JPH11284255A - Fiber laser device and laser machining device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser device which significantly improve laser output while advantages of fiber laser such as excellence in light condensing characteristics and thermal stableness in output and lateral mode are maintained. SOLUTION: A laser fiber 1 is wound around an outer peripheral surface 2a of a glass cylinder 2 which is a structure body for confining excitation light L1 and L2 for exciting the laser fiber 1, the excitation light L1 L2 from laser diodes 41 and 42 are made incident near the outer peripheral end part of an end surface 2b of the glass cylinder 2 through prisms 31 and 32 for confinement through repeated total reflections on the inner side surface of the outer peripheral surface 2a, and the confined excitation light is guided into the laser fiber 1 through a part contacting to the glass cylinder 2 for excitation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser device that oscillates a laser by supplying excitation light to a laser active substance inside an optical fiber.

[0002]

2. Description of the Related Art In the field of optical communication or laser processing, it has been desired to develop a laser device having a higher output and a lower cost. However, an optical fiber laser device has been known as a device which is more likely to satisfy this demand. Have been. In an optical fiber laser device, the transverse mode of laser oscillation can be made relatively simple by appropriately selecting the core diameter, the refractive index difference between the core and the clad, and the like. Also,
By confining the light at a high density, the interaction between the laser active substance and the light can be enhanced. In addition, since the interaction length can be increased by increasing the length of the optical fiber, a spatially high-quality laser beam can be generated with high efficiency. Therefore, high quality laser light can be obtained at relatively low cost.

Here, in order to further increase the output or efficiency of the laser light, an area (usually a core) to which laser active ions or dyes of an optical fiber and other luminescent centers (hereinafter referred to as laser active substances) are added. Section), it is necessary to efficiently introduce the excitation light. However, usually, when the core diameter is set so as to satisfy the single-mode waveguide condition,
Since the diameter is limited to ten and several μm or less, it is generally difficult to efficiently introduce the excitation light to this diameter. As a means for overcoming this, a so-called double-clad fiber laser has been proposed (see, for example, H.E.
Zenmer, U.S.A. Willowski, A .; Tu
Nnermann, and H .; Welling, Op
tics Letters. Vo1.20, No. 6,
pp, 578-580, March, 1995. reference).

In a double clad fiber laser,
There is a first clad portion having a lower refractive index than the core portion around the core portion, and a second clad portion having a lower refractive index is provided outside the first clad portion. As a result, the excitation light introduced into the first cladding propagates while being confined in the first cladding due to total reflection due to a difference in refractive index between the first cladding and the second cladding. I do. During this propagation, the excitation light repeatedly passes through the core, and excites the laser active substance in the core. Since the first cladding has an area about several hundred to 1,000 times larger than the core, more pumping light can be introduced and higher output can be achieved.

[0005]

The double clad type fiber laser has the advantages of high oscillation efficiency, a single oscillation transverse mode and stability, and uses a laser diode (hereinafter, LD). Since an output of about several watts to about 10 watts can be obtained, it can be said that the output was much higher than that of a core-pumped fiber laser before that.

However, since the above-mentioned double clad type fiber laser is ultimately pumped from one or both ends of the fiber, there is a problem that the number of pumping LDs cannot be increased. In other words, high brightness of LD
It can be said that there is no method for increasing the output other than increasing the output. As a means intuitively conceived as a method for overcoming this drawback, there is a method of increasing the output by bundling a plurality of double-clad fiber lasers. In this case, the average output can be increased by the number of bundles, but the cladding part (about 100 times in diameter), which is much larger than the core, is attached to each core part. There is a problem that the brightness is reduced due to the fact that the portion is widely scattered in the space.

SUMMARY OF THE INVENTION The present invention has been made under the above-mentioned background, and maintains the advantages of a fiber laser such as excellent light-collecting properties and stable thermal output and transverse mode while maintaining the laser output. It is an object of the present invention to provide a laser device capable of significantly improving the laser beam.

[0008]

Means for Solving the Problems As means for solving the above-mentioned problems, the invention of claim 1 has a core containing a laser active substance, and when the active substance is excited, a laser beam is emitted from an end. An output optical fiber, an excitation light source for generating excitation light for exciting the active substance, and a structure capable of confining the excitation light, wherein at least a part of the side surface of the optical fiber and the structure are directly or optically. A fiber laser device which is indirectly contacted via a medium, and the active substance is excited by excitation light incident through the contacted portion.

According to a second aspect of the present invention, the structure has a shape around which an optical fiber can be wound, and the excitation light is totally reflected on the surface of the structure and / or the surface of the optical medium in contact with the structure. 2. The fiber laser device according to claim 1, wherein the excitation light is extracted from the structure to the optical fiber from a portion in contact with the side surface of the optical fiber. 3.

According to a third aspect of the present invention, an optical fiber is wound around the side surface of the columnar structure, and the excitation light incident on the structure is entirely exposed to the side surface of the structure and / or the surface of the optical medium in contact with the side surface. 3. The fiber laser device according to claim 2, wherein the fiber laser device has a structure in which reflection is repeated and an active substance contained in the core is absorbed while drawing a helical optical path around an axis of the structure.

According to a fourth aspect of the present invention, the excitation light is incident from a bottom surface of the columnar structure.
2. The fiber laser device according to item 1.

According to a fifth aspect of the present invention, at least a part of the columnar structure has a shape in which an area of a cross section perpendicular to an axis of the structure continuously changes along the axial direction. The fiber laser device according to claim 3 or 4, wherein:

According to a sixth aspect of the present invention, there is provided a prism adhered to the surface of the structure, a prism adhered to the surface of the structure via an optical medium, a groove provided directly on the surface of the structure, A groove provided in the optical medium closely attached to the body surface, a diffraction grating provided on the surface of the structure, or a portion selected from a diffraction grating provided on the optical medium closely attached to the surface of the structure. The fiber laser device according to any one of claims 1 to 5, wherein excitation light is incident on the structure.

According to a seventh aspect of the present invention, an optical fiber is wound around the structure, and at least a part of the wound optical fiber has a refractive index equal to or greater than that of the structure. 7. The fiber laser device according to claim 1, wherein the fiber laser device is covered with an optical medium.

The invention according to claim 8 is such that an optical fiber is wound around the structure, and at least a part of the wound optical fiber is covered with an optical medium having a smaller refractive index than the outermost periphery of the optical fiber. The fiber laser device according to any one of claims 1 to 7, wherein:

According to a ninth aspect of the present invention, there is provided a laser processing apparatus having a fiber laser device and a condensing optical system for condensing a laser beam emitted from the fiber laser device on an object to be processed. A laser processing apparatus using the fiber laser apparatus according to any one of claims 1 to 8.

[0017]

(Embodiment 1) FIG. 1 is a perspective view showing a schematic configuration of a fiber laser apparatus according to Embodiment 1 of the present invention. As shown in FIG. 1, in the fiber laser device of this embodiment, a laser fiber 1 is wound around a circumferential surface 2a of a glass cylinder 2, and one end face in the axial direction of the glass cylinder 2 (upper end face in the figure) ) at the end of the outer periphery of the 2b is attached is a prism 31 for introducing the two excitation light and excitation light L ₁ and L is introduced into the glass cylinder 2 through the prisms 31 and 32 ₂ , two semiconductor laser devices 41 and 42 for generating the laser beams 2 respectively. The pumping lights L ₁ and L ₂ are guided to the vicinity of the entrance surfaces of the prisms 31 and 32 through optical fibers 41 a and 42 a coupled to the semiconductor laser devices 41 and 42, respectively, and are made substantially parallel light through the collimator lenses 41 b and 42 b. After that, the light enters the prisms 31 and 32.

The laser fiber 1 has a core diameter of 90 μm.
m, a laser fiber having a cladding diameter of 100 μm and a length of 50 m. The core of the laser fiber 1 is doped with Nd ³⁺ ions at a concentration of 0.5 at%. As the base material of the fiber, a phosphate glass (for example, LHG-8 manufactured by HOYA Corporation) can be used. After planar polishing, one end of the fiber has a reflectance of 98 at a laser oscillation wavelength of 1.06 μm.
%, And the other end is coated with a multilayer film having a reflectance of about 10% at a laser oscillation wavelength of 1.06 μm.

The glass column 2 has a diameter of 10 cm and a length of 5 cm.
cm Pyrex glass cylinder. Optical polishing is applied to both end surfaces and the outer peripheral surface.

The semiconductor laser devices 41 and 42 are fiber-coupled semiconductor laser devices having an oscillation wavelength of 0.8 μm and an output of 15 W, and output oscillation laser light to the outside through optical fibers 41a and 42a.

As the collimating lenses 41b and 42b, aspherical lenses having a focal length of about 7 mm (for example, LM-A129 manufactured by HOYA Optics Co., Ltd.) can be used.

FIG. 2 is an enlarged side view near the prism 31 in FIG. 1, and FIG. 3 is an enlarged plan view near the prism 31 in FIG. The configuration near the prism 32 is the same as the configuration near the prism 31. As shown in FIGS. 2 and 3, the prism 31 is a so-called triangular prism type prism, and one of the three surfaces excluding the two side surfaces that are parallel to each other is an incident surface 31 a, and the other one is an incident surface 31 a.
The surface (bottom surface) is closely fixed to the end surface 2 b of the glass cylinder 2.

Excitation light L emitted from optical fiber 41a
₁ is incident from the incident surface 31a of the prism 31 is substantially collimated by the collimator lens 41b, is introduced from a point I ₀ of the end face 2b of the glass cylindrical member 2 into the glass cylinder 2. The angle θ between the excitation light L1 incident on the glass cylinder ₁ and the end face 2b of the glass cylinder 2 was set to be about 5 °. As shown in FIG. 3, the direction of the excitation light L <b> _{1 in} a plan view is a direction parallel to the tangent S at the point I of the contour circle of the end surface 2 b of the glass cylinder 2. Incidentally, the point I is the point at which a line connecting the center and the point I ₀ of the glass cylindrical member 2 intersects with the contour circle. Eggplant distance d between the excitation light L ₁ and the tangent line S is set to about 1 mm.

The excitation light _{L 1} incident on the glass cylindrical member 2,
It reaches the inner surface of the circumferential surface 2a, where it is totally reflected by the difference in the refractive index between glass and air. Excitation light L totally reflected
₁ also goes straight on and progresses downward through the glass cylinder 2 while drawing a spiral locus near the inner surface of the circumferential surface 2a by repeating total internal reflection on the inner surface of the circumferential surface 2a one after another. Then, the light is totally reflected to the end face (bottom face) opposite to the end face 2b, and travels toward the end face 2b. As a result, the total reflection is repeated inside the glass cylinder 2 and confined in the glass cylinder 2. It becomes a state like that. This point is the excitation light L
_The same is true for No. ₂ .

[0025] Figure 4 is determined by a computer simulation of the trajectory of the excitation light _{L 1} three-dimensional (x, y,
FIG. 5 is a view of the locus of FIG. 4 viewed from the z-axis direction (the axial direction of the glass cylinder 2), and FIG. 6 is a view of the locus of FIG. 4 viewed from the side direction (y-axis direction). FIG. 7 is a view of the trajectory of FIG. 4 viewed from the side (x-axis direction).

Here, the laser fiber 1 is wound around the outer peripheral surface 2a of the glass cylinder 2. That is, the cladding portion of the laser fiber 1 is in close contact with the outer peripheral surface 2a, that is, the optical fiber is partially optically coupled. The refractive index of the glass cylinder 2 and the refractive index of the cladding of the laser fiber 1 are substantially equal. Therefore, the excitation light is introduced if without being totally reflected excitation light L ₁ reaches the contact portion to the laser fiber 1. Therefore, the excitation light L ₁ trapped in the glass cylindrical member 2,
While circulating in the glass cylinder 2, it is introduced into the laser fiber 1 with high efficiency.

[0027] In this embodiment, the output end of the laser fiber 1, it was possible to obtain a good output laser beam L ₀ of the laser output 8W at a wavelength of 1.06 .mu.m.

Therefore, a condensing lens system (focal length 10 m) for condensing the output laser light of this fiber laser device.
m), the laser processing apparatus was configured, and energy of 90% or more of the output could be collected within a diameter of 200 μm. In that case, the focused diameter of the output laser light was always stable irrespective of the laser output and the state of heat.

In the fiber laser device of the above embodiment, the laser fiber 1 is wound around the outer peripheral surface of the glass cylinder 2 many times, and the inner peripheral surface of the outer peripheral surface repeats total internal reflection while mainly repeating the inner surface of the glass cylinder 2. Since the pumping light is introduced into the laser fiber 1 by introducing the pumping light into the glass cylindrical body 2 so as to be in a state of being confined in the glass cylinder 2, extremely highly efficient pumping is possible.

Further, since the light travels in the vicinity of the inner surface of the circumferential surface 2a of the glass cylindrical body 2 while drawing a spiral trajectory, the confined light beam may interfere with the light source or the light entrance. Therefore, it is possible to use a large number of light sources, and further increase the output of the laser.

Although the output value of the above embodiment is not the limit of this fiber laser device, only 8 W is output because the number of semiconductor laser arrays prepared for excitation is small, but the upper limit of the laser device is 1 kW or more. It is expected to be.

In the above embodiment, the incident light L ₁ , L ₂
Although the example in which the angle θ with respect to the end surface 2b is set to 5 ° has been described, this may be another angle. For example, setting θ to a small value decreases the spiral pitch, and increasing θ increases the spiral pitch. 8, 9, and 10 are diagrams showing the trajectories of the excitation light in the glass cylinder 2 when θ is set to 1 °. FIGS. 11, 12, and 13 show the glass cylinder when θ is set to 10 °. FIG. 3 is a diagram illustrating a locus of excitation light in a body. θ can be selected to an appropriate value according to the characteristics of the laser fiber 1, the size of the glass cylinder 2, the target output, and the like.

Furthermore, in the above embodiment, the excitation light is introduced into the glass cylinder 2 through the prisms 31 and 32, so that the loss due to surface reflection during the introduction is reduced. As shown in FIG. 14, the diffraction grating 5 may be used instead of the prisms 31 and 32, or the groove 6 may be formed.

In the above-described embodiment, an example in which the laser fiber 1 is wound in a single layer around the glass cylinder 2 has been described.
It may be wound in multiple layers.

Further, in the above-described embodiment, an example using a glass cylinder is given, but this is not necessarily glass, and any material that is transparent to excitation light may be used.
For example, plastic or the like can be used.

(Embodiment 2) FIG. 15 is a partial sectional view showing an outline of a fiber laser device according to Embodiment 2 of the present invention. As shown in FIG. 15, in this embodiment, a spiral groove (screw shape) having a pitch of 0.2 mm is formed on the outer peripheral surface 2a of the glass cylinder 2 to form a spiral groove 2c.
The laser fiber 1 is wound so as to be fitted into the spiral groove 2c.
The transparent adhesive layer 7 is formed on the outer peripheral surface 2a so as to cover. The other configuration is the same as that of the first embodiment, and the detailed description is omitted.

In this embodiment, a better result of 9 W of laser output at a wavelength of 1.06 μm was obtained. In addition,
A glass or other resin layer may be provided instead of the transparent adhesive layer 7. It is preferable that the refractive index of the transparent adhesive layer, glass, or another resin layer, which is the optical medium, is equal to or close to the refractive index of the glass cylinder, which is the structure. Further, the optical medium can be used for a structure having no spiral groove. In addition to such a role as an optical medium, it also plays a role in firmly fixing the fiber. Also, in this embodiment, a modification similar to that of the first embodiment can be considered.

(Embodiment 3) FIG. 16 is a perspective view showing a schematic configuration of a fiber laser apparatus according to Embodiment 3 of the present invention. As the glass cylinder 2 in Example 1, the diameter at the upper end in the figure is 10 cm, the diameter at the lower end is 9.8 cm,
A tapered glass cylinder having a length of 10 cm is used, and a laser fiber 1 is wound below the glass cylinder 2 in the figure, and the transparent adhesive is further covered so as to cover the wound laser fiber 1. The layer 7 is formed on the outer peripheral surface 2a. The other configuration is the same as that of the first embodiment, and the detailed description is omitted.

In this embodiment, the glass cylinder 2 is a tapered glass cylinder having a tapered shape.
A trajectory is drawn such that the spiral pitch becomes denser as the laser fiber 1 is wound down.

FIG. 17 shows excitation light L obtained by computer simulation when θ was set to 10 ° in the fiber laser device according to the third embodiment.
₁ locus three-dimensional (x, y, z) to the indicated figures, FIG. 1
8 is a view of the trajectory shown in FIG. 17 viewed from the z-axis (the axial direction of the glass cylinder 2), FIG. 19 is a view of the trajectory shown in FIG. 17 viewed from the side (y-axis direction), and FIG. 3 is a view of the trajectory shown in FIG.

When the glass cylinder 2 is formed of a tapered cylinder, the trajectory of the excitation light changes in the spiral pitch by changing θ.
Draw a locus as shown in FIG.

In this embodiment, θ was set to 10 °. As a result, a locus that once stagnated at about 8 cm below the incident surface (end surface 2b) and then returned toward the incident surface was drawn. Therefore, in this example, the effect that the pumping efficiency becomes higher in the vicinity where the pumping light once stagnates was obtained, and a very good result of a laser output of 11 W at a wavelength of 1.06 μm was obtained.

Therefore, a condensing lens system (focal length 10 m) for condensing the output laser light of this fiber laser device.
m), the laser processing apparatus was configured, and energy of 90% or more of the output could be collected within a diameter of 200 μm. In that case, the focused diameter of the output laser light was always stable irrespective of the laser output and the state of heat.

In the above embodiment, the example of the tapered shape of the glass cylindrical body 2 is a simple tapered shape in which the diameter is linearly reduced. It may be a tapered shape, or a shape in which the diameter is constant up to the middle and becomes tapered from the middle.

(Embodiment 4) FIG. 21 is a view showing a schematic configuration of a fiber laser apparatus according to Embodiment 4 of the present invention. This embodiment is the same as Embodiment 3 except that the excitation light enters the glass cylinder 2 not through the end face 2b but through the incident groove 300 provided on the outer peripheral face 2a. In the following, only the differences will be described, and description of the same portions will be omitted.

The entrance groove 300 has a length of about 10 mm, a width of about 1 mm, and a depth of about 0.7 mm formed on the outer peripheral surface 2a of the glass cylinder 2 where the laser fiber 1 is not wound.
V-shaped groove. The semiconductor laser array 400 having a cylindrical lens 400b having an oscillation wavelength of 0.8 μm and an output of 20 W was used as a generator of the excitation light incident from the incident groove 300. Although not shown, in this embodiment, two incident grooves 300 are provided, and the excitation light is introduced into the glass cylinder 2 using two semiconductor laser arrays 400.

As a result, a relatively good result of a laser output of 6 W at a wavelength of 1.06 μm was obtained. Therefore, when a laser processing apparatus was configured by providing a condensing lens system (focal length 10 mm) for condensing the output laser light of this fiber laser apparatus, energy of 90% or more of the output could be collected within a diameter of 200 μm. . In that case, the focused diameter of the output laser light was always stable irrespective of the laser output and the state of heat.

(Embodiment 5) FIG. 22 is a view schematically showing a fiber laser apparatus according to Embodiment 5 of the present invention.
FIG. 23 is a partial sectional view of the fiber laser device of FIG. As shown in these figures, the fiber laser device of this embodiment is the same as the fiber laser device of FIG.
a, a resin fiber 70 is wound on the outer peripheral surface 2 so as to cover the laser fiber 10.
0a and fixed. Also, three excitation light introducing prisms 331, 332, 333 are provided on one end surface of the glass tube 20, that is, on the upper end surface 20b in the drawing, in optical close contact. The main difference between this embodiment and the above-described embodiments is that a glass tube 20 is used in place of the glass column 2.

The glass tube 20 has an outer diameter of 10 cm and a length of 1 cm.
This is a quartz glass tube having a thickness of 0 cm and a thickness t of 1.5 mm. The upper and lower end surfaces of the glass tube 20 are formed in parallel with a plane perpendicular to the center axis of the tube and are mirror-polished. The outer peripheral surface is also mirror-polished.

The laser fiber 10 wound on the outer peripheral surface 20a of the glass tube 20 has a core 10a having a diameter of 90 μm, a clad 10b having a diameter of 125 μm, and a length of 1 μm.
It is a 50 m laser fiber. The core portion 10a of this laser fiber is doped with Nd ³⁺ ions at a concentration of 0.2 at%. The base material of the fiber is quartz glass. One end surface in the longitudinal direction of the laser fiber is coated with a multilayer film after the surface is planarly polished. The reflectance of this one end face is 98% or more with respect to the laser oscillation wavelength of 1.06 μm. Further, the other end face of the laser fiber is a face obtained by simply breaking the fiber vertically, and is not subjected to a coating treatment or the like. The reflectance of the other end surface is about 4% with respect to the laser oscillation wavelength of 1.06 μm.

As the resin layer 70, an ultraviolet curable resin having a refractive index close to 1.47 of quartz glass (for example,
OGl2 from EPOXYTECHNOLOGY, USA
Although 5) was used, glass having a refractive index close to that of a glass tube may be used.

Although not shown, an excitation light source for exciting the fiber laser apparatus has an oscillation wavelength of 0.8.
Three fiber-coupled semiconductor laser devices having a power of 15 μm and a power of 15 W are used. A lens is attached to the light emitting portion of each fiber-coupled semiconductor laser device, and the exciting light for excitation is condensed into a beam having a diameter of 600 μm, and the three prisms 331 and 33 for entering the exciting light are respectively described above.
2,333 into the glass tube 20.

In this case, the incident angle at which each excitation light is incident on the upper end surface 20b of the glass tube 20 is about 5 °. In addition, the direction when each excitation light is projected and viewed from the center axis direction of the circular tube is at a point where a straight line connecting the center of the circular tube and the incident point of the excitation light intersects the outer peripheral surface 20a on a plane including the upper end surface. The direction is substantially parallel to the tangent to the outer peripheral surface.

As a result, a very good result of a laser output of 17 W at a wavelength of 1.06 μm was obtained. In addition, this output value is not the limit of this fiber laser device,
Although 17 W is not output because the number of semiconductor laser devices prepared for excitation is small, higher output can be obtained by using a larger number of semiconductor laser devices. The upper limit of the output of the fiber laser device of this embodiment is at least 1 k
It is expected that there will be more than W.

When the output of this fiber laser device was condensed by a lens system having a focal length of 10 mm, a diameter of 200 mm was obtained.
Energy of 90% or more of the output could be collected within μm. The focused diameter of this fiber laser device was always stable irrespective of the laser output and the state of heat.

In this embodiment, heat radiation is improved by using a glass tube as a structure for confining the excitation light.
This is advantageous for high average output operation. The thinner the thickness of the glass tube, the better the heat radiation. Also, the thinner the glass tube, the higher the pumping efficiency of the laser fiber.
As described above, it is desirable that the shape of the structure for confining the excitation light is a hollow shape having an opening. By using a structure having such a shape, heat dissipation is improved, and a high average output operation is performed. It is advantageous. In this case, the hollow shape may be any shape in principle.

In addition, the use of quartz glass instead of phosphate-based laser glass as the base material of the laser fiber 10 improves the laser light resistance, which is advantageous for high-luminance operation. Of course, in Examples 1 to 4, the quartz glass laser fiber as in this example can be used.

In this embodiment, the entrance of the excitation light
Although a method in which a prism is adhered to the end surface of the glass tube is used, a V-groove processing may be performed on the end surface of the glass tube, or a diffraction grating may be formed. In short, any entrance may be used as long as the excitation light can be incident.

Further, the refractive index of the optical medium (in the fifth embodiment, the same as that of the resin layer but of glass) in contact with the structure capable of confining the excitation light is the same as that of the structure (the quartz glass tube in the fifth embodiment). However, the same is true for structures of other materials or shapes), but the refractive index may be higher than that of the above structures. However, if the refractive index is lower than that of the structure, the excitation light that has entered the structure is almost totally reflected at the interface with the optical medium and cannot enter the laser fiber, so that the laser fiber is hardly excited. Become. Further, it is preferable that the refractive index of the optical medium be equal to or less than the refractive index of the core of the optical fiber in order to efficiently guide the excitation light to the core.

Although a fiber-coupled semiconductor laser device is used as a pumping light source, an LD chip or an LD array provided with a collimating lens may be used.

In the above embodiment, an example in which a glass cylinder and a cylindrical body are used as the structures capable of confining the excitation light has been described, but other structures having the same function may be used. Although a semiconductor laser device is used as a source of excitation light, another laser device or a light generating device other than a laser device may be used.

[0062]

As described above in detail, according to the present invention, a part of the side surface of the laser fiber is brought into direct or indirect contact with a structure capable of confining the excitation light for exciting the laser fiber, and the contact is made. Excitation light is introduced into the laser fiber through the part to excite it, which allows the excitation light from multiple excitation light sources to be confined in the above structure and absorbed by the laser fiber, making it difficult It has made it possible to increase the output of fiber laser devices.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a schematic configuration of a fiber laser device according to a first embodiment of the present invention.

FIG. 2 is an enlarged side view of the vicinity of a prism 31 in FIG.

FIG. 3 is an enlarged plan view near a prism 31 in FIG.

4 is a view three-dimensionally (x, y, z) to be determined by a computer simulation of the trajectory of the excitation light L ₁ in a fiber laser device according to the first embodiment.

5 is a diagram of the locus of FIG. 4 as viewed from the z-axis direction (the axial direction of the glass cylinder 2).

FIG. 6 is a view of the trajectory of FIG. 4 as viewed from a side surface direction (y-axis direction).

FIG. 7 is a diagram of the trajectory of FIG. 4 viewed from a side surface (x-axis direction).

8 is a view three-dimensionally (x, y, z) to be determined by the trajectory computer simulations of the excitation light L ₁ in a case where the θ in a fiber laser device according to Example 1 in 1 °.

9 is a diagram of the locus of FIG. 8 as viewed from the z-axis direction (the axial direction of the glass cylinder 2).

FIG. 10 is a diagram of the trajectory of FIG. 8 as viewed from a side surface direction (y-axis direction).

11 is a view three-dimensionally (x, y, z) to be determined by the trajectory computer simulations of the excitation light L ₁ in a case where the θ in a fiber laser device according to Example 1 to 10 °.

12 is a diagram of the locus of FIG. 11 viewed from the z-axis direction (the axial direction of the glass cylinder 2).

FIG. 13 is a diagram of the trajectory of FIG. 11 viewed from a side surface direction (y-axis direction).

FIG. 14 is a diagram showing a modification of the first embodiment.

FIG. 15 is a partial cross-sectional view schematically illustrating a fiber laser device according to a second embodiment of the present invention.

FIG. 16 is a partial cross-sectional view schematically illustrating a fiber laser device according to a third embodiment of the present invention.

17 is a view three-dimensionally (x, y, z) to be determined by the trajectory computer simulations of the excitation light L ₁ in a case where the θ in a fiber laser device according to Example 3 to 10 °.

18 is a diagram of the locus of FIG. 17 as viewed from the z-axis direction (the axial direction of the glass cylinder 2).

FIG. 19 is a diagram of the trajectory of FIG. 17 as viewed from a side surface direction (y-axis direction).

20 is a diagram of the trajectory of FIG. 17 as viewed from a side surface direction (x-axis direction).

FIG. 21 is a partial cross-sectional view schematically showing a fiber laser device according to a fourth embodiment of the present invention.

FIG. 22 is a diagram schematically illustrating a fiber laser device according to a fifth embodiment of the present invention.

FIG. 23 is a partial cross-sectional view of the fiber laser device of FIG.

[Explanation of symbols]

1: laser fiber, 2: glass cylinder, 31, 3
2 ... Prism, 41, 41 ... Laser diode, 41
b, 42b: Collimating lens.

Claims (9)

[Claims] 1. An optical fiber having a core containing a laser active substance and outputting a laser beam from an end when the active substance is excited, and an excitation light source generating excitation light for exciting the active substance And a structure capable of confining the excitation light, wherein at least a part of the side surface of the optical fiber and the structure are in direct contact with each other or indirectly via an optical medium,
A fiber laser device, wherein the active substance is excited by excitation light incident through the contacted portion. 2. The structure has a shape around which an optical fiber can be wound, and the surface of the structure and / or
Alternatively, the excitation light repeats total reflection on the surface of the optical medium in contact with the structure, and the excitation light is extracted from the structure to the optical fiber from a portion in contact with the side surface of the optical fiber. Item 7. A fiber laser device according to item 1. 3. An optical fiber is wound around the side surface of the columnar structure, and the excitation light incident on the structure repeatedly undergoes total reflection on the side surface of the structure and / or the surface of the optical medium in contact with the side surface. 3. The fiber laser device according to claim 2, wherein the fiber laser device has a structure in which the active material contained in the core is absorbed while drawing a helical optical path around the axis of the structure. 4. The fiber laser device according to claim 3, wherein the excitation light enters from a bottom surface of the columnar structure. 5. The structure according to claim 1, wherein at least a part of the columnar structure has a shape in which an area of a cross section perpendicular to an axis of the structure changes continuously along the axial direction. The fiber laser device according to 3 or 4. 6. A prism adhered to the surface of the structure, a prism adhered to the surface of the structure via an optical medium, a groove provided directly on the surface of the structure, and a prism adhered to the surface of the structure. The groove provided in the optical medium, the diffraction grating provided on the surface of the structure, or the portion selected from the diffraction grating provided on the optical medium closely attached to the surface of the structure, in the structure. The fiber laser device according to any one of claims 1 to 5, wherein the excitation light is incident. 7. An optical fiber is wound around the structure, and at least a part of the wound optical fiber is covered with an optical medium having a refractive index equal to or higher than that of the structure. The fiber laser device according to any one of claims 1 to 6, wherein: 8. An optical fiber is wound around the structure, and at least a part of the wound optical fiber is covered with an optical medium having a smaller refractive index than the outermost periphery of the optical fiber. The fiber laser device according to any one of claims 1 to 7, wherein: 9. A laser processing apparatus comprising: a fiber laser device; and a condensing optical system for condensing a laser beam emitted from the fiber laser device on a processing target, wherein the fiber laser device is used as the fiber laser device. 8
A laser processing apparatus using the fiber laser apparatus described in any one of the above.