JP2001326405A - Solid-state slab laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-state slab laser device whose quality and output are high, whose stable output is variable, which is low-cost and whose high performance is realized easily. SOLUTION: Excitation light 130 by which a laser beam 120 advancing on the inside of two parallel slab laser mediums 110 and on the inside of their central-part space 111 is excited on the inside of the laser mediums 110 is radiated to nearly the whole face on outside faces of the laser mediums 110. A fixture 140 which fixes the laser mediums 110, an excitation light source 130 and its confinement part 145 are provided with a mirror surface 140 forming the central-part space 111, a reflecting surface 146 whose inner wall used to reflect excitation light 131 is a mirror surface so as to become a condensing face and an intermediate wall surface 147. The excitation light 130 is transmitted a plurality of times in nearly the whole region of the laser mediums 110. A gas is made to flow to the central-part space 111 from a gas introduction passage 142, and a cooling fluid is made to flow to the whole outside by a fluid channel 143 so as to cool the laser mediums 110. When the excitation light is incident on the whole end face on the thickness side of the slab-shaped laser mediums so as to be confined at the inside of the mediums, the confinement part can be made unnecessary.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state laser which is used in an oscillation device or an amplification device and is formed of a slab-shaped laser medium for generating a laser beam. The present invention relates to a low-cost, high-performance solid-state slab laser device that can be easily realized.

[0002]

2. Description of the Related Art Laser light having a wavelength of 1 μm or less generated by a solid-state laser using a solid-state laser medium has a relatively strong interaction with a substance and can be easily transmitted through an optical fiber. It is being widely used in the field of processing applications. Therefore, in order to improve the processing performance, a beam of a higher quality and higher output laser beam, which has a lateral mode close to the fundamental mode and has excellent light collecting characteristics, is required.

Conventionally, in this type of solid-state laser, high-intensity pumping light is applied to obtain a high output. High-intensity excitation light generates a temperature distribution inside the medium, which generally causes photothermal effects such as the thermal lens effect and thermal birefringence effect. Quality and decline. Therefore, with such a solid-state laser, a stable high output cannot be obtained, and the quality of the output beam also deteriorates.

Further, even if a high output can be realized by forming a resonator in combination with a lens or the like so as to compensate for the thermal lens effect, the thermal lens effect changes when the excitation intensity is changed over a wide range. It is difficult to maintain a stable output, and stable wide output variability cannot be obtained.

As a means for solving such a drawback, as shown in FIG. 7, a slab-shaped laser medium having a length L, a width W and a thickness T is directly replaced with a solid-state laser 100.
A solid slab laser was devised in which the laser beam 1020 forms a zigzag optical path by totally reflecting the inside 1011 of the solid-state laser 1000 on both side surfaces 1012. In this slab laser, in the case of an ideal two-dimensional temperature distribution, the direction of the internal temperature gradient coincides with the traveling direction of the laser beam, so that the laser beam does not receive the thermal lens effect.

However, in the example using one slab-shaped laser medium, a higher input is applied to the slab without thermally destroying the slab by increasing the aspect ratio with respect to the dimension of a cross section perpendicular to the longitudinal direction. However, since the cross-sectional shape of the medium becomes thinner and rectangular, the oscillation laser light includes higher-order transverse modes. On the other hand, a circular aperture can be inserted inside a resonator using such a solid-state laser in order to obtain a fundamental mode or low-order mode oscillation having a circular cross section. However, even with such a configuration, since the end of the slab-shaped laser medium deviates from the oscillation mode volume, the utilization efficiency of the input pump light is reduced. Therefore, only a part of the slab-shaped laser medium that is excited near the center part contributes to laser oscillation and amplification. For this reason, the efficiency of the fundamental mode or low-order mode laser oscillation required to realize a high-quality laser beam is reduced, and a high output cannot be obtained even when the generated laser beam is of high quality. . Further, there is a problem that the wavefront of the laser light is disturbed by a three-dimensional temperature distribution or stress distribution generated near the input / output surface of the slab.

A laser device using a slab-shaped laser medium and a solid-state laser capable of solving the above problems are disclosed in
-16397 and JP-A-4-30484. These are solid-state slab lasers in which two slab-shaped laser media are arranged at intervals and a laser beam is oscillated between them. In such a solid slab laser structure, while the aspect ratio of each of two slab media containing a laser medium can be increased, a slab formed including a transparent slab body or a space sandwiched between two slab media is provided. The thickness of the overall cross section of the laser-amplified medium has a degree of freedom that can be set to almost the same size as the diameter of the incident laser light. Therefore, there is an advantage that the efficiency does not decrease even in the oscillation of low-order mode laser light. is there.

FIG. 8 shows a laser device 1 having a composite slab structure disclosed in Japanese Patent Application Laid-Open No. Hei 4-16397.
100 is shown. In this case, two relatively thin slab-shaped laser amplification media 1110 are fused by sandwiching a central transparent slab material 1111 from both sides. In such a composite slab structure, since the laser amplification medium 1110 that absorbs the excitation light emitted from the outside of the laser amplification medium 1110 and generates heat is thin, it is easy to exhaust heat. The photothermal effect is hard to appear, and the slab is hardly thermally damaged.

However, in order to make the laser medium composite, it is necessary to adjust the refractive index of different laser medium materials to be fused to be the same so that no residual stress remains at the boundary surface. For this reason, it is necessary not only to make the refractive index of each material the same, but also to prepare the materials and to precisely control the fusion temperature so that their thermal expansion coefficients become the same. Therefore, there is a problem that the production of a composite slab having a size required for high output is complicated and extremely difficult.
Further, even in the configuration of the composite slab, there is a problem that the wavefront of the laser light is disturbed by the three-dimensional temperature distribution or the stress distribution near the light input / output surface of the transparent slab medium at the center.

As a solid-state slab laser capable of solving the above-mentioned problems, there is a solid-state laser using two slab-shaped laser media disclosed in Japanese Patent Application Laid-Open No. 4-30484 shown in FIG. This solid-state laser excites the laser medium along the zigzag optical path of the oscillating laser light 1220 formed inside the two laser mediums 1210 and the portion sandwiched between the two laser mediums 1210 by the resonator. Individual semiconductor lasers having directivity and high output power density are arranged and used as the excitation light source 1230.

[0011]

In the above-mentioned apparatus using the conventional solid-state slab laser, the output light of the individual pumping semiconductor laser having a large output power density is incident on the laser medium along a zigzag optical path to oscillate the internal laser. Exciting laser light. However, since the excitation laser light is transmitted only once through the laser medium for excitation, the efficiency of absorption of the excitation light by the slab laser medium is low, so that there is a problem that it is not possible to obtain a large output. In order to solve this problem, when a plurality of pumping semiconductor lasers are provided, there is a problem that economic efficiency is deteriorated. Further, the use of a plurality of pumping semiconductor lasers requires cooling of the slab laser medium. However, the above-mentioned structure does not disclose a forced cooling mechanism of the slab laser medium by a fluid or the like. There is a practical problem that it is impossible.

An object of the present invention is to provide a low-cost, high-performance solid-state slab laser device which can stably realize high quality, high output, and output variability by solving such problems. is there.

[0013]

A solid slab laser device according to the present invention has a longitudinal direction in which a generated laser beam travels in a zigzag optical path, and forms a parallel line in a plane perpendicular to the longitudinal direction. A laser medium comprising two slab-shaped laser media disposed opposite to each other with a space therebetween, and a fixture for fixing the laser medium at a predetermined position, wherein the laser medium faces the central space and a first optical thin film is provided. An inner surface to be coated and an outer surface opposite to the central space and coated with a second optical thin film, and the excitation light passes through the inside of the two slab-shaped laser media and the laser medium The laser light that excites the inside and oscillates is selectively totally reflected by the second optical thin film on the inner surface of the outer surface, and is transmitted without reflection by the first optical thin film on the inner surface, The outside In the inside to form the zigzag optical path through the said slab-shaped laser medium said central space alternately.

As described above, since the excitation light can pass through both of the two opposing slab-shaped laser media over the entire surface and can be excited, an excitation light source having a shape suitable for this can be used. Accordingly, since it is not necessary to locally concentrate the output of the pumping light, it is possible to eliminate the need for a high-output pumping laser light source which has a large output power density and thus has a long life.

Further, in the solid-state slab laser device according to the present invention, it is preferable that an inner surface of a portion including the fixing tool and forming the central space is a mirror surface reflecting 90% or more of the excitation light. With such a mirror surface, the excitation light can be confined in the internal space of the fixture for fixing the laser medium, and the excitation light can be used effectively.

Further, the fixture has an airtight member through which laser light can pass, at each of an entrance and an exit of the laser beam, to form the central space hermetically, and the laser medium has a predetermined flow rate and pressure. It is preferable to further include a gas introduction path for introducing a gas for correcting the shape of the gas into the central space. By introducing such a gas, it is possible to prevent the shape of the laser medium from being deformed when the cooling fluid flows on the outer wall surface of the laser medium.

The side surfaces of the two slab-shaped laser media may be arranged at a predetermined angle in the longitudinal direction, or may be formed by the two parallel slab-shaped laser media. Preferably, a prism is provided at an end of the central space where the laser light enters and exits, and an optical axis of the laser light entering and exiting is parallel to a side surface of the laser medium. The direction of the laser beam can be adjusted by the prism.

In one specific solid-state slab laser device according to the present invention, the laser medium is disposed so as to oppose the central space and an inner surface on which an optical thin film is coated and the central space are disposed. Has an outer surface on the opposite side to which excitation light is irradiated from the outside as an excitation surface, and the excitation light passes through the inner and outer surfaces of the two slab-shaped laser media to excite the inside of the laser medium.

In this apparatus, a reflection surface is provided on the surface for emitting the excitation light, excluding an excitation light source portion for emitting the excitation light, for reflecting the excitation light arriving through the two laser media. An inner wall surface surrounding the optical path of the excitation light between the reflecting surface and the outer surface of the laser medium through which the excitation light is transmitted, the inner wall surface including the fixture and reflecting the internal excitation light; Further comprising a transparent member provided with a predetermined gap to the outside surface of the device and transmitting the excitation light, wherein the reflection surface and the inner wall surface form a light condensing surface for condensing the internal excitation light on the outside surface. Is desirable. As a result, the excitation light can pass through the laser medium a plurality of times, and the laser medium can be effectively excited.

Further, in another solid-state slab laser device according to the present invention, the laser medium is opposed to the central space, and an inner surface on which a first optical thin film is coated and an opposite surface to the central space. And an outer surface on which a second optical thin film is coated, and the excitation light is perpendicular to the longitudinal direction from the widthwise end faces of the two laser media and is incident parallel to the side surface of the laser medium. Then, the total reflection is repeated on both side surfaces of each of the laser media to excite the inside. As described above, since the excitation light is incident on the entire inside of each of the two laser media, a normal output excitation light source having a structure suitable for this can be used. Therefore, it is possible to eliminate the need for a high-output excitation laser light source that has a large output power density as the excitation light and thus has a long life.

Further, it is preferable that a cooling fluid flows in a predetermined direction by using a gap formed between the transparent member and the outer surface or a gap in contact with the outer surface of the laser medium as a fluid path. As a result, the thin slab-shaped laser medium can be efficiently cooled.

In order to cool and control the temperature of the laser medium from the inner surface, one or a plurality of fixtures for the laser medium may be provided in the center of the space between the laser media in the laser traveling direction, which is the longitudinal direction, or along the longitudinal direction. It is desirable to provide a plurality of gas introduction paths and discharge paths, and to flow the cooling gas perpendicular to the longitudinal direction and parallel to the side surface of the slab-shaped laser medium.

[0023]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a side view showing one mode of using a slab-shaped laser medium used in the present invention.

In a solid-state slab laser using the laser medium 10 shown in FIG. 1, two laser media 10 have the same length L ₀ and thickness d ₀ parallel to each other and have a length L in the longitudinal direction.
_The center space 1 is maintained while maintaining the same interval d ₁ at a position shifted by 1
1 are formed. Each of the two laser media 10 has an outer surface 12 and a central space 11 opposite to the central space 11.
, Each having an inner side surface 13 facing and facing.

As shown in the figure, a laser beam 20 of a beam having a diameter D is incident on the surface of the laser medium 10 at an incident angle θ with the optical axis of the laser beam placed in a plane perpendicular to the surface of the laser medium 10. It is assumed that the incident light is Laser medium 1
0 has an anti-reflection coating that does not reflect the incident laser light 20. On the other hand, the outer surface 12 totally reflects the incident laser light 20 to the inner side by the total reflection coating. Laser light incident from one end exits through an optical path having an angle symmetric to the angle incident from the other end. Accordingly, the length L ₁ of the shift two laser medium 10 is located is represented by Equation 1 below.

[0027]

(Equation 1)

That is, when the beam of the laser beam 20 is turned over the entire outer surface 12 of the laser medium 10 without any gap, the condition is such that the laser beam 20 having the beam diameter D is in a plane perpendicular to the surface of the laser medium 10. When incident at an incident angle θ, the refractive index n of the slab-shaped laser medium 10 and the number of times the laser light 20 is folded back over the entire surface of the outer surface 12 without any gap is an arbitrary integer N equal to or greater than “1”, and the beam diameter D And the total length L ₀ of the laser medium 10 are represented by the following Expressions 2 and 3.

[0029]

(Equation 2)

(Equation 3)

Here, when the slab medium is an Nd: YAG crystal, since n = 1.82, d ₀ = 1.5 mm
And d ₁ = 5.3 mm, by choosing N = 3, L ₀ = 15 mm, incident angle θ = 70 degrees, and D =
4.2 mm can be determined. Under these conditions, efficient amplification can be achieved by matching the dimension of the slab medium 10 in the width direction with the beam diameter D of the laser beam.

Next, a solid slab laser device according to the present invention will be described with reference to FIG. FIG. 2 is an explanatory cross-sectional view showing a cross-section when the longitudinal direction of the laser medium 110 is a direction perpendicular to the sheet of paper as one embodiment of the present invention.

The solid-state slab laser device shown in FIG.
In the central portion, two laser media 110 having the shape shown in FIG. 1 and a structure in which the two laser media 110 are positioned substantially parallel and opposed to each other as shown in FIG. Fixture 1 forming a certain central space 111
40, and two transparent members 150 arranged at a predetermined gap along the outside of the outer surface of each of the two laser media 110. Excitation light 130 for exciting the laser medium 110 irradiates substantially the entire outer surface of the laser medium 110 from outside the two transparent members 150 disposed outside each of the laser medium 110.

The fixture 140 uses the inner surface forming the central space 111 as a mirror surface 141 to confine the excitation light 130 in the central space 111 by reflection, and converts the excitation light 130 incident from the outside into the laser light 120 inside the laser medium 110. And the laser beam 120 is transmitted through the central space 111, and again within the laser medium 110 at the opposing position.
And can be emitted from the outer surface. For efficient confinement of the excitation light 130, it is desirable that the mirror surface 141 reflects 90% or more of the excitation light.

The fixture 140 is provided in the central space 111.
Each of the entrance and exit of the laser beam 120 at both ends has a hermetic member through which the laser beam 120 can pass to form a central space 111 in an airtight manner, and corrects the shape of the laser medium 110 with a predetermined flow rate and pressure. A gas introduction path 142 for introducing the gas to be introduced into the central space 111 is provided. Further, a gap formed between the outer surface of the laser medium 110 and the transparent member 150 disposed outside the laser medium 110 is provided as a fluid path 143 through which a cooling fluid flows in a predetermined direction.

Further, the fixing member 140 includes two transparent members 1.
An excitation light source 131 that emits the excitation light 130 that irradiates almost the entire outer surface of the laser medium 110 from the outside of the laser medium 110 has a confinement portion 145 for the excitation light 130 that holds the excitation light 130 on the outer facing surface of the laser medium 110. Almost the entire area of the confinement section 145 is occupied by the transparent member 150.

The transparent member 150 transmits the excitation light 130 emitted from the excitation light source 131 and radiates it from the transmission surface 151 facing the outer surface of the laser medium.

The transparent member 150 is coated with a metal thin film except for the portion of the excitation light source 131 that emits the excitation light 130, and reflects the excitation light transmitted through the outer surface of the laser medium and reflects the excitation light. An intermediate wall surface 153 which is formed between the surface 152 and the outer surface of the laser medium 110 so as to surround the optical path of the excitation light 130, is coated with a metal thin film, and is a mirror surface which reflects the internal excitation light; 152 and the intermediate wall surface 153 form a light-collecting surface that focuses the internal excitation light 130 on the outer surface of the laser medium 110.

The central space 111 can be filled with a gas such as air or helium gas and sealed.
The slab-shaped laser medium 110 can be cooled by flowing gas using the gas introduction path 142. Furthermore,
In a fluid path 143 formed between the outer surface of the laser medium 110 and the transparent member 150, a cooling fluid is provided in the longitudinal direction or the width direction of the laser medium 110 in a direction perpendicular to the surface of the zigzag optical path of the laser light 120. The flowing laser medium 110 is cooled. The slab-shaped laser medium 110 may be mechanically deformed by the pressure of the cooling fluid. If the laser medium 110 has a curvature, the gas pressure value in the central space 111 is controlled. Can be adjusted externally to compensate for mechanical deformation.

The excitation light 13 emitted from the excitation light source 131
0 excites the laser medium 110 by transmitting through the transparent member 150 and entering the inside of the laser medium 110 from almost the entire outer surface that is the excitation surface. Therefore, it is desirable that the outer surface of the laser medium 110 and the transmission surface 151 of the transparent member 150 are coated with an anti-reflection coating that does not reflect excitation light. The excitation light 130 emitted from the excitation light source 131
In order to efficiently reach the laser medium 110, the light-collecting surface formed by the reflection surface 152 and the intermediate wall surface 153 of the transparent member 150 guides the excitation light 130. Further, the excitation light 130 transmitted through the laser medium 110 is confined in the central space 111 by the mirror surface 141 forming the central space 111 and guided to the other laser medium 110.

Therefore, the excitation light 130 passes through the second laser medium 110 on the opposite side from the one laser medium 110 via the central space 111, and furthermore, is reflected by the reflection surface 152 and the intermediate wall surface 153 of the transparent member 150. The laser light 120 is reflected by the formed condensing surface, turned back again, and added to the excitation light 130 newly emitted from the excitation light source and transmitted through the third laser medium 110, which has become the second, to excite the laser light 120. can do.

As the excitation light 130, a one-dimensional semiconductor laser array can be used. Further, by arranging the two-dimensional semiconductor laser array at the position of the reflection surface 152 which is a part of the light-collecting surface, higher excitation intensity can be obtained.

Next, a solid slab laser device according to the present invention, which is different from FIG. 2, will be described with reference to FIG. FIG.
FIG. 1 is an explanatory cross-sectional view showing a cross section when a longitudinal direction of a laser medium 110 is a direction perpendicular to a paper surface as one embodiment of the present invention.

The solid slab laser device shown in FIG. 3 differs from that of FIG. 2 in that a predetermined gap is provided along the outer surface of each of the two laser media 110 instead of the transparent member 150 of FIG. That is, two transparent members 160 each having a flat plate shape are provided. Therefore,
Except for the excitation light source 131 that emits the excitation light 130, the confinement unit 145 includes a reflection surface 146 that reflects the excitation light that is transmitted through the outer surface of the laser medium and that transmits the reflection surface 146 and the excitation light 130. An intermediate wall surface 147 which is a mirror surface formed around the optical path of the excitation light 130 between itself and the surface of the transparent member 150 to reflect the excitation light therein.
The reflecting surface 146 and the intermediate wall surface 147 form a condensing surface that condenses the internal excitation light 130 on the outer surface of the laser medium 110. That is, in order for the excitation light 130 emitted from the excitation light source 131 to efficiently reach the laser medium 110, the reflection surface 146 of the confinement unit 145 and the intermediate wall surface 1
The light-collecting surface formed by the light-guiding surface 47 guides the excitation light 130.

Except for the differences described above, the configuration is the same as that of FIG. 2, and the same reference numerals are given to the components, and the description thereof will be omitted.

Next, a solid slab laser device different from FIG. 2 or FIG. 3 will be described with reference to FIG. FIG.
As another embodiment of the present invention, the laser medium 21
It is explanatory sectional drawing which shows the cross section when the longitudinal direction of 0 is made into a perpendicular direction with respect to a paper surface.

The solid-state slab laser device shown in FIG.
In the central portion, two laser media 210 having the shape shown in FIG. 1 and a structure in which the two laser media 210 are positioned substantially parallel and opposed to each other as shown in FIG. Fixture 2 forming a certain central space 211
40. Excitation light 230 that excites the laser medium 210 irradiates substantially the entire area of both sides of the slab-shaped laser medium 210 that is thin in the width direction perpendicular to the longitudinal direction.

Therefore, the excitation light 230 is confined inside by repeating total reflection on the inner wall surface of the slab-shaped laser medium 210, and can excite the laser medium 210 efficiently. Further, it is preferable that the inner wall surface of the fixture 240 facing the central space 211 be a mirror surface 241 and the excitation light 230 leaking into the central space 211 be confined and guided to the laser medium 210 on the other side.

The center space 211 can be filled with a gas such as air or helium gas and sealed in the same manner as described with reference to FIG. 2, but the slab-shaped laser medium is formed by flowing the gas through the gas introduction passage 242. 210 can be cooled.

Further, the fixture 240 is provided on the fluid path 243 formed on the outer surface of each of the two slab-shaped laser media 210 in a direction perpendicular to the plane of the zigzag optical path of the laser light 220. A cooling fluid flows in the longitudinal direction or the width direction to cool the laser medium 210. Due to the pressure of the cooling fluid, the slab-shaped laser medium 21
0 may be mechanically deformed, but the laser medium 2
In the case where 10 has a curvature, it can be adjusted from the outside so as to control the gas pressure value in the central space 211 to compensate for the mechanical deformation.

As the excitation light 230, a one-dimensional semiconductor laser array can be used as described above.

Next, a description will be given of a solid slab laser device in which the arrangement of the laser medium is different from that described above with reference to FIG. FIG. 5 is an explanatory side view showing a side surface when the width direction of the laser medium 310 is a direction perpendicular to the paper surface as another embodiment of the present invention.

In contrast to the above-described ones arranged and incorporated in parallel with each other, the two slab-shaped laser media 310 shown in FIG. 5 are parallel in the cross section in the width direction, but are parallel in the cross section in the longitudinal direction. It is arranged with the inclination angle theta _1.

Because of this inclination, the incident laser beam 32
Numeral 0 reflects the inside and inner space 311 of the slab-shaped laser medium 310 many times to form a zigzag optical path and return to the incident side. Two slab-shaped laser media 31
Since 0 has the inner space 311, it is easy to adjust the size of the inclination angle θ ₁ . In addition, laser light 3
A total reflection mirror 312 and an output mirror 313 of the laser beam 320 are provided for exciting, amplifying, and emitting the light 20.

Next, a solid slab laser device in which optical prisms are provided at both ends of the above-mentioned two slab-shaped laser media will be described with reference to FIG.

As shown in FIG. 6, a prism 412 for closing a slope of an opening formed at an end of a central space 411 in the longitudinal direction of two slab-shaped laser media 410 is provided.
It has the same cross-sectional shape as the central space 411, and the slope on the opposite side to the central space 411 is a slab-shaped laser medium 41.
The angle of the laser beam 420 incident parallel to the plane 0 is such that the beam can be reflected many times inside the prism 412, inside the laser medium 310 and inside space 311 to form a zigzag optical path. Therefore, it is possible to adjust the beam direction by disposing the prisms 412 at both ends of the central space 411 formed by the laser medium 410, that is, at the entrance and exit of the laser light 420.

In the solid-state slab laser device described in FIGS. 2 to 6, two slab-shaped laser media as shown in FIG. 1 are employed. Accordingly, by adjusting the distance between the two slab-shaped media, that is, the thickness of the central space, it is possible to sufficiently secure the overlap of the mode volumes even in the oscillation of the low-order mode laser light. On the other hand, the thickness of each slab medium can be freely selected independently of the mode diameter of the beam. Therefore, by increasing the aspect ratio of the slab medium, it is possible to improve the cooling efficiency of the slab and to provide a high excitation input.

Further, since there is a hollow portion along the laser light path, a slab formed near the laser light input / output surface of the slab alone can be used.
The disturbance of the laser wavefront due to the dimensional temperature distribution and stress distribution or the thermal birefringence and thermal lens effect in the zigzag optical path do not occur except in the thin slab medium. Further, there is no problem that the wavefront of the laser light is disturbed by the three-dimensional temperature distribution or stress distribution generated near the laser light input / output surface of the slab alone. Therefore, an apparatus capable of stably outputting the same high-quality beam as in the case of a low excitation input even under a high excitation input can be easily realized.

Further, the solid slab laser device according to the present invention has a structure that can be mechanically assembled as compared with a composite slab type synthesized by high-temperature fusion under precise temperature control. Can be easily realized, and a low-cost and high-output laser beam can be easily obtained.

[0059]

As described above, according to the present invention, it is possible to provide a low-cost, high-performance solid-state slab laser device capable of easily realizing high quality, high output, and stable output variability. .

First, since the structure is mechanically assembled, a slab medium having a long dimension can form a hollow solid slab laser with a space therebetween, and therefore, inexpensive and high-power laser light can be easily produced. Obtainable.

Second, since the excitation light is confined in the slab medium by providing a mirror surface around the slab medium or directly entering the slab medium so as to be totally reflected inside, the excitation efficiency of the slab medium can be kept high. Therefore, high output can be obtained at low cost.

Third, since a structure in which the surface of the slab medium is directly cooled by a fluid can be easily realized, the slab medium operates stably without deteriorating the beam quality even with a high excitation input. The output can be obtained easily at a low price.

[Brief description of the drawings]

FIG. 1 is a side view showing one mode of use of a slab-shaped laser medium used in the present invention.

FIG. 2 is an explanatory transverse sectional view showing one embodiment of a sectional structure in the present invention.

FIG. 3 is an explanatory cross-sectional view showing one embodiment of a cross-sectional structure different from that of FIG. 2;

FIG. 4 is an explanatory cross-sectional view showing one embodiment of a cross-sectional structure different from those of FIGS.

FIG. 5 is a side view showing an embodiment of a slab-shaped laser medium arrangement different from that of FIG. 2-4.

FIG. 6 is a side view showing an embodiment in which an optical prism is arranged at an end of the slab-shaped laser medium in FIG. 2-4.

7A and 7B are a side view (A) and a plan view (B) when a conventional slab-shaped laser medium is a solid-state laser.

FIG. 8 is an explanatory side view in the case where two conventional slab-shaped laser media have a composite structure.

FIG. 9 is a side view showing an example in which a space is provided between two conventional slab-shaped laser media and provided.

[Explanation of symbols]

 10, 110, 210, 310, 410 Laser medium 11, 111, 211, 411 Central space 12 Outer surface 13 Inner surface 20, 120, 220, 320, 420 Laser light 130, 230 Excitation light 131, 231 Excitation light source 140, 240 Fixture 141, 241 Mirror surface 142, 242 Gas introduction path 143, 243 Fluid path 145 Enclosure 146, 152 Reflection surface 147, 153 Intermediate wall surface 150, 160 Transparent member 151 Transmission surface 311 Inner space 412 Prism

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeshi Yamane 5-7-1 Shiba, Minato-ku, Tokyo F-term within NEC Corporation 5F072 AB02 AK04 FF03 JJ04 JJ05 KK05 KK30 PP07 TT01 TT16

Claims (11)

[Claims] 1. A longitudinal direction in which a generated laser beam travels in a zigzag optical path, and two slab-shaped slabs which are arranged to face each other across a central space in a plane parallel to a plane perpendicular to the longitudinal direction. A laser medium, and a fixture for fixing the laser medium in a predetermined position, wherein the laser medium is opposed to the central space and has an inner surface on which a first optical thin film is coated and is opposite to the central space. And an outer surface coated with a second optical thin film, the excitation light passes through the inside of the two slab-shaped laser media to excite the inside of the laser medium, and the laser light The second inside
Is totally reflected by the optical thin film, and passes through the inner optical surface without reflection by the first optical thin film, so that the slab-shaped laser medium and the central space alternately pass through the inner surface of the outer surface. Forming a zigzag optical path as described above. 2. The solid-state slab laser device according to claim 1, wherein an inner surface of a portion including the fixture and forming the central space has a mirror surface that reflects 90% or more of the excitation light. 3. The fixing device according to claim 1, wherein the fixture has an airtight member through which the laser light can pass, at each of an entrance and an exit of the laser light, so that the central space is airtightly formed. The solid-state slab laser device further comprises a gas introduction path for introducing a gas for correcting the shape of the laser medium with a pressure into the central space. 4. The solid-state slab laser device according to claim 1, wherein the side surfaces of the two slab-shaped laser media are arranged at a predetermined angle in the longitudinal direction. 5. The laser beam according to claim 1, wherein the laser beam is provided at an end where laser light enters and exits in the central space formed by the two parallel slab-shaped laser media. A solid-state slab laser device, further comprising a prism having an optical axis parallel to a side surface of the laser medium. 6. The laser device according to claim 1, wherein the laser medium is disposed to face the center space, and an inner surface on which the first optical thin film is coated is opposite to the center space. A solid-state slab laser device, wherein the excitation light passes through the inner and outer surfaces of the two slab-shaped laser media to excite the inside of the laser medium. 7. The metal thin film according to claim 6, wherein the metal thin film is located on a surface for emitting the excitation light and reflects the excitation light arriving through the two laser media except for an excitation light source portion for emitting the excitation light. A reflective surface coated with, and a metal thin film formed around the optical path of the excitation light between the reflection surface and the outer surface of the laser medium through which the excitation light passes and reflecting the internal excitation light. A transparent member having a coated intermediate wall surface and a transmission surface that faces the outer surface of the laser medium with a predetermined gap and transmits the excitation light, wherein the reflection surface and the intermediate wall surface have internal excitation light. A solid-state slab laser device, which forms a light-collecting surface for collecting light on the outer surface. 8. The apparatus according to claim 6, excluding a plate-shaped transparent member opposed to the outer surface of the laser medium with a predetermined gap, and an excitation light source portion on the surface for emitting the excitation light and emitting the excitation light. A reflection surface that reflects the excitation light arriving through the two laser media and a transparent member that transmits the excitation light and surrounds an optical path of the excitation light between the reflection surface and the transparent member that transmits the excitation light. A solid slab laser device, further comprising an intermediate wall surface for reflecting the internal excitation light, wherein the reflection surface and the intermediate wall form a condensing surface for condensing the internal excitation light on the outer surface. . 9. The solid slab according to claim 7, wherein a gap formed between the transparent member and the outer surface is a fluid passage for flowing a cooling fluid in a predetermined direction. Laser device. 10. The laser medium according to claim 1, wherein the laser medium faces the central space and an inner surface on which a first optical thin film is coated is opposite to the central space.
An outer surface on which an optical thin film is coated, and the excitation light is perpendicular to the longitudinal direction from the widthwise end face of each of the two laser media, and is incident parallel to the side surface of the laser medium to emit laser light. A solid-state slab laser device wherein the inside is excited by repeating total reflection on both side surfaces of each medium. 11. The solid-state slab laser device according to claim 10, further comprising a fluid path in contact with an outer surface of said laser medium and flowing a cooling fluid in a predetermined direction.