JPH0569963U - Solid-state laser medium and solid-state laser device using the same - Google Patents

Abstract

(57) [Abstract] [Purpose] To reduce the loss of pumping light due to the increase in output of laser light and to improve the oscillation efficiency. The optical contact surface 1B of a plurality of Nd: YAG rod pieces 1A arranged in the optical axis direction is fused to form a long solid laser medium. In this medium, the temperature of the optical contact surface 1B is raised at a constant rate (for example, 2 ° C./minute) by using an electric furnace,
Then, the temperature is maintained at a temperature sufficient for fusion bonding (for example, 920 ° C.) and heating is performed for a certain period of time (for example, 20 hours) to perform fusion bonding, and then, a constant rate (for example, 1 ° C.) that is a cooling rate capable of removing thermal stress. C / min) to form. This long N
A laser device is formed using the d: YAG rod 1. By using the long Nd: YAG rod 1, a large output laser beam can be easily output.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a high-power solid-state laser medium used for metal processing and the like, and a solid-state laser device using the same, and more particularly to a solid-state laser medium with improved oscillation efficiency and simplification of the device, and a solid-state laser using the same. Regarding the device.

[0002]

[Prior Art]

 As a solid-state laser device, a device as shown in FIG. 5 is generally known. FIG. 5 is a schematic perspective view showing the structure of an apparatus including an Nd: YAG laser and a resonator.

In the figure, reference numeral 501 is an Nd: YAG rod, reference numeral 502 is a lamp that is an excitation light source, and 503 is a reflector that efficiently collects the light emitted from the excitation light source on the Nd: YAG rod. In addition to these, a cooling device (not shown) for cooling the Nd: YAG rod 501, the lamp 502, and the reflector 503 with water, a high-voltage power supply device for supplying power to the lamp 502, and a laser resonator are configured. An output mirror and a total reflection mirror are attached.

The laser output obtained by this laser device has an upper limit of 400 to 600 W, although it depends on the size of the Nd: YAG rod 501.

On the other hand, in the current Nd: YAG crystal growth technique, the upper limit of the crystal length is about 20 cm. Therefore, when a high-power laser beam is required, a plurality of laser devices shown in FIG. A multi-stage laser device (for example, LAY-657B manufactured by Toshiba Corp. in four-stage series connection) connected in series in the axial direction through a space is used.

[0006]

[Problems to be solved by the device]

 However, in the conventional multi-stage laser device described above, the excitation light is likely to leak outside the reflector 503 at both ends of the Nd: YAG rod 501 due to its structure. Further, the reflection of the excitation light cannot be expected at the electrode portion of the lamp 502. Furthermore, since the ends of these rods and the lamp electrode part increase in proportion to the number of connections of the laser device, the loss of pumping light in these parts also increases in proportion to the number of connections.

In order to solve this problem and improve the excitation efficiency and uniform the excitation distribution, a laser device using a diffuse reflection type reflector such as a white ceramic having a high reflectance from the near-ultraviolet to the infrared range. May be used. In this case, however, the cross-sectional shape of the reflector (the shape in the direction perpendicular to the optical axis) is not the elliptical shape that secures a sufficient space as in the above-mentioned configuration, but is the diffuse reflection type so that the laser rod and the lamp should be as close as possible. The reflectors are also shaped so as to be close to them and have a small surface area. That is, since the cross-sectional shape of the reflector is small, the ratio of the loss of the excitation light at both ends of the rod and the lamp electrode portion becomes larger.

That is, the current multi-stage laser device has a problem that the loss of pumping light increases in accordance with the number of devices to be multi-staged, resulting in poor pumping efficiency.

Further, in the case of a slab laser device using a crystal such as Nd: YAG, the slab end face shape is finished into a slope of about 30 degrees (Brewster angle), and further O is used for sealing inside the device. Since sealing parts such as rings are assembled, it becomes impossible to excite within a certain distance from the both ends of the slab (distance about 3 to 4 times the thickness of the slab). This is a slab-specific problem that does not pose a problem in the rod type without the Brewster end face. For example, in the case of an Nd: YAG slab having a length of 150 mm and a thickness of 6 mm, a portion of about 24 mm on one side and about 48 mm on both sides from the end of the slab cannot be excited. Although the Nd 3: YAG crystal is expensive, in this example, only 2/3 of the total length of the slab directly affects the laser oscillation in this example. For example, in the example shown in Japanese Examined Patent Publication No. 2-331513, "Plane pump type rectangular thick plate laser device with optical resonance cavity", the slab has a total length of about 139.4 mm and a thickness of about 8 mm. It is estimated that about 32 mm on one side and about 64 mm on both sides from the end of can not be excited. Therefore, in this thick plate laser device, the excited portion is considered to be about half of the entire length of the slab.

On the other hand, if the thickness of the slab is reduced in order to reduce the portion that cannot be excited, the excitation light that passes through the slab increases and the excitation efficiency decreases. For this reason, the thickness of the current Nd: YAG slab is at least about 5 to 6 mm, although it depends on the size of the slab.

For the above reasons, there is nothing but increasing the total length of the slab in order to reduce the unexcitable part and improve the ratio of the exciting part to the total length of the slab. However, in the current Nd: YAG crystal growth technique, the upper limit of the crystal length is about 20 cm under the present circumstances.

As one of the features of the slab laser, it is known that the zigzag optical path inside the slab cancels the influence of the heat inside the slab due to the pumping. At times, wavefront distortion due to thermal distortion occurs. It is known that the main cause is thermal stress near the Brewster end face (for details, refer to the document `` Thomas J. Kane, John M. Eggleston, Robert L. Byer, IEEE Journal of Quantum Electron ics, vol. QE-21, No.8, 1195, August 1985, The Slab Geometry Laser-Part II: Thermal Effects in a Finite Slab ").

Therefore, when trying to obtain a high-power laser beam by connecting the slab laser devices in multiple stages, the number of Brewster end faces increases. As a result, there is a problem that the beam quality such as the condensing property of the laser light is deteriorated.

The present invention has been made in view of the above problems, and an object of the present invention is to integrally fuse a plurality of rods or slabs, and to provide a large number of end portions of the rod and the lamp electrode portion that cause a large loss of excitation light. It is an object of the present invention to provide a high-output solid-state laser medium with high efficiency and a solid-state laser device using the same.

[0015]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, the solid-state laser medium according to the present invention comprises a plurality of solid-state laser medium pieces arranged in the optical axis direction, and their optical contact surfaces are fused to form a long length.

It is preferable that the solid-state laser medium is heated and fused to a temperature sufficient to fuse the optical contact surface.

A solid-state laser device according to the present invention uses the long solid laser medium as the solid-state laser medium.

[0018]

[Action]

 By forming the solid-state laser medium in a long size as described above, a high-power laser beam can be easily produced.

By heating fusion of a plurality of solid laser medium pieces at a constant rate up to a temperature sufficient for the fusion and continuing heating at the temperature for a certain period of time, a solid laser with less optical loss is produced. A medium can be formed.

Further, by using the long solid laser medium as the solid laser medium of the solid state laser device, a connection is made in a case where short solid state laser mediums are connected in multiple stages in order to increase the output as in the conventional case. There is no loss in parts. For this reason, it is possible to reduce the loss of the excitation light due to the increase in the output and to improve the efficiency. In addition, the device can be configured with a small number of parts, and the manufacturing cost can be reduced and the reliability can be improved.

[0021]

【Example】

 Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic perspective view showing a main part of a solid-state laser device according to a first embodiment of the present invention. This solid-state laser device uses an Nd: YAG laser as a long solid-state laser medium.

Reference numeral 1 in the drawing is a long Nd: YAG rod formed by fusing a plurality of Nd: YAG rod pieces 1A as solid-state laser medium pieces in the optical axis direction by using a fusion technique described later. Reference numeral 2 denotes a lamp which is an excitation light source, and 3 denotes a reflector for efficiently collecting the light emitted from the excitation light source on the Nd: YAG rod 1. Reference numeral 4 is a plane output mirror, and reference numeral 5 is a convex total reflection mirror. Further, in addition to this, a structure or enclosure for fixing each component (not shown), a pure water cooling device for cooling the Nd: YAG rod 1, the lamp 2, and the reflector 3 with water, a high-voltage power supply for supplying power to the lamp 2. The equipment, Nd: YAG rod 1 and glass flow tube for uniformly cooling the lamp 2 are attached. Reference numeral 6 denotes a laser beam oscillated between the plane output mirror 4 and the convex total reflection mirror 5.

In this embodiment, the Nd: YAG rod 1 is formed by elongating two Nd: YAG rod pieces 1A in the optical axis direction. Then, the fusion of each Nd: YAG rod piece 1A is performed by the fusion technique described in JP-A-2-153849. This fusion technology is specifically as follows.

Optical contact (optical contact) is made between two Nd: YAG rod pieces 1A at their end surfaces (optical contact surface 1B), and the optical contact surface 1B is heated at a constant heating rate using an electric furnace to obtain a temperature. Raise. Next, after heating the optical contact surface 1B to a temperature sufficient for fusing, the temperature is maintained for a certain period of time. As a result, the optical contact surface 1 B is fused, and then the optical contact surface 1 B is cooled at a cooling rate that can eliminate the generation of thermal stress in the fused portion.

Next, the solid-state laser device will be described by raising specific numerical values.

First, the fusion of the Nd: YAG rod 1 is performed as follows. The Nd: YAG rod piece 1A (Nd doping amount 1.0 atom%) is formed to have a length of 110 mm and a diameter of 10 mm. Two Nd: YAG rod pieces 1A are brought into optical contact at their optical contact surfaces 1B, and heated by raising the temperature at a rate of 2 ° C / min using an electric furnace. At this time, the two Nd: YAG rod pieces 1A are heated while being pressed together by a pressing device (not shown) in order to pressurize the optical contact surface 1B and promote fusion. .. Next, the temperature is raised to a temperature of 920 ° C., which is a sufficient temperature for fusing the optical contact surface 1B, and the temperature is maintained for 20 hours. After that, it is cooled at a cooling rate of 1 ° C./min, which is capable of removing the thermal stress.

As the lamp 2, a krypton lamp (manufactured by ILC, USA, model number 10F8) having a light emission length of about 200 mm and an inner diameter of 10 mm is used. As the reflector 3, in order to collect the light emitted from the excitation light source to the Nd: YAG rod 1 efficiently, a reflector made of white ceramic (trade name: Macerite manufactured by Mitsui Mining Co., Ltd.) is used. The reflector 3 may be a gold vapor deposition reflector. A mirror having a reflectance of 75% is used as the plane output mirror 4, and a mirror having a curvature of 2 m is used as the convex total reflection mirror 5. The resonator length is 400 mm. The pure water cooling device has a cooling capacity of about 25 kW and a pure water flow rate of about 40 liters per minute.

In the solid-state laser device having the above configuration, a laser output of about 800 W was obtained for an electric input of 19 kW during multimode oscillation. At this time, the efficiency (laser output / electric input) was 4.2%. The efficiency of the solid-state laser device using the long fused Nd: YAG rod 1 of the present invention is very high, compared with the efficiency of the conventional multi-stage laser device of about 2.5 to 3%. I understand.

On the other hand, it is a well-known fact that most of the manufacturing cost of a solid-state laser device is a power supply unit. For this reason, the higher the laser output is, the higher the oscillation efficiency becomes. For example, in the conventional multi-stage laser device, in order to obtain a laser output of 1 kW, the efficiency is about 3%, so that the output of the laser power supply is required to be at least about 33.4 kW.

On the other hand, in the solid-state laser device of this embodiment, if an efficiency of 4.2% is obtained when a laser output of 1 kW is to be obtained, the output of the laser power supply is about 23.8 kW. Becomes Therefore, the same 1 kW can be generated by the laser power supply having the output of about 71% as compared with the conventional laser device having the efficiency of 3%.

As is clear from the above description, according to the solid-state laser device using the Nd: YAG rod 1 of the present embodiment, like the conventional multi-stage laser device, both ends of the rod and the lamp with large loss of pumping light are provided. It is possible to increase the output of the device without increasing the number of electrode parts, and it is possible to obtain higher oscillation efficiency.

Further, since the laser device is composed of a single Nd: YAG rod 1, the number of parts is reduced, and the cooling machine power source is reduced due to the reduction of cooling targets, and the cooling machine volume is also reduced. Therefore, the manufacturing cost of the chiller is significantly reduced. Also, the output of the laser power supply can be reduced as described above. That is, if the efficiency of laser oscillation is high, the device is downsized, the manufacturing cost is low, and the amount of electricity used during operation is low. Furthermore, the number of consumable lamps 2 does not increase, which leads to a reduction in working time when replacing the lamps. For these reasons, the manufacturing cost and running cost can be significantly reduced, and the reliability of the laser device is improved.

In the present embodiment, the case where two Nd: YAG rod pieces 1A having the same length are fusion-bonded as the Nd: YAG rod 1 has been described as an example. The strips 1A do not necessarily have the same length, and the number of fused pieces is not limited to two. That is, the length of the Nd: YAG rod 1 differs depending on the set output value, and in order to make the rod 1 a length according to the set output value, a plurality of Nd: YAG rod pieces 1A having the same or different lengths are used. And adjust to the set length.

FIG. 2 shows a second embodiment of the present invention.

In this embodiment, a long Nd: YAG slab is used as the solid-state laser medium. In the figure, reference numeral 201 is a long Nd: YAG slab formed by fusing two Nd: YAG slab pieces 201A in the optical axis direction, reference numeral 202 is a lamp that is an excitation light source, and 203 is a reflector. Reference numeral 204 indicates laser light that is optically amplified by the Nd: YAG slab 201. The other structure is the same as that of the first embodiment.

The fusion means for the Nd: YAG slab piece 201A is based on the fusion technique described in the first embodiment. Further, various conditions such as the length of the Nd: YAG slab piece 201A are also applied in the same manner as the above-mentioned first embodiment. It should be noted that the optical axis direction referred to here is not a specific traveling direction of the laser light traveling in zigzag in the Nd: YAG slab 201, but a traveling direction of the laser light excited in the Nd: YAG slab 201 as a whole. That is, it means the longitudinal direction of each Nd: YAG slab piece 201A in FIG.

Also in the laser device having the above configuration, the same operation and effect as those of the first embodiment can be obtained.

Further, in the slab laser, the ratio of the excited portion to the entire length of the Nd: YAG slab 201 can be increased.

Furthermore, since the number of Brewster end faces, which are the causes of thermal distortion, is not increased, it is possible to achieve both higher output and improved beam quality such as the converging property of laser light.

FIG. 3 shows a third embodiment of the present invention.

In this embodiment, a long tubular Nd: YAG crystal is used as the solid laser medium. Reference numeral 301 in the drawing is a tubular Nd: YAG crystal formed by fusing two tubular Nd: YAG crystal pieces 301A in the optical axis direction to form a long tube, reference numeral 302 is a lamp as an excitation light source, and 303 is a reflector. Further, reference numeral 304 indicates a laser beam which is optically amplified by the tubular Nd: YAG crystal 301 and emitted in a circular shape. The other structure is the same as that of the first embodiment. The lamp 302 is inserted inside the tubular Nd: YAG crystal 301 so that the tubular Nd: YAG crystal 301 is irradiated with excitation light from the inside.

The means for fusing two tubular Nd: YAG crystal pieces 301A as the tubular Nd: YAG crystal 301 in the optical axis direction is based on the fusing technique of the first embodiment. Further, various conditions such as the length of the tubular Nd: Y AG crystal 301 are also applied as in the first embodiment.

Also in the laser device having the above configuration, the same operation and effect as those of the first embodiment can be obtained.

FIG. 4 shows a fourth embodiment of the present invention.

In this embodiment, a clad is provided on a long Nd: YAG rod as a solid-state laser medium. Reference numeral 401 in the figure is an Nd: YAG rod. A cladding layer 404 made of YAG crystal not doped with Nd is attached to the outer periphery of the Nd: YAG rod 401 by the fusion technique of the first embodiment in order to increase the excitation efficiency. The Nd: YAG rod 401 is formed by elongating two Nd: YAG rod pieces 401A to which the cladding layer 404 is attached in the optical axis direction by the fusion technique.

Reference numeral 402 is a lamp, and 403 is a reflector. Reference numeral 405 represents laser light optically amplified by the Nd: YAG rod 401. The other structure is the same as that of the first embodiment. Also, various conditions such as the length of the Nd: YAG rod piece 401A are applied in the same manner as in the first embodiment.

Also in the laser device having the above configuration, the same operation and effect as those of the first embodiment can be obtained.

Furthermore, since the cladding layer 404 is attached to the Nd: YAG rod piece 401A in this embodiment, the excitation efficiency can be further improved.

In each of the above embodiments, the case where the long solid laser medium is used as the oscillator has been described as an example, but the same operation and effect as described above can be obtained even when the solid laser medium is used as the amplifier.

Further, as the solid-state laser medium, in addition to the above-mentioned Nd: YAG crystal and the like, laser crystals such as GG, GSGG, YSGG, YSAG, YLF, alexandrite, and sapphire, and a phosphate laser glass (for example, HOYA. It is possible to use various laser glasses such as LHG-5, 8 manufactured by KK, silicate laser glass (for example, LSG-91H manufactured by HOYA).

Further, not only Nd but also Er, Cr, Ho, Tm and Ti may be used as the laser active ions. It is also possible to use different laser active ion doping amounts and types as required.

[0053]

[Effect of the device]

 As described above in detail, according to the present invention, since the solid-state laser medium is formed in a long size, it is not necessary to arrange a plurality of short-sized solid-state laser media in order to obtain a laser beam with a large output, and the connection thereof is eliminated. It is possible to eliminate the loss of the excitation light in the part.

Further, by using the long solid laser medium as the solid laser medium of the solid state laser device, the output of the device can be increased without increasing the number of both ends of the rod and the lamp electrode part where the loss of the excitation light is large. It becomes possible to obtain higher oscillation efficiency.

Further, since the number of parts of the laser device is reduced, the size and the power consumption are reduced, the manufacturing cost and the running cost can be significantly reduced, and the reliability of the laser device is improved.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing a main part of a solid-state laser device according to a first embodiment of the present invention using an Nd: YAG rod as a solid-state laser medium.

FIG. 2 is a schematic perspective view showing a main part of a solid-state laser device according to a second embodiment using an Nd: YAG slab as a solid-state laser medium.

FIG. 3 is a schematic perspective view showing a main part of a solid-state laser device according to a third embodiment using a tubular Nd: YAG crystal as a solid-state laser medium.

FIG. 4 Nd: Y with a clad layer as a solid-state laser medium
It is a schematic perspective view which shows the principal part of the solid-state laser apparatus which concerns on the 4th Example using an AG rod.

FIG. 5 is a schematic perspective view showing a main part of a conventional high-power Nd: YAG laser device.

[Explanation of symbols]

1 ... Nd: YAG rod, 1A ... Nd: YAG rod piece, 2 ... Lamp, 3 ... Reflector, 4 ... Plane output mirror, 5
... Convex total reflection mirror, 201 ... Nd: YAG slab, 201
A ... Nd: YAG slab piece, 301 ... Nd: YAG crystal, 301A ... Nd: YAG crystal piece, 401 ... Nd: Y
AG rod, 401A ... Nd: YAG rod piece, 404
… Clad layer.

Claims (3)

[Scope of utility model registration request] 1. A solid-state laser medium in which a plurality of solid-state laser medium pieces are arranged in the optical axis direction, and an optical contact surface, which is a bonding surface thereof, is fused and formed into a long length. 2. The solid-state laser medium according to claim 1, wherein the optical contact surface is heated to a temperature sufficient for fusing and is fused. 3. A solid-state laser device comprising a solid-state laser medium and a pumping light source for exciting the solid-state laser medium, wherein the solid-state laser medium is a long solid-state laser. A solid-state laser device using a medium.