JP2011186267A - Optical fiber condenser and laser device employing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber condenser that suppresses leakage of laser beam in a reduced diameter area of the tip, reduces an outer diameter of the tip of a fiber bundle, and also reduces a core diameter of fiber for output. <P>SOLUTION: In the optical fiber condenser, between fiber for input 11 comprising a bundle of a plurality of optical fibers 111 and fiber for output 12 comprising an optical fiber having one core 122, tapered part fiber 13 comprising a bundle of a plurality of other optical fibers 131 is provided. The diameter of each core 132 of the plurality of other optical fibers 131 constituting the tapered part fiber 13 is made up to be bigger than the diameter of each core 112 of the plurality of optical fibers 111 constituting the fiber for input 11, thereby suppressing the generation of leaked light in the distal end area of the tapered part fiber 13. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical fiber type concentrator capable of condensing single mode light emitted from a plurality of laser light sources onto one output fiber, and a laser apparatus using the same.

  As a method of increasing the output of the laser device, in addition to the method of increasing the output of the laser device itself, unit laser units are installed in parallel, and the laser light output from each laser unit is condensed and added to increase the output. A method is also used.

  In the latter case, if light is to be collected by a spatial coupling system using a lens or the like, it is necessary to make a fine adjustment to align the optical axis. In addition, since a fine movement device must be added, the optical system becomes complicated. In addition, it is not known when the optical axis shift occurs, and once the optical axis is deviated, it takes time for fine adjustment again. In the worst case, the optical axis may be shifted during laser oscillation and the space coupling system itself may be destroyed.

  On the other hand, in an optical fiber type concentrator using an optical fiber as a concentrator, it can be handled by fusion-bonding the output fiber of the unit laser unit and the input optical fiber of the optical fiber type concentrator. There is an advantage that there is no need for adjustment. In addition, the device structure can be simplified.

  An optical fiber type concentrator is formed by bundling a plurality of input optical fibers and integrating one end thereof to provide a tapered diameter-reduced region having a tapered shape, to which an output optical fiber is coupled. . Light incident on the plurality of input optical fibers is condensed and added in the reduced diameter region, and is combined into one output optical fiber. In order to improve the light density of the light emitted from the optical fiber concentrator, it is required to reduce both the cross-sectional area of the tip portion of the tapered structure and the core cross-sectional area of the output optical fiber.

  For example, Patent Documents 1 to 3 disclose devices that propagate light using an optical fiber having a tapered shape.

  Patent Document 1 describes a technique regarding an optical fiber type collector that collects and adds multimode light. That is, a plurality of input-side optical fibers are bundled and coupled to the output-side optical fiber via a tapered diameter-reduced region.

  Patent Document 2 describes a technique for a double core fiber that converts a mode field diameter of single mode propagation light. That is, as shown in FIG. 10, the core has a double structure composed of a first core 1 at the center and a second core 2 around the core, and the reduced diameter region 3 of the optical fiber having a stepped refractive index profile is formed. Provided. The outer periphery is covered with the cladding layer 4. As a result, in a state where the fiber diameter is reduced in the reduced diameter region 3 and the confinement effect of the central first core 1 is eliminated, the light confinement effect is made to function in the second core 2 around.

  Patent Document 3 describes a laser device that improves the light density by changing the core diameter and bringing the cores closer together without changing the core diameter.

JP 2006-337398 A Japanese Patent Laid-Open No. 3-132605 Japanese Patent No. 3939816

  However, in the technique disclosed in Patent Document 1, the tapered region of the optical fiber concentrator has a multimode structure, and in principle, the light is propagated as the light propagates through this portion. Propagation numerical aperture will increase. And the light which became larger than a core numerical aperture leaks outside from a core, and becomes a loss, and causes the deterioration of transmission efficiency. In the case of the multi-mode structure, the more the light density is focused to improve the light density, the more the light propagation numerical aperture increases in proportion to this, and the transmission efficiency deteriorates. Therefore, it is difficult to achieve both improvement in light density and reduction in transmission efficiency.

  On the other hand, when light propagating in a single mode is used, the core diameter is originally small. Therefore, if the cross-sectional area of the tip of the tapered structure is reduced in order to improve the light density, the core diameter is reduced in the reduced diameter region. Becomes smaller than necessary. For this reason, the propagating light loses the confinement effect of the core light in the middle of the reduced diameter region and becomes leaked light, which causes a decrease in transmission efficiency and a deterioration in beam quality.

  The technique disclosed in Patent Document 2 allows single mode propagation even within a reduced diameter region due to a double core structure, and is applicable to an optical fiber concentrator. However, the light incident on the double core fiber generates a component that couples to the second core due to the characteristic refractive index distribution structure, and this light may propagate in the second core in a multimode. If the second core is designed to have a single-mode propagation structure in the reduced diameter region, for example, if the second core diameter is made small, the multi-mode propagation light as described above increases significantly. On the other hand, if, for example, the second core diameter is made large in order to prevent the generation of multimode propagation light, the second core may be hardly functioning.

  The technique disclosed in Patent Document 3 is to remove a part of the clad of a plurality of optical fibers to which rare earth elements are added so as to have a tapered shape, and to bring the cores close together while keeping the core diameter constant. The light density of the oscillator is improved. Although it is not necessary to take measures against core diameter reduction, it is an ideal structure, but it is difficult to arrange only the cladding of a micron-order thin fiber into a tapered shape and orderly.

  The present invention solves these problems, and an optical fiber type concentrator capable of efficiently condensing light emitted from a laser light source in a single mode, and a high light density using the optical fiber type concentrator, A high beam quality laser apparatus is provided.

  In order to solve the above problems, the present invention provides an input fiber composed of a bundle of a plurality of optical fibers, one end of which is reduced in diameter into a tapered shape, an output fiber composed of an optical fiber having one core, and the input A taper portion fiber formed of a bundle of a plurality of other optical fibers provided between one end of the fiber for output and the output fiber, and the number of the other optical fibers constituting the taper portion fiber is: The number of optical fibers constituting the input fiber is the same as the number of optical fibers, and the diameter or numerical aperture of each of the plurality of other optical fibers constituting the tapered portion fiber constitutes the input fiber. The optical fiber type concentrator is larger than the diameter of each of the plurality of optical fibers or the numerical aperture of the core.

  With such a configuration, the light emitted from the laser light source in the single mode can be efficiently condensed.

  Further, the present invention is the above invention, wherein the taper portion fiber is formed by combining a plurality of taper portion fiber elements composed of a bundle of the plurality of other optical fibers, and the plurality of the plurality of taper portion fiber elements constituting the taper portion fiber element. The diameter of the core or the numerical aperture of each of the other optical fibers is such that the tapered fiber element provided on the side closer to the output fiber has the taper provided on the side closer to the input fiber. The structure is larger than the partial fiber element.

  With such a configuration, it is possible to further suppress the leakage of the laser light in the tapered fiber, so that it is possible to further improve the light density and further suppress the deterioration of the beam quality.

  Further, the present invention is the above invention, wherein the input fiber is composed of a bundle of a plurality of optical fibers each having a core having a different diameter or a core having a different numerical aperture, and the tapered fiber is a core having a different diameter or A bundle of a plurality of the other optical fibers having cores with different numerical apertures is formed.

  With such a configuration, it is possible to efficiently propagate a plurality of lights having different wavelengths.

  Further, the present invention is the above invention, wherein in the above-described invention, the core diameters or numerical apertures of the plurality of optical fibers constituting the input fiber, and the core diameters of the plurality of other optical fibers constituting the tapered fiber. Alternatively, the numerical aperture of the core has a configuration in which the center side is larger than the outside.

  With such a configuration, the light intensity distribution propagating through the optical fiber on the center side of the tapered fiber becomes high, so that the propagating light can be more efficiently propagated to the output fiber.

  Furthermore, the present invention is a laser device including any one of the above optical fiber concentrators.

  According to such a configuration, the light emitted from the laser light source in the single mode is efficiently condensed and propagated to the output fiber, so that it is possible to provide a laser device with high light density and high beam quality.

  According to the above configuration, the present invention can suppress the leakage of laser light in the tapered fiber for condensing light. From this, the outer diameter of the tip of the tapered fiber can be made smaller than before, and the core diameter of the output fiber can be made smaller. Therefore, it is possible to improve the light density and suppress the deterioration of the beam quality. Further, it is not necessary to manufacture an optical fiber having a complicated core structure, and a commercially available fiber can be used.

The block diagram which shows the optical fiber type collector in one embodiment of this invention (A) Sectional view of the optical fiber used in the embodiment (b) Sectional view of the optical fiber used in the output fiber of the embodiment Side view showing the composite fiber of the same embodiment Schematic for explaining the core diameter of the output fiber of the same embodiment (A) Cross-sectional configuration diagram showing the fixing method of the optical fiber type collector of the embodiment (b) Vertical cross-sectional configuration diagram showing the fixing method of the optical fiber type collector of the embodiment (A) Cross-sectional configuration diagram showing another fixing method of the optical fiber type collector according to the embodiment (b) Vertical sectional configuration diagram showing another fixing method of the optical fiber type collector according to the embodiment The block diagram which shows the laser apparatus using the optical fiber type concentrator in one embodiment of this invention Sectional drawing which shows the fiber bundle of the embodiment (A) The figure which shows the laser beam which injects into the output fiber of the embodiment (b) The figure which shows the comparative example of the laser beam which injects into the output fiber of the embodiment Configuration diagram of an optical fiber having a conventional reduced diameter region

  EMBODIMENT OF THE INVENTION The form for implementing this invention is demonstrated referring drawings below.

  FIG. 1 is a block diagram showing an embodiment of an optical fiber type concentrator of the present invention. In FIG. 1, an optical fiber concentrator 10 according to the present embodiment includes an input fiber 11 having one end reduced in a tapered shape, an output fiber 12 formed of an optical fiber having one core, and an input fiber. 11 and a tapered fiber 13 provided between one end of the output fiber 12 and the output fiber 12. The input fiber 11 is composed of a bundle of a plurality of single mode optical fibers 111. The tapered fiber 13 is formed of a bundle of a plurality of other single mode optical fibers 131. The number of other single mode optical fibers 131 constituting the tapered fiber 13 is the same as the number of single mode optical fibers 111 constituting the input fiber 11. Each of the single mode optical fibers 111 constituting the input fiber 11 has a central core 112 and a cladding 113 around the core 112. Each of the other single mode optical fibers 131 constituting the tapered fiber 13 has a central core 132 and a cladding 133 around the core 132. The diameters of the cores 132 of the plurality of other single mode optical fibers 131 constituting the tapered fiber 13 are larger than the diameters of the cores 112 of the plurality of single mode optical fibers 111 constituting the input fiber 11.

  The tapered fiber 13 is configured by combining a first tapered fiber element 13a and a second tapered fiber element 13b, each of which is a bundle of a plurality of other single mode optical fibers 131. The diameters of the cores 132 of the plurality of other single mode optical fibers 131 constituting the tapered fiber elements 13a and 13b are larger in the first tapered fiber element 13a provided on the side closer to the output fiber 12. It is larger than the second tapered fiber element 13b provided on the side close to the input fiber 11.

  In the above configuration, the relationship between the diameter of the core 132 of the other single mode optical fiber 131 and the diameter of the core 112 of the single mode optical fiber 111 may be applied to the numerical aperture relationship of the cores 132 and 112. That is, the following configuration can also be applied.

  The numerical apertures of the respective cores 132 of the plurality of other single mode optical fibers 131 constituting the tapered fiber 13 are larger than the numerical apertures of the respective cores 112 of the plurality of single mode optical fibers 111 constituting the input fiber 11. large. Further, the numerical apertures of the cores 132 of the plurality of other single mode optical fibers 131 constituting the tapered fiber elements 13 a and 13 b are set to the first tapered fiber elements 13 a provided on the side closer to the output fiber 12. Is larger than the second tapered fiber element 13b provided on the side closer to the input fiber 11.

  Alternatively, the diameter and the numerical aperture of each of the cores 132 of the plurality of other single mode optical fibers 131 constituting the tapered fiber 13 are the same as those of the cores 112 of the plurality of single mode optical fibers 111 constituting the input fiber 11. Greater than diameter and numerical aperture. Furthermore, the diameter and numerical aperture of each core 132 of the plurality of other single mode optical fibers 131 constituting the tapered fiber elements 13a and 13b are the first tapered fiber provided on the side close to the output fiber 12. The element 13 a is larger than the second tapered fiber element 13 b provided on the side closer to the input fiber 11.

  That is, at the connection point between the tapered fiber 13 and the input fiber 11 and / or the connection point between the tapered fiber elements 13a and 13b, the output side is at least of the following three relationships compared to the input side: There should be only one relationship. (1) The core diameter is increased, but the core numerical aperture is the same. (2) The core diameter is the same, but the numerical aperture is increased. (3) Both the core diameter and the numerical aperture are increased.

  In FIG. 1, the coating resin formed on the outermost layers of the single mode optical fibers 111 and 131 and the output fiber 12 is omitted.

  Hereinafter, the optical fiber type collector 10 of the present embodiment will be described in detail. The optical fiber concentrator 10 is a fiber in which a plurality of composite fibers 14 in which a single mode optical fiber 111 constituting an input fiber 11 and a single mode optical fiber 131 constituting a tapered fiber 13 are fusion-bonded are bundled. A bundle 15 is provided. Each composite fiber 14 includes cores 112 and 132 and surrounding clads 113 and 133. The taper fiber 13 is formed by fusion-bonding the first taper fiber element 13 a, the second taper fiber element 13 b, and one end of the input fiber 11. The tapered fiber 13 side of the fiber bundle 15 is integrated. A part of the input fiber 11 and the tapered fiber 13 form a tapered diameter-reduced region 16. The distal end portion (the left portion in FIG. 1) of the reduced diameter region 16 is fusion bonded to the end face of the output fiber 12. Therefore, a fusion bonding portion 17 is formed at the coupling portion between the distal end portion of the reduced diameter region 16 and the end face of the output fiber 12. In FIG. 1, for convenience of explanation, the output fiber 12 is shown only in the core 122.

  The core 132 of the single mode optical fiber 131 constituting the tapered fiber 13 in the reduced diameter region 16 has a core diameter equal to or larger than that of the core 112 of the single mode optical fiber 111 constituting the input fiber, or equal to or larger than that. It has a core numerical aperture. Therefore, the single mode light incident on the single mode optical fiber 111 of the optical fiber type concentrator 10 has a small core diameter in the reduced diameter region 16, so that the light confinement effect is weakened. For this reason, the mode field diameter increases and light tends to diverge into the cladding 133. However, in the present embodiment, the tapered fiber 13 is configured by connecting the first tapered fiber element 13a and the second tapered fiber element 13b at an appropriate position in the reduced diameter region 16. Therefore, the light confinement effect can be restored. That is, the diameter of the core of the first tapered fiber element 13a disposed closer to the output fiber 12 is larger than that of the second tapered fiber element 13b disposed closer to the input fiber 11. Or since the numerical aperture of a core is large, the light confinement effect is acquired. Therefore, in the reduced diameter region 16, light can be propagated within the region of the core 132.

  FIG. 2A shows a typical sectional view of an optical fiber used for the composite fiber 14 composed of the single mode optical fiber 111 (131). Quartz glass is used for the core 112 (132) and the clad 113 (133). A coating resin 114 (134) is applied around the cladding 113 (133) to protect the quartz glass. A single mode optical fiber 111 to be connected to an output fiber of a unit laser unit, which will be described later, has a normalized frequency V value V ≦ 2. 405 is satisfied. The better condition is that the single mode optical fiber 111 having the same structure (core diameter, core numerical aperture, cladding diameter, etc.) as the output fiber of the unit laser unit connected to the input end (right side in FIG. 1) of the single mode optical fiber 111 is used. Is to use.

  The tapered fiber 13 compensates for the diameter reduction of the core 112 in the reduced diameter region 16 of the single mode optical fiber 111. For this reason, the reduced diameter size in the reduced diameter region 16 is calculated in advance, and either a single mode optical fiber or a multimode optical fiber may be used. Therefore, an optical fiber having a structure that does not cause leakage light is appropriately selected. In the present embodiment, a multimode optical fiber is used, and a single mode optical fiber that propagates only a single mode light after a step of forming a reduced diameter region described later is used. In this embodiment, the input fiber 11 is composed of a single mode optical fiber 111. However, as described above, only the single mode light propagates through the tapered fiber 13, and therefore the input fiber 11 is not limited to the single mode optical fiber 111.

  The structure of the tapered fiber 13 uses a core 132 having a diameter equal to or larger than that of the core 112 of the single mode optical fiber 111 so that light propagates while maintaining the optical confinement effect. Alternatively, a core 132 (a core 132 having a higher refractive index) having a numerical aperture equal to or greater than that of the core 112 of the single mode optical fiber 111 is used. Although there is no limitation on the diameter of the clad 133, when the diameter of the clad 113 is different from that of the single mode optical fiber 111, the optical fiber on the side with the smaller clad diameter is stretched more than necessary in the melt-stretching process. Care should be taken as it may result in a state of not being done.

  FIG. 2B shows a typical cross-sectional view of an optical fiber used for the output fiber 12. The core 122 uses quartz glass, and the cladding 123 uses quartz glass having a refractive index lower than that of the core 122 or optical resin having a refractive index lower than that of the core 122. When handling a high-power laser, it is preferable to use pure silica glass as the material of the core 122 and quartz glass whose refractive index is lowered by doping fluorine or boron as the material of the cladding 123 in consideration of heat resistance.

  As described above, the present embodiment has a structure in which the diameter of the core 132 or the numerical aperture of the core 132 is gradually increased in the middle portion of the reduced diameter region 16 constituting the tapered fiber 13. Therefore, it is possible to suppress the occurrence of leaked light due to the light confinement effect being reduced by reducing the core diameter of the light incident in the single mode in the reduced diameter region 16. That is, the light incident on the input fiber 11 of the optical fiber concentrator 10 in the single mode is single in the tapered diameter reducing region 16 when the diameter of the fiber bundle 15 in the tip region of the diameter reducing region 16 is small. Since the diameter of the core 132 of the mode optical fiber 131 is also reduced, conventionally, the light confinement effect is weakened, and the mode field diameter is increased (with a broad light intensity distribution) and diverges into the cladding 133. Go. However, in this embodiment, the confinement effect of light is restored by increasing the diameter of the core 132 or the numerical aperture of the core 132 stepwise at an appropriate position of the reduced diameter region 16 constituting the tapered fiber 13. In addition, it is possible to propagate light to the vicinity of the core 132 to the tip of the tapered portion of the reduced diameter region 16. Therefore, the outer diameter of the tip of the reduced diameter region 16 can be made smaller than before. Further, since the light intensity distribution is distributed in the vicinity of the core 132 of the light propagating through each single mode optical fiber 131, the diameter of the core 122 of the output fiber 12 to be connected is the tip of the tapered portion of the reduced diameter region 16 Thus, the entire clad 133 of the fiber bundle 15 need not be included. That is, the diameter of the core 122 of the output fiber 12 may be a diameter that includes all of the vicinity regions of the plurality of cores 132.

  When the inside of the reduced diameter region 16 does not have the structure of the present embodiment, when the diameter of the core 132 becomes small until the light confinement effect disappears, light leaks to the clad 133 and this light propagates in the clad 133. In this case, the diameter of the core 122 of the output fiber 12 to be connected needs to be large enough to include all of the clads 133 of the integrated fiber bundle 15 at the tip of the tapered portion of the reduced diameter region 16. It is. Therefore, since the diameter of the core 122 has to be increased accordingly, the light density is lowered. Furthermore, since the light propagating to the clad 133 becomes multimode propagation, there is a possibility that the propagation numerical aperture is increased and light whose beam quality is worse than the required value is included. In addition, light may be emitted outside the cladding 133 in the reduced diameter region 16 and transmission efficiency may deteriorate.

  The manufacturing method of the optical fiber type concentrator of the present embodiment starts from manufacturing the composite fiber 14 constituting the fiber bundle 15. First, as shown in FIG. 3, the coating resins 114 and 134 on the outer circumferences of the single mode optical fiber 111 constituting the input fiber 11 and the single mode optical fiber 131 constituting the tapered fiber 13 are removed. . At this time, the length for removing the coating resins 114 and 134 is set to be longer than the length in the case of fusion bonding of ordinary optical fibers in advance, in consideration of melt stretching in a later step. When the length to be removed is short, the coating resins 114 and 134 may be melted by the heat of the heating source of the stretching apparatus. In addition, the length from which the coating has been removed is recorded because it is required in the stretching process. In the present embodiment, the single mode optical fiber 131 is prepared as the optical fiber constituting the tapered fiber 13 before the diameter reducing step, but a multimode optical fiber may be prepared.

  Next, as shown in FIG. 3, the single mode optical fiber 111 of the input fiber 11 and the single mode optical fiber 131 of the tapered fiber 13 are fusion-bonded by a commercially available fusion apparatus. The single mode optical fiber 131 constituting the tapered fiber 13 may be connected in series as many as necessary in accordance with the outer diameter of the tip of the reduced diameter region 16. In the present embodiment, two series of the first tapered fiber element 13a and the second tapered fiber element 13b are connected in series. The composite fiber 14 which becomes the diameter-reduced region 16 portion is obtained as described above, and by preparing a plurality of composite fibers 14, preparation for manufacturing the optical fiber concentrator 10 is completed.

  Next, the prepared multiple composite fibers 14 are arranged in parallel in a general drawing apparatus. A plurality of composite fibers 14 are bundled in consideration of increasing the optical density by reducing the diameter of the core 122 of the output fiber 12 because it will be fusion-bonded to the output fiber 12 in a later step. The cross-sectional shape of the fiber bundle 15 is desirably arranged so as to form a close-packed structure. In the longitudinal direction, the distance between the position where the coating is removed and the fusion bonding portion 17 is measured in advance, and the fiber bundle 15 is placed at a position where the effect of the tapered fiber 13 can be obtained based on this distance. Hold it. After the arrangement is completed, the arranged fiber bundles 15 are fused and integrated with a heating source such as a burner, and the softened portion is stretched. By stretching, the outer diameter of the fiber bundle 15 is reduced, and as shown in the enlarged view of FIG. 3, a fiber bundle 15 having a reduced diameter region 16 in the longitudinal direction is obtained. In FIG. 3, only one composite fiber 14 is shown, but the fiber bundle 15 has the same configuration.

  After the drawing is finished, the portion of the minimum cross-sectional area of the integrated fiber bundle 15 is cut and divided by applying a tension. As a result, two fiber bundles 15 having one end reduced in a tapered shape can be formed. In this way, a fiber bundle 15 composed of the single mode optical fiber 111 constituting the input fiber 11 and the single mode optical fiber 131 constituting the tapered fiber 13 is obtained.

  Next, the fiber bundle 15 obtained as described above is coupled to the output fiber 12 via the fusion coupling portion 17. FIG. 4 is a view for explaining the core diameters 122 a and 122 b of the output fiber 12, and is a view showing an end face of the fiber bundle 15. In FIG. 4, seven single mode optical fibers 131 are bundled in the fiber bundle 15, and thereby the tapered fiber 13 is configured. The single mode optical fiber 131 that forms the tapered fiber 13 includes a core 132 and a clad 133. The core diameter of the output fiber 12 when the end face of the fiber bundle 15 and the end face of the output fiber 12 are coupled is the light intensity around each core 132 of the fiber bundle 15 as indicated by the dotted line 122a in FIG. All the high regions should be included. That is, the diameter of the core 122 required for the output fiber 12 when light propagates in the vicinity of each core 132 of the fiber bundle 15 is a portion indicated by a dotted line 122a. This is a diameter that is slightly smaller than the diameter when the entire clad 133 of the fiber bundle 15 is included, and this size is sufficient. That is, it is slightly smaller than the diameter of the core 122 required for the output fiber 12 when the light is also propagated to each clad 133 of the fiber bundle 15 as indicated by a two-dot chain line 122b. Note that the reduced diameter region 16 is originally in a state where the glass is melted and the gap is filled with the surface tension, so that the cross-sectional shape of the single optical fiber is slightly deformed from a circular shape.

For convenience of calculation, assuming that the single optical fiber has a circular cross section, for example, the mode field diameter of the core propagation light at the tip of the tapered portion is φA μm, the clad diameter is φB μm, and seven single mode optical fibers 131 are bundled. State. In this case, the cross-sectional area ratio calculated from the required diameter of the core 122 of the output fiber 12 is as follows.
[No leakage light]: [There leakage ^{light] = [π (2B + A} ) 2/4]: [π (3B) 2/4]

Compared with the case of leaking to the clad 133 of the single mode optical fiber 131, the diameter of the core 122 of the output fiber 12 is reduced to increase the propagating light density by about (3B) ² / (2B + A) ² times. It is possible.

  As described above, the optical fiber type collector 10 in which the fiber bundle 15 and the output fiber 12 are coupled is obtained.

  Finally, in order to increase the mechanical strength of the portion where the coating of the optical fiber type collector 10 is removed, a coating resin is formed on the outer periphery using a fixing jig. FIGS. 5A and 5B are a transverse sectional view and a longitudinal sectional view of a fixing jig for explaining an example of a fixing method of the optical fiber concentrator 10 of the present embodiment. As shown in FIGS. 5 (a) and 5 (b), the optical fiber concentrator 10 obtained as described above is set in the fixing jig 22 having the groove 21, and the entire portion is removed from the coating. A coating resin 23 having a low refractive index is applied to the substrate and cured. As a result, the optical fiber concentrator 10 is stably fixed to the fixing jig 22.

  After that, as shown in FIGS. 5A and 5B, the optical fiber concentrator 10 fixed to the fixing jig 22 is further inserted into a metal cylinder 24 or the like, and both end portions of the cylinder 24 are inserted. May be covered with a resin 25 together with the single mode optical fiber 131 and the output fiber 12, and the inside of the tube 24 may be sealed. As a result, the optical fiber concentrator 10 is stably fixed by the fixing jig 22.

  As another fixing method, as shown in FIGS. 6A and 6B, the coating resin is not applied to the portion where the coating of the optical fiber concentrator 10 is removed, and the glass portion is exposed. There is also a method in which only one point each of the fiber bundle 15 of the single mode optical fiber 131 and the covering portion of the output fiber 12 is fixed to the fixing jig 22 with the coating resin 23. Also in this case, as shown in FIGS. 6A and 6B, a structure in which the inside of the cylinder 24 is sealed using a metal cylinder 24 or the like may be used.

  FIG. 7 is a block diagram showing an embodiment of the laser apparatus of the present invention. The optical fiber type concentrator 10 manufactured as described above is attached to the laser device 40 as shown in FIG. In FIG. 7, the single mode optical fiber 111 (only three are shown in FIG. 7) constituting the input fiber 11 of the optical fiber type collector 10 has three single mode outputs each serving as a laser light source. The unit laser unit 41 is connected. Each single mode optical fiber 111 is connected to an output fiber 411 provided in the unit laser unit 41 by a fusion bonding part 412. The output fiber 12 of the optical fiber concentrator 10 is connected to the transmission fiber 42 by a fusion-bonding portion 422. As a result, the laser light emitted from each unit laser unit 41 is condensed onto one transmission fiber 42 via the optical fiber concentrator 10. The output end of the transmission fiber 42 can be used, for example, to connect to the welding head 43 or the like and weld the workpiece 44 by utilizing the high density and high output characteristics. In FIG. 7, one laser unit 413 is composed of three unit laser units 41, but the laser unit 413 is composed of arbitrary N unit laser units 41.

  Each unit laser unit 41 may not have the same specification. For example, in addition to light having a wavelength of 1.06 μm, light having a wavelength of 0.97 μm, 0.64 μm, etc. may be emitted simultaneously. In this case, as shown in FIG. 8, the single-mode optical fiber 111 constituting the input fiber 11 and the single-mode optical fiber 131 constituting the tapered fiber 13 used for the fiber bundle 15 are propagated at their respective wavelengths. Incorporate what matches. In addition, when the tip of the diameter-reduced region 16 of the fiber bundle 15 is further extended to make the core interval closer, a light transfer phenomenon occurs between the cores as in an optical fiber coupler used in an optical amplifier. It becomes easy. By utilizing this, an optical fiber having a strong light confinement effect may be arranged from the outside of the array of the fiber bundle 15 toward the center, and the light intensity distribution at the center of the fiber bundle 15 may be increased.

  That is, the input fiber 11 is composed of a bundle of a plurality of single mode optical fibers 111 having cores 112 having different diameters, and the tapered fiber 13 is a plurality of other single mode optical fibers 131 having cores 132 having different diameters. You may be comprised from a bundle of. In this case, the same effect can be obtained even if the relationship between the diameters of the core 112 and the core 132 is the relationship between the numerical apertures of the core 112 and the core 132. That is, the input fiber 11 is composed of a bundle of a plurality of single mode optical fibers 111 having cores 112 with different numerical apertures, and the tapered fiber 13 is a plurality of other single mode lights having cores 132 with different numerical apertures. It may be composed of a bundle of fibers 131.

  In FIG. 8, the diameter of the core 112a (132a) of the single mode optical fiber 111a (131a), the diameter of the core 112b (132b) of the single mode optical fiber 111b (131b), and the core of the single mode optical fiber 111c (131c). The diameter of 112c (132c) is different from each other.

  Further, the diameter of the core 112 of the plurality of single mode optical fibers 111 constituting the input fiber 11 and the diameter of the core 132 of the plurality of other single mode optical fibers 131 constituting the taper portion fiber 13 are May be larger than the outside. Also in this case, the same effect can be obtained by using the relationship between the diameters of the core 112 and the core 132 as the relationship between the numerical apertures of the core 112 and the core 132. That is, the numerical apertures of the cores 112 of the plurality of single mode optical fibers 111 constituting the input fiber 11 and the numerical apertures of the cores 132 of the plurality of other single mode optical fibers 131 constituting the tapered fiber 13 are the center side. The configuration may be larger than the outside.

  In FIG. 8, the diameter of the core 112b (132b) of the single mode optical fiber 111b (131b) disposed in the middle is larger than the diameter of the core 112a (132a) of the single mode optical fiber 111a (131a) disposed at the outermost periphery. Is bigger. Furthermore, the diameter of the core 112c (132c) of the single mode optical fiber 111c (131c) arranged at the center is larger than the diameter of the core 112b (132b) of the single mode optical fiber 111b (131b) arranged in the middle. Is bigger.

  Although the specific example of this Embodiment is demonstrated below, the following specific example is only a mere illustration of this invention, and does not limit this invention.

The optical fibers used when manufacturing the optical fiber concentrator 10 shown in FIG. 1 are as follows.
Single mode optical fiber 111 constituting input fiber 11: core diameter φ4 μm, clad diameter φ125 μm, core numerical aperture 0.12
Single mode optical fiber 131 constituting tapered fiber 13: core diameter φ9 μm, clad diameter φ125 μm, core numerical aperture 0.13
Output fiber 12: core diameter φ100 μm, cladding material: low refractive index resin, core numerical aperture 0.46

  First, the single-mode optical fiber 111 constituting the input fiber 11 and the single-mode optical fiber 131 constituting the tapered fiber 13 were fusion-bonded to produce six composite fibers 14. In addition, an optical fiber composed of only one single mode optical fiber 111 was prepared. These seven optical fibers were bundled so as to form a close-packed arrangement (six composite fibers 14 were arranged so as to surround one optical fiber in the center), and were fused and integrated by a heater. Thereafter, the single-mode optical fiber 111 as a single unit was stretched until the minimum cladding diameter was from φ125 μm to about φ30 μm. After the fiber bundle 15 was split into two at the minimum portion, it was fusion-bonded to the output fiber 12. Thereafter, a coating resin having a refractive index lower than that of glass was applied again to the portion where the coating was removed to protect the glass portion, and the optical fiber type collector 10 was completed.

  For verification, a laser light source was connected to the optical fiber concentrator 10 and the state of the output light was observed (this measurement was performed before the output fiber 12 was fusion-bonded). The laser light source has an oscillation wavelength of 1.06 μm and an output of 10 mW. Laser light was incident on one end of each of the input fiber 11 welded with the tapered fiber 13 and the input fiber 11 not welded with the tapered fiber 13, and the shape of the laser light emitted from the other end was observed. . This observation is performed before the output fiber 12 is fusion-bonded.

  FIG. 9A shows the shape of the laser beam emitted from the tip of the tapered fiber 13 in the present embodiment. FIG. 9B shows the shape of the laser light emitted from the tip of the input fiber 11 where the tapered fiber 13 is not fused. In either case, the emitted laser light is distributed in the vicinity of the core as shown in FIGS. 9 (a) and 9 (b). However, when the tapered fiber 13 is fused, the mode field diameter is smaller than when it is not fused, and the light intensity distribution is not broad. From this result, the cross-sectional area required for the core 122 of the output fiber 12 when the tapered fiber 13 is fused is approximately equal to the cross-sectional area when the tapered fiber 13 is not fused. It was confirmed that it can be made 1.3 times smaller. Further, when the respective output values were confirmed with the output fiber 12 coupled, the same output was obtained.

  As described above, the optical fiber concentrator of the present invention is composed of an input fiber composed of a bundle of a plurality of single mode optical fibers, one end of which is reduced in taper shape, and an optical fiber having one core. An output fiber, and a tapered fiber formed of a bundle of a plurality of other optical fibers provided between one end of the input fiber and the output fiber, and the other optical fibers constituting the tapered fiber The number is the same as the number of single-mode optical fibers that make up the input fiber, and the core diameter or core numerical aperture of each of the other optical fibers that make up the tapered fiber forms the input fiber. Each of the plurality of single mode optical fibers has a configuration larger than the diameter of the core or the numerical aperture of the core.

  With such a configuration, it is possible to suppress the leakage of laser light through the tapered fiber for condensing light. From this, the outer diameter of the fiber bundle tip can be made smaller than before, and the core diameter of the output fiber can be made smaller. Therefore, it is possible to improve the light density and suppress the deterioration of the beam quality. Further, it is not necessary to manufacture a fiber having a complicated core structure, and a commercially available fiber can also be used.

  In the present invention, the tapered fiber is configured by combining a plurality of tapered fiber elements each composed of a bundle of a plurality of other optical fibers, and each of the plurality of other optical fibers constituting the tapered fiber element. The diameter of the core or the numerical aperture of the core has a configuration in which the tapered fiber element provided on the side close to the output fiber is larger than the tapered fiber element provided on the side close to the input fiber.

  With such a configuration, it is possible to further suppress the leakage of laser light through the tapered fiber. From this, the outer diameter of the fiber bundle tip can be further reduced, and the core diameter of the output fiber can be further reduced. Therefore, it is possible to further improve the light density and further suppress the beam quality deterioration.

  In the present invention, the input fiber is composed of a bundle of a plurality of optical fibers each having a core having a different diameter or a core having a different numerical aperture, and the tapered fiber has a core having a different diameter or a core having a different numerical aperture. It is composed of a bundle of a plurality of other optical fibers.

  With such a configuration, an input fiber can be configured with a plurality of optical fibers that match the propagation characteristics of the wavelengths of the plurality of unit laser units that emit light of different wavelengths. Therefore, by connecting a plurality of unit laser units that emit light of different wavelengths to a plurality of optical fibers that match the propagation characteristics of the wavelengths, it is possible to efficiently propagate a plurality of lights having different wavelengths. .

  In the present invention, the core diameter or core numerical aperture of the plurality of optical fibers constituting the input fiber, and the core diameter or core numerical aperture of the other optical fibers constituting the tapered fiber are: The center side has a larger configuration than the outside.

  With such a configuration, when the tip of the taper portion fiber is further extended to approach the core interval, light is transferred between the cores and propagates through the optical fiber on the center side of the taper portion fiber. Since the light intensity distribution becomes high, the propagating light can be efficiently propagated to the output fiber.

  Furthermore, the present invention is a laser device including any one of the above optical fiber concentrators.

  According to such a configuration, the light emitted from the laser light source in the single mode is efficiently condensed and propagated to the output fiber, so that it is possible to provide a laser device with high light density and high beam quality.

  The optical fiber type concentrator of the present invention is capable of condensing light on a single optical fiber at a high light density, and can suppress deterioration in beam quality, so that it is useful for a laser device with high output and high beam quality. It is.

DESCRIPTION OF SYMBOLS 10 Optical fiber type collector 11 Input fiber 12 Output fiber 13 Tapered fiber 13a, 13b Tapered fiber element 14 Composite fiber 15 Fiber bundle 16 Reduced diameter region 17, 412, 422 Fusion joint 21 Groove 22 Fixed treatment Tool 23, 114, 134 Coating resin 24 Tube 25 Resin 40 Laser device 41 Unit laser unit 42 Transmission fiber 43 Welding head 44 Workpiece 111, 111a, 111b, 111c, 131, 131a, 131b, 131c Single mode optical fiber 112, 112a , 112b, 112c, 122, 132, 132a, 132b, 132c Core 113, 123, 133 Clad 122a, 122b Core diameter 411 Output fiber 413 Laser unit

Claims (5)

An input fiber composed of a bundle of a plurality of optical fibers, one end of which is reduced in taper shape, an output fiber composed of an optical fiber having one core, and between one end of the input fiber and the output fiber A taper portion fiber formed of a bundle of a plurality of other optical fibers, the diameter of the output fiber side of which is smaller than that of the input fiber side, and constituting the taper portion fiber. The number of the other optical fibers is the same as the number of the optical fibers constituting the input fiber, and the diameter or the numerical aperture of the core of each of the plurality of other optical fibers constituting the tapered fiber. Is an optical fiber type concentrator that is larger than the core diameter or the numerical aperture of each of the plurality of optical fibers constituting the input fiber. The taper portion fiber is configured by combining a plurality of taper portion fiber elements including a bundle of the plurality of other optical fibers, and each of the cores of the plurality of other optical fibers constituting the taper portion fiber element. The diameter or the numerical aperture of the core is larger in the tapered fiber element provided on the side closer to the output fiber than in the tapered fiber element provided on the side closer to the input fiber. The optical fiber type concentrator described. The input fiber is composed of a bundle of a plurality of optical fibers having cores with different diameters or cores with different numerical apertures, and the tapered fiber has a plurality of cores with different diameters or cores with different numerical apertures. 2. The optical fiber type concentrator according to claim 1, wherein the optical fiber type concentrator is composed of a bundle of other optical fibers. The core diameter or the numerical aperture of the plurality of optical fibers constituting the input fiber, and the core diameter or the numerical aperture of the plurality of other optical fibers constituting the tapered portion fiber are the center side. The optical fiber type concentrator according to claim 3, wherein is larger than the outside. A laser apparatus comprising the optical fiber type concentrator according to any one of claims 1 to 4.

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