JP2009194176A - Solid laser device and laser machining method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid laser device and laser machining method which can uniformize an optical path length with respect to a positional change of a direction orthogonal to a zigzag optical path. <P>SOLUTION: This solid laser device comprises: a laser medium which has an excitation area to which active ions are added, in the slab type form; and an image inversion optical means which inverts an image in beams which have passed a first optical path inside the excitation area to let the beams pass a second optical path inside the excitation area. In the solid laser device and laser machining method, the first optical path is on one side in relation to a symmetrical face of the excitation area, and the second optical path is on the other side in relation to the symmetrical face and is substantially in parallel to the first optical path. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a solid-state laser device and a laser processing method.

  In a solid-state laser such as Nd: YAG, excitation is performed by light emission from a lamp or a semiconductor laser. This excitation light is absorbed by laser active ions distributed in a crystal or glass which is a solid-state laser medium. The laser active ion absorbs excitation light and emits laser light having a longer wavelength than that.

  The energy corresponding to the difference between the excitation wavelength and the emitted light wavelength is heat. The generated heat is large in the high power laser, and the solid laser medium is cooled to radiate heat. In this case, since heat is diffused through the outer peripheral portion, a temperature distribution is generated in which the central portion is high and the outer peripheral portion is low. This temperature distribution causes a refractive index distribution and a stress distribution.

  In the slab type solid-state laser, when the total reflection is performed between the upper and lower surfaces of the plate-like medium to form a zigzag optical path, the beam alternately passes through the temperature distribution change in the vertical direction alternately. For this reason, the temperature distribution can be made uniform in the beam cross section, and the quality of the outgoing beam can be improved.

There is a technical disclosure example for performing aberration control of a zigzag slab laser (Patent Document 1). In this example of technical disclosure, a one-dimensional aberration corrector is used to compensate for non-uniformity of the wavefront in the direction across the zigzag direction of the beam in the slab.
However, even if this example of technical disclosure is used, there is an influence of the temperature distribution in the direction orthogonal to the zigzag optical path, and it cannot be said that the beam quality is sufficiently improved.
JP-A-9-18071

  Provided are a solid-state laser device and a laser processing method capable of making the optical path length uniform with respect to a position change in a direction orthogonal to the zigzag optical path.

  According to one aspect of the present invention, a laser medium having an excitation region to which active ions are added and having a slab shape and a beam that has passed through the first optical path in the excitation region are image-inverted, Image inversion optical means for passing a second optical path in the excitation region, wherein the first optical path is on one side with respect to a symmetry plane of the excitation region, and the second optical path is the symmetry A solid-state laser device is provided that is on the other side of the surface and substantially parallel to the first optical path.

  According to another aspect of the present invention, the beam is generated using the solid-state laser device, the workpiece is irradiated with the beam, and the vicinity of the irradiation point on the workpiece is melted. A featured laser processing method is provided.

   Provided are a solid-state laser device and a laser processing method capable of making the optical path length uniform with respect to a position change in a direction orthogonal to the zigzag optical path.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a solid-state laser device according to the first embodiment of the present invention. FIG. 1A is a plan view, FIG. 1B is a cross-sectional view taken along the line AA, and FIG. 1C is a graph of the refractive index distribution in the cross section taken along the line BB. Specifically, the present embodiment is an oscillator including an optical resonator using a mirror. The slab-shaped laser medium 10 includes a first excitation region 12 to which a laser active ion such as neodymium (hereinafter referred to as Nd), which is one of rare earth elements, is added, a second excitation region 1414, and adjacent to them. And the non-excitation region 16 to which the laser active ions are not added are integrally molded.

  The non-excitation region 16 is a transparent polycrystalline YAG (yttrium aluminum garnet) ceramic or the like, and the first excitation region 12 and the second excitation region 14 are Nd or the like in a transparent polycrystalline YAG ceramic to which Nd is added.

  Further, the first excitation region 12 and the second excitation region 14 are integrally molded using a sintering process or the like so as to be surrounded by the non-excitation region 16. In this case, the surfaces of the first and second excitation regions 12 and 14 may be exposed on the surface of the laser medium 10 or may be covered. The first and second excitation regions 12 and 14 absorb the excitation light Gex and become high temperature. However, if the surface is covered with the non-excitation region 16 as shown in FIG. 1, the high temperature surface can be protected. The first surface 10a and the second surface 10b of the laser medium 10 face each other as shown in FIG.

  The beam GT passes through the optical path G1, the optical path G2, and the like, for example. The first optical paths G1a, G2a in the first excitation region 12 through which the beam GT passes are on one side with respect to the symmetry plane 26 orthogonal to the first and second surfaces 10a, 10b of the laser medium 10. The second optical paths G1b and G2b in the second excitation region 14 through which the beam GT passes are on the other side with respect to the symmetry plane 26 and are substantially parallel to the first optical path.

  As shown in FIG. 1, it is more preferable that the optical paths G1 and G2 be parallel to the symmetry plane 26 because optical coupling with external optical means such as a mirror can be simplified. In FIG. 1, a direction orthogonal to the first surface 10a and the second surface 10b is an x axis, a direction parallel to the symmetry surface 26 is a z axis, and a direction orthogonal to the x axis and the z axis is a y axis.

  Further, excitation light Gex is incident from lateral surfaces (edge surfaces) 10e and 10f which are orthogonal to the first and second surfaces 10a and 10b and parallel to the z-axis. Nd that has absorbed the excitation light Gex causes stimulated emission. As the excitation light Gex, for example, semiconductor laser light having a wavelength of 810 nm is used. The semiconductor laser light is guided by a light guiding fiber, and its end portion is disposed close to the lateral surfaces 10 e and 10 f of the laser medium 10. In this case, it is efficient to irradiate the cross sections of the first excitation region 12 and the second excitation region 14 with the excitation light Gex in the xz plane, and the non-excitation region 16 does not generate heat. Can be kept at a lower temperature.

  When this embodiment is used as an oscillator, the beam GT passes between the total reflection mirror 20 and the partial reflection mirror 24. The optical path G1 through which the beam GT passes is the optical path G1a in the first excitation region 12, the optical path G1b in the second excitation region 14, and the image inverting optical means 22 having a trapezoidal cross section sandwiched therebetween. Optical path G1c. An optical path G2 through which the beam GT passes is an optical path G2a in the first excitation region 12, an optical path G1b in the second excitation region 14, and an optical path in the image inverting optical means 22 sandwiched between them. G2c. Actually, an optical path also exists in the space between them, but since it has the same length with respect to the optical path G1 and the optical path G2, it will be omitted. As the image inverting optical means 22, an image inverting prism such as a Dove prism can be used.

  The Nd-doped YAG excited by the excitation light Gex stimulates and emits a laser beam of about 1.06 μm. Therefore, the amplification gain generated in the first and second excitation regions 12 and 14 causes laser oscillation by the Fabry-Perot resonator formed between the total reflection mirror 20 and the partial reflection mirror 24, and the partial reflection mirror 24. The beam GT can be taken out from the outside. In this configuration, the excitation region and the image inverting optical means 22 have a common symmetry plane 26.

  The laser medium 10 has a third surface 10c orthogonal to the lateral surfaces 10e and 10f, and obliquely intersecting the first and second surfaces 10a and 10b, and a fourth surface 10d. That is, the third surface 10c and the first surface 10a intersect at an angle θ, and the fourth surface 10d and the second surface 10b intersect at an angle θ. In this case, for example, the wedge-shaped angle θ is selected so that the beam GT incident from the third surface 10c and the fourth surface 10d causes total reflection on the first and second surfaces 10a and 10b. In this case, it is preferable to optically polish the first and second surfaces 10a and 10b to increase the reflectance.

  As shown in FIG. 1B, the second optical path G1b is a zigzag optical path in the xz plane. Similarly, the first optical paths G1a and G2a and the second optical path G2b are zigzag optical paths in the xz plane. The excitation region and the non-excitation region contain a YAG ceramic material in the composition, and the refractive index difference is small, so that the optical path is hardly bent at the interface.

  FIG. 2 is a diagram for explaining a beam traveling in a zigzag optical path. 2A is a schematic diagram showing the vicinity of the wedge shape of the laser medium 10, and FIG. 2B is a graph showing the temperature distribution in the x-axis direction. The actual beam GT has a cross-sectional area as shown in FIG. 2A, and has many optical paths passing through the cross-section. In this figure, the cross section of the beam GT has a circular shape with a diameter of 2a and travels along the zigzag optical path Gz while repeating total reflection inside the laser medium 10.

If the refractive index of the YAG ceramic material constituting the laser medium 10 is 1.8 and the outside is air, the critical angle θ _C is about 34 degrees, and total reflection occurs at an incident angle α larger than the critical angle θ _C. That is, the angle θ of the cross section of the laser medium 10 is determined so that the incident angle α is larger than the critical angle θ _C.

In addition, it is more preferable that the incident angle β to the third surface 10c and the fourth surface 10d is in the vicinity of the Brewster angle θ _{B because} the transmittance of p-polarized light can be close to 100% and the light extraction efficiency can be improved. When the refractive index of the laser medium 10 is 1.8, the Brewster angle θ _B is about 29 degrees.

  The beam GT incident on the fourth surface 10d of the laser medium 10 having the thickness in the x-axis direction T, the length in the z-axis direction L, and the wedge-shaped cross section angle θ travels in the zigzag optical path Gz. A non-passing region Q of the beam GT is generated in the laser medium 10. It is more preferable to appropriately select the angle θ and the length L in the laser medium 10 because this non-passage region Q can be reduced and the laser medium 10 can be made compact.

  Since the optical output of the excitation light Gex is high, the first and second surfaces 10a and 10b are cooled to dissipate heat generated in the laser medium 10. Even in this case, as shown in FIG. 2B, the central portion (near x = T / 2) of the laser medium 10 having the thickness T becomes high temperature, and a temperature distribution represented by, for example, a square curve is generated. Based on this temperature distribution, the refractive index change rate dn / dT is, for example, several ppm in a YAG material. Further, based on this temperature distribution, compression occurs near the center and tensile stress occurs near the surface.

  As shown in FIG. 1B, the beam GT travels along a zigzag optical path G1b due to total reflection in the xz plane, and passes through a change due to the temperature distribution 81 in the x-axis direction obliquely and alternately, to the temperature distribution 81. The refractive index distribution and the stress distribution based on it are made uniform in the x-axis direction. For this reason, even if a refractive index distribution or a stress distribution occurs, it becomes easy to obtain a high-quality beam with a uniform optical path length, a uniform wavefront, and a small beam divergence angle. When the refractive index distribution in the xz plane is negligible, the zigzag optical path is not necessary, but it is more preferable to use a zigzag optical path and make the refractive index in the x-axis direction uniform.

  On the other hand, in the yz plane, the excitation light Gex is incident from the lateral surfaces 10e and 10f to generate a temperature distribution 80 in the y-axis direction. For example, the temperature becomes maximum in the vicinity of the symmetry plane 26 as shown in FIG. ing. For example, a method of arranging a heat insulating material on the horizontal surfaces 10 e and 10 f and flattening the temperature distribution 80 can be considered, but adjustment is difficult due to heat generation of the laser medium 10. Although a method of exciting only the vicinity of the central portion of the laser medium 10 can be considered, there is a problem that excitation is insufficient and beam output is lowered.

  In FIG. 1, the first optical path G1a of the first excitation region 12 and the second optical path G1b of the second excitation region 14 are parallel to the symmetry plane 26, respectively. Similarly, the first optical path G2a and the second optical path G2b are parallel to the symmetry plane 26, respectively. The beam GT that has passed through the first optical path G1a passes through the optical path G1c in the image inverting optical means 22, and passes through the second optical path G1b with the y-axis direction position being switched in plan view. Note that the light reflected by the partial reflection mirror 24 travels in reverse on this optical path. Similarly, the beam GT that has passed through the first optical path G2a passes through the optical path G2c in the image inverting optical means 22, passes through the second optical path G2b, with the y-axis direction position switched in plan view. An arrow shown in FIG. 1A represents an image posture V in the xy plane, and the image posture V is reversed toward the traveling direction after passing through the image reversing unit 22.

  In FIG. 1C, the vertical axis is the refractive index (n) that varies depending on the temperature distribution 80, and the horizontal (y) axis is the distance from the symmetry plane 26. In the xy plane, the refractive index of the first optical path G1a is n1, and the refractive index of the second optical path G1b is n2 (n1 <n2). The refractive index of the first optical path G2a is n3, and the refractive index of the second optical path G2b is n4 (n4 <n3). Since the optical path in the xz plane is a zigzag optical path, the refractive index n changes depending on the position in the x-axis direction. However, since the change in the refractive index n along the zigzag optical path can be averaged in the x-axis direction, the refractive index n shown in FIG. 1C is considered to depend only on the position in the y-axis direction.

  The optical path length is represented by the product of the refractive index n and the geometric length. As shown in FIG. 1C, when the gradient of the refractive index distribution changes monotonously and is substantially symmetrical with respect to the symmetry plane 26, the average refractive index of n1 and n2 and the average refractive index of n3 and n4 are It is easy to get close. Since the first and second excitation regions 12 and 14 have the same length in the z-axis direction, the optical path length of G1 and the optical path length of G2 can be made substantially the same. That is, as shown in FIG. 1A, even if the position in the xy plane through which the beam GT passes is changed by changing the y-axis direction position in plan view, it becomes easy to make the optical path length uniform. . In addition, it is more preferable that the gradient of the refractive index distribution in the excitation regions 12 and 14 is closer to the straight line because the average refractive index can be made closer.

  FIG. 3 shows a solid-state laser device according to a comparative example. 3A is a schematic plan view, FIG. 3B is a schematic cross-sectional view taken along the line CC, and FIG. 3C is a graph of the refractive index distribution in the xy plane. When the comparative example is an oscillator, the beam GT passes between the total reflection mirror 120 and the partial reflection mirror 124. The optical path G11 has a first optical path G11a in the first excitation region 112 and a second optical path G11b in the second excitation region 114. The optical path G12 includes a first optical path G12a in the first excitation region 112 and a second optical path G12b in the second excitation region 114. The amplification gain generated in the first and second excitation regions 112 and 114 generates laser oscillation in the Fabry-Perot resonator formed between the total reflection mirror 120 and the partial reflection mirror 124, and the external reflection from the partial reflection mirror 124. The beam GT is taken out. In this configuration, the laser medium 110 and the mirrors 130 and 131 have a common symmetry plane 126.

  The first optical path G11a in the first excitation region 112 and the second optical path G11b in the second excitation region 114 are parallel to the symmetry plane 126, respectively. Similarly, the first optical path G12a and the second optical path G12b are parallel to the symmetry plane 126, respectively.

  The beam GT passes through the first optical paths G11a and G12a, is reflected by the mirrors 130 and 131, and passes through the second optical paths G11b and G12b. Therefore, the first optical path G11a and the second optical path G11b are substantially symmetric with respect to the symmetry plane 126, and the first optical path G12a and the second optical path G12b are also substantially symmetric with respect to the symmetry plane 126. That is, in the comparative example, the image posture V indicated by the arrow is the same in the traveling direction between the first optical paths G11a and G12a and the second optical paths G11b and G12b, and the image is not inverted.

  FIG. 3C shows the position dependency of the refractive index (n) based on the temperature distribution 180 in the y-axis direction. In the xy plane, the refractive index in the first optical path G11a and the second optical path G11b is n5. Further, the refractive index in the first optical path G12a and the second optical path G12b is n6. Since n5 <n6, the optical path length G11 having the first optical path G11a and the second optical path G11b is shorter than the optical path length G12 having the first optical path G12a and the second optical path G12b. Since the refractive indexes are different as described above, the optical path G11 and the optical path G12 have different optical path lengths, and the spread angle of the beam GT tends to increase in the yz plane. That is, the refractive index near the center becomes a high refractive index, the wavefront spreads, the beam divergence angle increases, and the beam quality deteriorates.

  On the other hand, in this embodiment, it is easy to make the optical path length uniform. For example, a beam GT having a cross section as shown in FIG. 2A has a uniform optical path length and a uniform wavefront even with respect to a position change in the y-axis direction in the xy plane, and the beam spread in the yz plane. It is easy to reduce the angle and improve the beam quality. Similar effects can be easily obtained for the stress distribution based on the temperature distribution 80.

  FIG. 4 is a schematic diagram illustrating a modification of the laser medium. FIG. 4A is a plan view, and FIG. 4B is a graph showing the refractive index distribution of the cross section along the line BB. When the distance S between the first excitation region 12 and the second excitation region 14 is changed, the dependence of the temperature distribution 82 on the y-axis direction can be controlled. In the vicinity of the lateral surfaces 10e and 10f, since the intensity of the excitation light Gex is high, the absorption in the first and second excitation regions 12 and 14 is large, and the temperature rises. As the distance S increases, the temperature reaches a maximum in the vicinity of the lateral surfaces 10e and 10f, and a bimodal temperature distribution 82 in which the temperature is minimized in the vicinity of the symmetry plane 26 can be obtained. That is, the temperature distribution 82 can be controlled by the interval S.

  As shown in FIG. 4B, the gradient of the bimodal refractive index distribution corresponding to the temperature distribution 82 changes monotonously and is substantially symmetric with respect to the symmetry plane 26. In this case, the refractive index of the first optical path G1a is n1, and the refractive index of the second optical path G1b is n2. The refractive index of the first optical path G2a is n3, and the refractive index of the second optical path G2b is n4. It is easy to bring the average refractive index of n1 and n2 close to the average refractive index of n3 and n4. In addition, it is more preferable that the gradient of the refractive index distribution in the excitation regions 12 and 14 is closer to the straight line because the average refractive index can be made closer.

  Since the first and second excitation regions 12 and 14 have the same length in the z-axis direction, the optical path length of the optical path G1 having the first and second optical paths G1a and G1b, and the first and second optical paths G2a. , G2b and the optical path length of the optical path G2 can be made substantially the same. That is, even if the position in the xy plane through which the beam GT passes is changed by switching the position in the y-axis direction in plan view, it becomes easy to make the optical path length uniform. In this way, the first optical path and the second optical path can be interchanged by the image inverting optical means 22, and the optical path length can be made uniform with respect to the change in the y-axis direction position.

  FIG. 5 is a schematic diagram of a solid-state laser apparatus according to the second embodiment. FIG. 5A is a plan view, and FIG. 5B is a cross-sectional view taken along line DD. The beam GT passes through the first optical path G1a and the second optical path G1b which are opposite to each other with respect to the symmetry plane 27 orthogonal to the first and second surfaces 10a and 10b of the common excitation region 11. This makes it easy to lengthen the excitation region 11 in the z-axis direction and increase the amplification gain and laser output. Further, the planar shape elongated in the z-axis direction makes it easy to improve heat dissipation. The length in the z-axis direction can be about 200 mm, for example.

  Note that the laser medium 10 may be configured only by the excitation region. However, it is more preferable to arrange the excitation region in the central region where the excitation light Gex is easily irradiated and to provide the non-excitation region around the central region in order to increase the excitation efficiency and the cooling effect. In this case, the excitation region 11 may be covered with the non-excitation region 16.

  FIG. 6 is a schematic diagram of a solid-state laser device according to a modification of the second embodiment. FIG. 6A is a plan view, and FIG. 6B is a cross-sectional view on the symmetry plane 27. In the case of this modification, the tip of the image inverting optical means 22 forms an acute angle. When the laser medium 10 has a planar shape elongated in the z-axis direction, the first optical path G1a passes near the tip M of the image inverting optical means 22. In this case, a high beam output may be absorbed and the tip M may deteriorate. For this purpose, a reflective layer or a light shielding region is provided at the tip M. A light shielding region N may be provided in the laser medium 10 facing the image inverting optical means 22. If it does in this way, degradation of tip part M can be controlled.

  FIG. 7 is a schematic diagram of a solid-state laser apparatus according to the third embodiment. FIG. 7A is a plan view, and FIG. 7B is a cross-sectional view taken along the line AA. The solid-state laser device of this embodiment is an amplifier. That is, the signal light Ggn from the seed light source 40 enters the laser medium 10 and emits a beam GT that is amplified light that has passed through the first optical path G1a, the image inverting optical means 22, and the second optical path G1b to the outside. . Also in this case, a beam GT with a uniform optical path length and improved quality can be obtained.

  The solid-state laser device according to this embodiment can emit a beam to a long distance in the air. For this reason, it becomes easy to accurately irradiate a beam toward a remote target.

  FIG. 8 is a schematic diagram for explaining a laser processing method using the solid-state laser device of this embodiment as an oscillator. The solid-state laser device 50 includes a basic configuration illustrated in FIG. 1, a Q switch 52, a control unit 62, an excitation light source 54, and a cooling unit 56.

  A Q switch 52 is disposed between the first excitation region 12 and the total reflection mirror 20. The Q switch 52 is made of a piezoelectric material, changes the direction of the optical axis by changing the voltage on or off, and controls the optical resonator on or off. For this reason, a beam having a high pulse peak output can be obtained. The controller 62 outputs a Q switch control signal C1.

  The excitation light source 54 irradiates the lateral surfaces 10e and 10f of the laser medium 10 with excitation light Gex from, for example, semiconductor lasers arranged in parallel. A flash lamp may be used as the excitation light source. The excitation regions 12 and 14 absorb the excitation light Gex, Nd is excited to enable stimulated emission, and oscillation is generated by the optical resonator to emit laser light. The controller 62 outputs the excitation light control signal C2.

  Note that an amplifier shown in FIG. 7 may be used instead of the solid-state laser device including the Q switch and the oscillator of FIG. In this case, the signal light Ggn is pulse-modulated using, for example, a Q switch, and amplified by stimulated emission to obtain a beam GT.

  A cooling unit 56 is provided on the first and second surfaces 10 a and 10 b of the laser medium 10. Since the excitation regions 12 and 14 that have absorbed the excitation light Gex generate heat, they are cooled. For example, it is possible to use a method using thermal conduction in which a surface coating using a low refractive index material is applied to the laser medium 10 and heat is radiated through a copper block. Moreover, the method using the heat convection which circulates cooling water can also be used. The controller 62 outputs a cooling unit control signal C3.

The beam GT taken out from the solid-state laser device 50 through the partial reflection mirror 24 is directed toward the workpiece 70 by a mirror 58, for example. If necessary, beam shaping is performed by the beam shaping optical unit 60, and a desired beam GT is irradiated onto the workpiece 70. Since the beam GT has a uniform wavefront, it is easy to focus using a lens or the like.
The controller 62 outputs a beam shaping control signal C4.

  The beam GT having a high peak output melts the vicinity of the irradiation point 72 even if it is a thick steel plate, for example. The workpiece 70 can be cut or welded by moving the beam GT or the workpiece 70. The average output of the pulse-driven beam GT can be, for example, about several kW to 100 kW.

  In the laser processing method according to the present embodiment, it is possible to use a beam GT having a uniform optical path difference in the cross section of the beam GT, uniform wavefronts, and a small divergence angle. For this reason, it becomes easy to perform laser processing at a position away from the solid-state laser device 50. A method of laser processing from a distance using a high-power beam is preferable from the viewpoint of safety and workability.

  The embodiments of the present invention have been described above with reference to the drawings. However, the present invention is not limited to these embodiments. Those skilled in the art have made design changes with regard to the laser medium, active ions, image inversion optical means, optical components, optical resonator, seed light source, excitation light source, cooling part material, size, shape, arrangement, etc. that constitute the solid-state laser device Even if it is a thing, unless it deviates from the main point of this invention, it is included in the scope of the present invention.

1 is a schematic diagram of a solid-state laser device according to a first embodiment of the present invention. Schematic diagram explaining the zigzag optical path Schematic diagram of solid state laser device according to comparative example Schematic diagram showing a modification of the laser medium Schematic diagram of the solid-state laser device according to the second embodiment The schematic diagram of the solid-state laser apparatus concerning the modification of 2nd Embodiment Schematic diagram of a solid-state laser device according to a third embodiment Diagram explaining the laser processing method

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Laser medium, 11 Excitation area | region, 12 1st excitation area | region, 14 2nd excitation area | region, 16 Non-excitation area | region, 20 Total reflection mirror, 22 Image inversion optical means, 24 Partial reflection mirror, 26, 27 Symmetry surface, 40 Seed light source, 50 solid-state laser device, 56 cooling unit, 70 workpiece, 72 irradiation point, 80, 82 temperature distribution, G1, G1a, G1b, G2, G2a, G2b optical path, GT beam, Ggn signal light, Gex excitation light

Claims (12)

A laser medium having an excitation region doped with active ions and having a slab shape;
An image inverting optical means for inverting the image of the beam that has passed through the first optical path in the excitation region and passing the second optical path in the excitation region;
With
The first optical path is on one side with respect to the plane of symmetry of the excitation region;
The solid-state laser device, wherein the second optical path is on the other side with respect to the symmetry plane and substantially parallel to the first optical path. The laser medium further has a non-excitation region to which the active ions are not added,
The solid-state laser device according to claim 1, wherein the excitation region and the non-excitation region are integrally formed. The excitation region has a first excitation region and a second excitation region,
3. The solid-state laser device according to claim 2, wherein the first excitation region and the second region are substantially symmetrical with respect to the symmetry plane and are separated from each other by the non-excitation region. . The laser medium includes a first surface, a second surface facing and substantially parallel to the first surface, a third surface intersecting the first surface at a predetermined angle, and the third surface. A fourth surface substantially parallel to the surface of
The predetermined angle is set so that the beam travels in a zigzag optical path while repeating total reflection on the first and second surfaces. Solid state laser device.   In the first optical path and the second optical path, the position in the orthogonal direction to the symmetry plane is switched in plan view by the image inverting optical means, and even if a temperature distribution occurs in the orthogonal direction, the beam of the beam 5. The solid-state laser device according to claim 1, wherein the optical path length is substantially uniform without depending on the position. 6.   The solid-state laser device according to claim 1, wherein the image inverting optical unit is an image inverting prism. The laser medium has a lateral surface substantially orthogonal to the first surface and substantially parallel to the symmetry surface;
The solid-state laser apparatus according to claim 4, wherein excitation light for exciting the active ions is incident from the lateral surface.   8. The solid state laser device according to claim 7, wherein a cooling unit is provided on the first and second surfaces. A total reflection mirror for reflecting the beam;
A partially reflecting mirror that reflects a portion of the beam and transmits another portion of the beam;
Further comprising
The beam is generated by an optical resonator constituted by the total reflection mirror and the partial reflection mirror,
The solid-state laser device according to claim 1, wherein the beam is emitted to the outside via the partial reflection mirror. A seed light source for injecting signal light into the excitation region;
9. The solid-state laser device according to claim 1, wherein the signal light is amplified in the first and second optical paths and emitted as the beam. The beam is generated using the solid-state laser device according to any one of claims 1 to 10,
A laser processing method, wherein the workpiece is irradiated with the beam, and the vicinity of the irradiation point on the workpiece is melted.   The laser processing method according to claim 11, wherein the workpiece in which the vicinity of the irradiation point is melted is cut or welded.

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