WO2005055378A1

WO2005055378A1 - Fiber laser oscillating device

Info

Publication number: WO2005055378A1
Application number: PCT/JP2004/018080
Authority: WO
Inventors: Hiromichi Ota
Original assignee: Toyoda Koki Kabushiki Kaisha
Priority date: 2003-12-03
Filing date: 2004-11-29
Publication date: 2005-06-16
Also published as: JP3941063B2; JP2005167015A

Abstract

A fiber laser oscillating device able to receive more exciting lights and provide a larger-output laser beam. Exciting lights are input via a clad removed portion (10R) where at least a core member (12) remains and clad end faces formed by the clad removed portion at an arbitrary position in the longitudinal direction of an optical fiber (10). In addition, a plurality of exciting lights are input via the end faces of an optical fiber and at least one end face of clad end faces formed at an arbitrary position on a section vertical to the longitudinal direction of the optical fiber, with the optical fiber formed so that the core member deviates to a specified position from the center. Furthermore, clad removed portions and clad end faces are formed at proper intervals on one optical fiber to form an assembly end face formed by assembling a plurality of clad end faces, and an exciting light is input via that assembly end face.

Description

Description Fiber laser oscillator Technical field

The present invention relates to a fiber laser oscillating device that irradiates excitation light to an optical fiber having a core member containing a laser active substance therein and generates and amplifies laser light at a part of the core member. Background art

Conventionally, various fiber laser oscillators have been proposed that can obtain very high-quality laser light with high efficiency by using pump light having relatively poor beam quality.

As a conventional fiber laser oscillator, an end-pumped fiber laser oscillator comprising an optical fiber 10 and condenser lenses 24 and 26 is known as shown in FIG. 6 (A). The optical fiber 10 has, in the longitudinal direction, a core member 12 doped with a rare earth element such as neodymium (Nd), which is a laser active material, and the core member 12 is covered with a cladding member 14. In the example shown in FIG. 6 (A), the clad member 14 is further covered with the second clad member 16. Here, by setting the diameter of the core member 12 and the refractive indices of the core member 12, the cladding member 14 and the second cladding member 16 appropriately, relatively high efficiency and high quality laser light is generated. A possible fiber laser oscillation device can be realized relatively easily (in this case, the refractive index of the core member 12 is n 1, the refractive index of the clad member 14 is n 2, and the refractive index of the second clad member 16 is Is n3, the relationship is set to nl>n2> n3). Excitation from one end face Ta of this optical fiber 10 through the condenser lens 24 When the light emitting Lin (semiconductor laser or the like) is incident, the pumping light Lin excites the core member 12 while propagating through the cladding member 14 內 of the optical fiber 10 while repeating total reflection. In the excited core member 12, laser oscillation occurs, and only laser light Lout that can totally reflect the core member 12 残っ remains from the generated light and propagates in the core member 12. Therefore, by using the core member 12 having a small NA (numerical aperture) and a small diameter, a very high-quality laser light Lout can be obtained. It is expressed as the product of the half-angle of the angle. The smaller this product is, the higher the beam quality is.) Then, the laser light Lout emitted from the end face Tb is condensed by the condensing lens 26, and the condensed laser light Lout is used for various purposes.

However, in the end-pumped fiber laser oscillator shown in the example of FIG. 6 (A), it is difficult to increase the amount of incident pump light Lin (the area of the end face Ta of one optical fiber 10 is Therefore, it is very difficult to generate a laser beam Lout having a relatively large output.

Therefore, in the prior art disclosed in Japanese Patent Application Laid-Open No. 2001-158535, as shown in FIGS. 6 (B) and 6 (C), the core members 12 are arranged in a plane and further arranged. The prisms 4a and 4b are arranged on the upper surface, and the pumping light Lin is incident from a larger area via the prisms 4a and 4b (the pumping light is incident not from the end face of the optical fiber but from the side face). In this way, a laser light generator for increasing the output of the generated laser light has been proposed. In the prior art disclosed in Japanese Patent Application Laid-Open No. 2001-158535, the incident excitation light Lin is reflected at the boundary between the cladding member 14 and the glass plate 17 to generate the excitation light Lin. The incident angle of the excitation light Lin, the refractive index of the prism 4a, and the like are adjusted so as to be confined in the clad member 14.

Generally, in the optical fiber 10 used for the fiber laser oscillation device, the diameter of the clad member 14 is several 100 to 100 [μΐη]. Traditional When a semiconductor laser is used as the pump light L in of the end-pumped fiber laser oscillation device, it is difficult to focus the pump light having a relatively large output on the fiber end face Ta. Poor quality and relatively poor light collection).

In addition, in the conventional technique described in Japanese Patent Application Laid-Open No. 2000-158535, since the prisms 4a and 4b must be prepared, the fiber laser oscillation device becomes relatively expensive. . In addition, the pumping light L in is incident not from the end face of the optical fiber but from the side surface.When the pumping light is incident, the pumping light L in must be incident at a predetermined angle with respect to the optical fiber axis direction. The excitation light L in cannot be confined within the member 14, so that high accuracy is required for the incident angle, and the excitation light L in needs to be incident as parallel light. For this reason, it is very difficult to use a semiconductor laser having relatively poor light condensing properties for the excitation light L in.

The present invention has been made in view of such a point, and provides a fiber laser oscillation device capable of injecting more excitation light and obtaining a higher output laser light. That is the task. Disclosure of the invention

A first invention is a fiber laser oscillation device that has a core member containing a laser active substance in a longitudinal direction and emits pump light to an optical fiber in which the core member is covered with a clad member to generate laser light. Wherein at an arbitrary position in the longitudinal direction of the optical fiber, at least a clad-removed portion leaving the core member, and excitation light are incident from a clad end face formed by the clad-removed portion. There is a fiber laser oscillator.

According to the first invention, only the excitation light is incident from the end face of the optical fiber. Instead, the excitation light can be incident from the cladding end face provided at an arbitrary position in the longitudinal direction of the optical fiber. For this reason, more pump light can be incident, and a higher output laser beam can be obtained.

When removing the clad member so that only the core member is left, the area of the clad end face can be made larger and more excitation light can be incident from the clad end face.

In addition, when removing the clad member so as to leave the clad member of a predetermined thickness around the outer periphery of the core member, loss due to damage to the core member and adhesion of dust (diffuse reflection of propagating light, etc.) is suppressed. be able to.

A second invention is the fiber laser oscillation device according to the first invention, wherein a core member is shifted from a center to a predetermined position in a cross section perpendicular to the longitudinal direction of the optical fiber. .

According to the second aspect, since the core member is located at a position deviated from the center at the cladding end face and the fiber end face where the excitation light is incident, it is easy to enter the excitation light without being blocked by the core member. Thus, the efficiency can be further improved and a laser beam with a higher output can be obtained.

A third invention is a fiber laser oscillation device according to the first invention or the second invention, wherein a plurality of fiber laser end faces and at least one of the clad end faces formed at arbitrary positions are provided from a plurality of end faces. It is characterized in that excitation light is incident.

According to the third aspect of the present invention, a plurality of pump lights are incident from at least one of the optical fiber end face and the clad end face, so that a higher output laser beam can be obtained.

A fourth invention is the fiber laser oscillation device according to any one of the first to third inventions, wherein the cladding removing portion and the cladding end face are formed at an appropriate interval in one optical fiber. , Multiple clad end faces assembled It is characterized in that a collecting end face is formed and excitation light is incident from the collecting end face.

According to the fourth aspect, the optical fiber end face and the clad end face are collected at the location of the pump light, instead of the pump light being incident from the optical fiber end face and the clad end face. For this reason, even when it is difficult to converge the diameter of the excitation light to the diameter of one optical fiber or less, the excitation light can be efficiently incident, and a higher output laser beam can be obtained. Can be.

A fifth invention is the fiber laser oscillation device according to the fourth invention, wherein the end face of the clad and the Z or the end face of the optical fiber are formed in a polygonal shape.

According to the fifth aspect, the shape of the end face is polygonal (triangle, square, hexagon, etc.) so that the clad end face and the optical fiber end face are arranged as closely as possible on the collective end face. For this reason, the excitation light can be efficiently incident, and a higher output laser beam can be obtained. Brief Description of Drawings

FIG. 1 is a schematic configuration diagram (first embodiment) of one embodiment of a fiber laser oscillation device 1 of the present invention. FIG. 2 is a diagram illustrating the structure of an optical fiber 10 according to the second embodiment. FIG. 3 is a diagram illustrating an example in which a plurality of excitation lights Lin are incident from one end face in the second embodiment. FIG. 4 is a diagram for explaining a third embodiment. FIG. 5 is a diagram for explaining a fourth embodiment. FIG. 6 is a diagram illustrating a conventional fiber laser oscillation device. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration diagram of one embodiment of a fiber laser oscillation device 1 of the present invention.

[First Embodiment (Fig. 1)]

In the first embodiment, at an arbitrary position in the longitudinal direction of the optical fiber 10, a clad removing portion 10 R in which at least the core member 12 is removed and the clad member 14 is removed is formed to form the longitudinal direction. A feature is that a cladding end face S perpendicular to the direction is formed, and the excitation light Lin is also incident from the cladding end face S. Thus, more excitation light can be incident than in the conventional end-pumped fiber laser oscillation device, and a higher output laser beam can be generated.

The optical fiber 10 has a core member 12 containing a laser active substance (a rare earth element such as Nd) in the longitudinal direction, and the core member 12 is also a clad member 14 having a low refractive index. It is covered with.

In the example shown in FIG. 1 (A), the cladding member 14 is removed at any two places (cladding removing portion 10R) in one optical fiber 10 to form the clad end face S. . Note that the cladding removal portion 10R may be formed in any number of places.

FIG. 1 (B) shows the vicinity of the clad removing portion 10R. The clad end face S is perpendicular to the longitudinal direction of the optical fiber 10, and two opposing clad end faces S are formed by one clad removing portion 10R.

The optical fiber 10 used in this embodiment has a core member 12 doped with a rare-earth element Nd (neodymium) as a laser active material, and a semiconductor laser having a wavelength of 800 nm is used. When used for excitation light, it generates laser light with a wavelength of 1064 [nm]. The diameter φ core of the core member 12 is about 10 to 100.m], and the diameter φ clad of the cladding member 14 is about 100 to L 0 00 [m]. Also, the cladding removal part 10 The diameter ΦΓ of the core member 12 is formed to be about 0 to several 10 [μπι] larger than the diameter of the core member 12.

If the refractive index of the core member 12 is appropriately set so that “refractive index of the core member 12> refractive index of air”, the laser generated inside the core member 12 can be formed. Since the light can be totally reflected inside the core member 12 and confined, it is sufficient that at least the core member 12 is left. Of course, the clad member 14 having a predetermined thickness may be left.

FIG. 1 (C) shows a cross section perpendicular to the longitudinal direction of a general optical fiber 10 used for a fiber laser oscillation device. The outer periphery of the core member 12 (fluoride glass doped with a rare earth element, etc.) is covered with a cladding member 14 (glass fluoride, etc.) (refractive index of the core member 12> refractive index of the cladding member 14). The outer periphery of the lad member 14 is covered with a second clad member 16 (UV resin or the like) (refractive index of the clad member 14> refractive index of the second clad member 16), and the The outer periphery is covered with a covering member 19 (such as a covering resin). In the present embodiment, the optical fiber 10 is used. However, the present invention is not limited to the optical fiber 10 having this configuration.

Note that the purpose of the pump light L in is not to propagate it, but to confine it in the clad member 14 and apply it to the core member 12.Therefore, a covering member 19 that totally reflects the pump light L in is selected. May be.

In addition, the length of the optical fiber 10 from the end face T a (or T b) of the optical fiber 10 to the cladding end face S, and the length of the optical fiber 10 from the cladding removal part 10 R to the cladding removal part 1 OR The length is about 5 to 10 [m]. If this length is not appropriate, the incident excitation light Lin reaches the end face S (or the end faces Ta and Tb) before exciting the core member 12 and is emitted from the clad member 14. I will.

Next, referring to FIG. 1 (A), the components in the present embodiment and The functions of the components will be described.

The pumping light injector 2 OA is arranged at a position facing one end face Ta of the optical fiber 10, and the pumping light injector 20 B is arranged at a position facing the other end face Tb of the optical fiber 10. . In addition, the pumping light incidence device 20C is disposed at a position substantially facing each of the cladding end surfaces S.

The pumping light incidence device 20 C includes pumping light emitting means 20 (such as a semiconductor laser array), a collimating lens 22 that converts the emitted pumping light Lin into parallel light, and a pumping light converted into parallel light. It is composed of a condenser lens 24 that collects Lin. It should be noted that the lens group including the collimating lens 22 and the condensing lens 24 may have various other configurations. Then, the cladding removing section 10R is curved so that each of the excitation light incident devices 20C can be arranged at a position facing each of the cladding end faces S of the cladding removing section 10R. Then, the excitation light Lin emitted from the excitation light incident device 20C is incident on the cladding end surface S facing the excitation light incident device 20C.

The pumping light injector 2 OA is a mirror 30 a (a dichroic mirror) that transmits the pumping light Lin and reflects the laser light Lout generated inside the core member 12 with respect to the pumping light injector 20 C. Etc.) have been added. The mirror 30a is arranged in parallel with the end face Ta of the optical fiber 10.

The collimating lens 22 and the condensing lens 24 are similar to the excitation light incidence device 20C in that they convert the excitation light Lin emitted from the excitation light emission means 20 into parallel light and condense it. However, the laser beam L out generated in the core member 12 is emitted from the core member 12 on the end surface Ta of the optical fiber 10 to the excitation light incident device 20 A.

The laser light L out emitted from the core member 12 on the end face Ta of the optical fiber 10 is converted into parallel light by the condenser lens 24 (the condenser lens 24 serves as a collimating lens). The light is reflected by the mirror 30a. And The laser light L out reflected as parallel light is condensed by the condenser lens ² 4 (back to the core member 1 2 of the end face T a) which is incident on the core member 1 2 of the end face T a.

The excitation light incident device 20B is a mirror 30b (dichroic) that transmits the excitation light Lin and reflects the laser light Lout generated inside the core member 12 with respect to the excitation light incident device 20C. mirrors, etc.), and the output laser focusing lens ² 6 have been added. The mirror 30b is arranged so as to have an angle of about 45 ° with the end face T1> of the optical fiber 10.

The collimating lens 22 and the condensing lens 24 convert and condense the excitation light emitted from the excitation light emitting means 20 into parallel light, and are similar to the excitation light incidence device 20C. However, the laser light L out force S generated in the core member 12 and the excitation light incident device 20 B are emitted from the core member 12 on the end face Tb of the optical fiber 10.

The laser light L out emitted from the core member 12 of the end face T b of the optical fiber 10 is converted into parallel light by the condenser lens 24 (the condenser lens 24 functions as a collimating lens). The light is reflected by the mirror 30b in the direction of the output laser condenser lens 26 (taken out of the output laser condenser lens 26). The laser light L out reflected in a parallel light state is condensed by the output laser condensing lens 26 and can be used for various purposes.

In the present embodiment, an arbitrary number of cladding end faces S can be formed on a conventional end-pumped fiber laser oscillator to allow more pump light to enter. In the example shown in Fig. 1 (A), four pumping light injectors 20C are added to the conventional pumping light injectors 2OA and 20B, so that the pumping light is about three times as large. L in can be incident, and a higher output laser beam L out can be obtained.

[Second embodiment (Figs. 2 and 3)] The second embodiment differs from the first embodiment in the structure of the optical fiber 10.

As shown in FIG. 2, in a cross section perpendicular to the longitudinal direction of the optical fiber 10, the optical fiber 10 is positioned such that the position of the core member 12 is shifted from the center P of the cross section by a predetermined distance D. The difference is that they are formed. Thereby, the excitation light Lin can be more easily incident from the cladding end face S.

When the core member 12 is located at a position substantially at the center P of the clad end surface S, a part of the excitation light L in impinges on the core member 12 which is curved at the clad removing portion 10 R and is reflected or the like. As a result, there is a possibility that the cladding edge S may not be properly reached. However, according to the present embodiment, the vicinity of the center of the clad end surface S is a flat surface, and the core member 12 does not interfere, so that more excitation light Lin can be incident from the clad end surface S.

Further, as shown in FIG. 3, a plurality of pumping light injection devices 20C are arranged at positions corresponding to the cladding end surface S (or the end surface Ta or Tb of the optical fiber 10) and at an appropriate incident angle. And a plurality of excitation lights L in can be incident from one end face. In this case, the beam quality is slightly inferior (the error in the condensing diameter is slightly large, the converging diameter itself is slightly large, etc.). Is shifted from the center P of the end face T a or T b), so that more pumping light L in can be incident from the cladding end face S (or the end face T a or T b of the optical fiber 10).

[Third embodiment (Fig. 4)]

The third embodiment is different from the first embodiment in the method of bending the clad removing portion 10R.

As shown in FIG. 4 (A), the optical fiber 10 is folded by 180 ° at the cladding removing portion 10R, and the cladding end face S (and the end face of the optical fiber 10) is folded. 1

Form a bundle end face s s bunched together with the cottage & or 1>). By injecting a high-power excitation Lin having a diameter larger than that of the cladding end surface S from the gathering end surface SS which is sufficiently wider than the cladding end surface S, it is possible to obtain a laser beam L out having a higher output. .

Further, the shape of the cross section perpendicular to the longitudinal direction of the optical fibers 10 is preferably a polygonal shape that can be arranged as closely as possible. For example, by forming the cross section into a triangular shape, or by forming a square or hexagon as shown in FIGS. 4 (B) and 4 (C), the assembly end face SS can be formed without gaps.

4 (B) and 4 (C) show that the core member 12 is pulled out from both ends of the optical fiber 10 and the laser beam Lout output from one end face of the core member 12 is collected by the condenser lens 24. After being converted into parallel light (the condensing lens 24 functions as a collimating lens), the light is reflected by the mirror 30a, further condensed by the condensing lens 24, and returned to the core member 12. After converting the laser light Lout output from the other end face of the core member 12 into parallel light with the collimating lens 22, the laser light Lout is further condensed with the output laser condensing lens 26 and taken out. I have. In this case, from the collective end face SS, the pumping light incident device (excitation light incident device not including the mirrors 30a and 30b) having the same configuration as the pumping light incident device 20C is used. Lin is incident.

As a result, although the output of the excitation light Lin is large, it is possible to use an excitation light injection device in which it is difficult to make the condensing diameter smaller than the diameter of the cladding member 14 of the optical fiber 10 (^ clad or less). The output laser light Lout can be obtained.

Further, it is easy to arrange a plurality of excitation light incidence devices at positions corresponding to the collecting end face S S so that more excitation light is incident.

[Fourth embodiment (Fig. 5)] In the fourth embodiment, the excitation light incidence device 20C is arranged at a position facing the cladding end surface S of the plurality of cladding removing portions 1OR without using the mirrors 30a and 30b. This is an example of a fiber laser oscillation device having a simple configuration.

In the configuration of the fourth embodiment, the number of the cladding end face S and the number of the pumping light incidence devices 20C may be selected so that a target output laser light Lout can be obtained.

As described above, if the fiber laser oscillation device 1 of the present embodiment is used, the pump light L in can be incident from a plurality of locations of one optical fiber 10, so that the total pump light L in can be increased, and a higher output laser beam L out can be obtained.

The diameter of the clad member 1 4 to increase the excitation light L in <) when _C l _a d a is increased, the relative proportions of the cross-sectional area of the core member 1 2 to the cross-sectional area of the cladding member 1 4 is reduced However, the probability of excitation while hitting the core member 12 while being totally reflected within the cladding member 14 is reduced, and the oscillation efficiency is reduced. However, in the fiber laser oscillation device 1 shown in the present embodiment, it is not necessary to increase the diameter <i> clad of the cladding member 14, so that high oscillation efficiency can be maintained.

Further, in the conventional fiber laser oscillating device in which pumping light is incident from the side surface, a device (prism or the like) for inputting from the side surface of the optical fiber 10 and an adjustment for confining the incident pumping light Lin (for the pumping light). It is presumed that various cost increase factors and error factors, such as the angle of incidence on the prism) and the beam quality of the excitation light, are included. In the present embodiment, the excitation from the end face of the optical fiber 10 is performed. With a simpler configuration for entering the light Lin, the cost can be reduced and the error factor can be reduced.

The fiber laser oscillation device 1 of the present invention has the shape described in the present embodiment, The present invention is not limited to the configuration, the structure, and the like, and various changes, additions, and deletions can be made without changing the gist of the present invention.

The numerical values used in the description of the present embodiment are examples, and the present invention is not limited to these numerical values.

In the present embodiment, a semiconductor laser is used for the excitation light Lin, but the present invention is not limited to this. Industrial applicability

The fiber laser oscillation device of the present invention can be applied to various devices using laser light, such as a laser processing device.

Claims

The scope of the claims

1. A fiber laser oscillating device that has a core member containing a laser active substance in a longitudinal direction and emits a laser beam by injecting excitation light into an optical fiber in which the core member is covered with a cladding member,

A fiber, characterized in that at an arbitrary position in the longitudinal direction of the optical fiber, at least a clad-removed portion leaving a gore member, and excitation light is incident from a clad end face formed by the clad-removed portion. Laser oscillation device.

2. The fiber laser oscillation device according to claim 1, wherein

A fiber laser oscillation device, wherein a core member is shifted from a center to a predetermined position in a cross section perpendicular to the longitudinal direction of the optical fiber.

3. The fiber laser oscillator according to claim 1, wherein

A fiber laser oscillation device, wherein a plurality of excitation lights are incident from at least one end face of an optical-fiber end face and the clad end face formed at an arbitrary position.

4. The fiber laser oscillator according to claim 1, wherein

Forming the clad removing portion and the clad end face at appropriate intervals in one optical fiber to form a collective end face in which a plurality of clad end faces are collected, and exciting light is incident from the collective end face. Characteristic fiber laser oscillator.

5. The fiber laser oscillation device according to claim 4, wherein

A fiber laser oscillation device, wherein the end face of the clad and the Z or the end face of the optical fiber are formed in a polygonal shape. Figure

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