surface and / or has an entrance surface which is antireflective for the second harmonic (2co).

30. Laser arrangement according to claim 29, characterized in that the entry and / or exit surface (s) have a curvature such that the caustics of the second harmonic (2ω) generated in the respective laser oscillator are matched to one another.

31. Laser arrangement according to one of claims 1 to 30, characterized gekennzeich¬ net that an optical arrangement is used in the beam path of at least one laser oscillator in the beam path between the dichroic components and the active medium, which the distances between the at least one Laser oscillator changed to at least one other of the laser oscillators.

32. Method for scaling the power of frequency-doubled lasers, characterized in that at least two laser oscillators are arranged side by side and the fundamental wave is doubled in frequency and that the doubled radiation is brought together coaxially.

33. The method according to claim 32, characterized in that the laser oscillators are operated decoupled.

34. The method according to claim 32 or claim 33, characterized in that the individual laser oscillators are operated at slightly different frequencies of the fundamental wave from each other.