JP2012212775A - Capillary, combiner using the same, and combiner manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capillary capable of obtaining a combiner capable of reducing an optical loss, and the combiner using the same and a combiner manufacturing method.SOLUTION: A capillary 40 has a plurality of through holes 41, 42 along a longer direction. In a predetermined range from the center on a plane vertical to the longer direction, a particular chemical element which absorbs a laser beam having a particular wavelength transmitting through glass is added with higher concentration than outside the predetermined range.

Description

  The present invention relates to a capillary capable of realizing a combiner capable of reducing light loss, a combiner using the same, and a method of manufacturing the combiner.

  A fiber laser device using an optical fiber for amplification has excellent light condensing performance, a small beam spot with high power density can be obtained, and non-contact processing is possible. Used in various fields. In particular, the output of fiber laser devices used in the processing field and the medical field has been increased.

  An amplification optical fiber used in a fiber laser device includes a core to which an active element is added and a clad that covers an outer peripheral surface of the core. The pumping light propagating through the cladding of the amplifying optical fiber is absorbed by the active element, so that the active element is brought into an excited state, and the amplified element is propagated through the core by stimulated emission of the activated element in the excited state. The light is amplified and emitted. As a system for injecting pump light into the cladding, there is an end pump system in which pump light is incident from the end face of the amplification optical fiber. In this system, a plurality of pump fibers generally connected to the end face of the amplification optical fiber are used. Then, excitation light is incident on the amplification optical fiber. When a plurality of optical fibers such as this excitation fiber are connected to one optical fiber, a capillary in which a plurality of through holes are formed in a cylindrical glass may be used to accurately align the positions of the plurality of optical fibers. is there.

  Patent Document 1 below describes a combiner using such a capillary. This combiner is manufactured as follows. First, an optical fiber is inserted into each of the plurality of through holes of the capillary. Then, the capillary with the optical fiber inserted into the through hole is heated and melted using a flame torch or the like, and the inserted optical fiber and capillary are integrated. Next, each optical fiber integrated with the capillary is end-connected together with the capillary to an optical fiber such as a multi-core fiber.

JP 2008-277582 A

  In the manufacturing process of the combiner, if the optical fiber inserted into the capillary is distorted when the capillary is heated, there is a risk of light loss. For this reason, it is better that the optical fiber is not heated excessively.

  However, when the capillary is heated with a flame or the like as described above, the capillary is heated from the side surface direction. At this time, the side close to the flame tends to be easily heated, and the side far from the flame tends to be difficult to be heated. Therefore, if the capillary is heated in order to properly integrate the optical fiber far from the flame with the capillary, the optical fiber on the side close to the flame is excessively heated, and the outer peripheral surface of the optical fiber may be distorted. . In such an optical fiber having a distorted outer peripheral surface, there is a risk of causing light loss as described above.

  Therefore, an object of the present invention is to provide a capillary capable of realizing a combiner capable of reducing light loss, a combiner using the capillary, and a method of manufacturing the combiner.

  In order to solve the above-mentioned problems, the present inventor has studied a method of heating a capillary with laser light. Specifically, a specific element that absorbs a laser beam having a specific wavelength that passes through the glass is uniformly added to the glass used for the capillary, and the capillary is irradiated with the laser beam having the specific wavelength to heat the capillary. It is to do. Thus, it was considered that the above problems could be solved. However, it has been found that such a method of heating a capillary tends to be excessively heated on the side of the capillary irradiated with laser light, as in the method of heating with a flame. Therefore, the present inventor has further studied earnestly and has come to make the present invention.

  That is, the capillary of the present invention has a plurality of through holes formed along the longitudinal direction, and absorbs laser light having a specific wavelength that passes through the glass within a predetermined range from the center of the plane perpendicular to the longitudinal direction. The specific element is added at a concentration higher than outside the predetermined range.

  By irradiating laser light of a specific wavelength with an optical fiber inserted into such a capillary, a specific element added to a predetermined range from the center of the capillary absorbs the laser light and generates heat, The capillary and the optical fiber can be integrated. At this time, the capillary generates heat on the center side, and this heat is conducted from the center side toward the outer peripheral side. Therefore, the temperature difference between the laser beam irradiation side of the capillary and the laser beam irradiation side and the opposite side can be suppressed, and the capillary can be heated as a whole. For this reason, it can prevent that the one part optical fiber inserted in the through-hole of a capillary is overheated, and an outer peripheral surface is distorted. Therefore, by using such a capillary, it is possible to realize a combiner that can reduce the loss of light.

  Furthermore, it is preferable that the additive concentration of the element is gradually increased from the outer peripheral side to the center side in a plane perpendicular to the longitudinal direction.

  By adding the element in this way, the absorption efficiency of the laser beam becomes higher toward the center side. Therefore, when laser light is irradiated from the side surface of the capillary, even if the intensity of the laser light becomes weak before the laser light reaches the center of the capillary by being absorbed by the element, the center side of the capillary Can generate heat. Therefore, the outer peripheral side and the center side can be balanced so as to generate heat appropriately within a predetermined range in which an element that absorbs laser light is added.

  Such an addition concentration may be gradually increased stepwise from the outer peripheral side to the center side, or may be gradually increased with a gentle gradient.

  Moreover, it is preferable that the specific element is not added to the outer peripheral side of the predetermined range.

  By not adding an element that absorbs laser light to the outer peripheral side of the capillary, it is possible to prevent the laser light from being absorbed on the outer peripheral side.

  A second specific element that absorbs a second laser beam having a wavelength different from the laser beam having the specific wavelength may be added to the outer peripheral side of the predetermined range.

  In the capillary having such a configuration, the entire capillary can be further heated by heating the outer peripheral side with the second laser beam.

  The combiner of the present invention has a plurality of through holes formed along the longitudinal direction, and absorbs laser light having a specific wavelength that passes through the glass within a predetermined range from the center in a plane perpendicular to the longitudinal direction. A capillary in which a specific element is added at a concentration higher than outside the predetermined range; a plurality of optical fibers that are inserted into the through-holes of the capillary and integrated with the capillary; and A capillary and another optical fiber to which end faces of the plurality of optical fibers are connected.

  Such a combiner can prevent a part of the optical fiber in which the capillary is inserted into the through hole from being excessively heated and distort the outer peripheral surface, so that the loss of light can be reduced.

  In the method for manufacturing a combiner according to the present invention, a plurality of through holes are formed along the longitudinal direction, and a laser beam having a specific wavelength that transmits through the glass within a predetermined range from the center in a plane perpendicular to the longitudinal direction. An insertion step of inserting an optical fiber into each through-hole of the capillary to which a specific element that absorbs is added at a concentration higher than outside the predetermined range, and the specific wavelength from the side surface direction of the capillary An integration step of irradiating laser light to heat the capillaries to integrate the optical fibers and the capillaries, and connect the capillaries and end faces of the optical fibers to other optical fibers. A connecting step.

  According to such a combiner manufacturing method, heat can be generated from the center side of the capillary as described above, whereby the capillary can be heated as a whole, and some of the optical fibers inserted into the through-holes of the capillary can be heated. It is possible to prevent the outer peripheral surface from being distorted due to excessive heating. Therefore, by using such a capillary, it is possible to realize a combiner that can reduce the loss of light.

  Further, the laser beam having the specific wavelength is preferably emitted from a plurality of directions different from each other. In this case, the capillary can be further heated as a whole.

  In addition, a second specific element that absorbs a second laser beam having a wavelength different from the laser beam having the specific wavelength is added to a range on the outer peripheral side of the predetermined range in the capillary, In the integration step, it is preferable to further irradiate the second laser beam from the side surface direction of the capillary to heat the capillary.

  By heating the outer peripheral side in addition to the center side with the second laser light, the entire capillary can be further heated. Therefore, it is possible to further suppress the excessive heating of some of the optical fibers inserted into the through holes of the capillary.

  Furthermore, it is preferable that the second laser light is irradiated from a plurality of different directions. In this case, the capillary can be further heated as a whole.

  As described above, according to the present invention, a capillary capable of realizing a combiner capable of reducing light loss, a combiner using the capillary, and a method of manufacturing the combiner are provided.

It is a figure which shows the fiber laser apparatus using the combiner which concerns on 1st Embodiment of this invention. It is a figure which shows the structure in a cross section perpendicular | vertical to the longitudinal direction of the optical fiber for amplification shown in FIG. It is a figure which shows the combiner of FIG. It is a figure which shows the mode of the structure in a cross section perpendicular | vertical to the longitudinal direction of the combiner of FIG. It is a figure which shows the mode of the capillary of FIG. It is a flowchart which shows the manufacturing process of a combiner. It is a figure which shows the mode after an insertion process. It is a figure which shows the mode of an integration process. It is a figure which shows the mode of the capillary used for the combiner which concerns on 2nd Embodiment of this invention. It is a figure which shows the mode of the capillary used for the combiner which concerns on 3rd Embodiment of this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a capillary according to the present invention, a combiner using the capillary, and a method for manufacturing the combiner will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing a fiber laser device 1 using a combiner according to a first embodiment of the present invention.

  As shown in FIG. 1, a fiber laser apparatus 1 includes a seed light source 10 that outputs seed light and an optical fiber amplifier 2 as main components, and is an MO-PA (Master Oscillator Power Amplifier) type fiber laser. It is considered as a device.

  The seed light source 10 is composed of, for example, a laser light source composed of a laser diode, or a Fabry-Perot type or fiber ring type fiber laser device. The seed light output from the seed light source 10 may be called signal light, but the signal is not particularly superimposed on the seed light. The seed light source 10 is connected to the seed optical fiber 15. Therefore, the seed light output from the seed light source 10 propagates through the seed optical fiber 15.

  The optical fiber amplifier 2 also includes a pumping light source 20 that outputs pumping light, an amplifying optical fiber 30, seed light that is output from the seed light source 10, and pumping light that is output from the pumping light source 20. A combiner 3 for inputting to the fiber 30 is provided as a main configuration.

  The excitation light source 20 is composed of a plurality of laser diodes (LD) 21. In addition, excitation fibers 25 are connected to the excitation light sources 20, respectively. Accordingly, the pumping light output from each LD 21 propagates through the pumping fiber 25.

  FIG. 2 is a diagram showing a structure in a cross section perpendicular to the longitudinal direction of the amplification optical fiber 30 shown in FIG. As shown in FIG. 2, the amplification optical fiber 30 is a double-clad fiber including a core 36, a clad 37 that covers the core 36, and a resin clad 38 that covers the clad 37. The refractive index of the clad 37 is lower than the refractive index of the core 36, and the refractive index of the resin clad 38 is further lower than the refractive index of the clad 37. The core 36 has a diameter of, for example, 28 μm, the cladding 37 has an outer diameter of, for example, 400 μm, and the resin cladding 38 has an outer diameter of, for example, 450 μm.

  Moreover, as a material which comprises the core 36, the glass (quartz) to which active elements, such as ytterbium (Yb) which are made into an excited state by the excitation light output from the excitation light source 20, was added, for example is mentioned. Examples of such active elements include rare earth elements, and examples of rare earth elements include thulium (Tm), cerium (Ce), neodymium (Nd), europium (Eu), and erbium (Er) in addition to Yb. Can be mentioned. In addition to rare earth elements, active elements include bismuth (Bi), chromium (Cr), and the like. In addition, an element such as germanium that increases the refractive index of the core 36 is added to the glass constituting the core 36 as necessary. Further, as a material constituting the clad 37, when an element for increasing the refractive index is added to the glass constituting the core 36, for example, a glass to which no dopant is added is cited. When the element which raises a refractive index is not added to the glass which comprises, the glass with which dopants, such as a fluorine which reduces a refractive index, were added is mentioned. Moreover, as a material which comprises a resin clad, ultraviolet curable resin is mentioned, for example.

  When Yb is added as a dopant to the core 36 of the amplification optical fiber 30 as described above, the seed light output from the seed light source 10 is not particularly limited, but the wavelength Is a laser beam with a wavelength of 1080 nm, and the excitation light output from each LD 21 is not particularly limited, but is a laser beam with a wavelength of 910 nm, for example.

  3 is a diagram showing the combiner 3 of FIG. 1, and FIG. 4 is a diagram showing a structure in a cross section perpendicular to the longitudinal direction of the combiner 3 of FIG. As shown in FIGS. 3 and 4, the combiner 3 includes a capillary 40 in which a through-hole 41 and a plurality of through-holes 42 are formed, a seed optical fiber 15 inserted into the through-hole 41 of the capillary 40, and each through-hole. The excitation fiber 25 inserted into the hole 42 and the bridge fiber 50 connected to the end face of the capillary 40 are mainly provided. In FIG. 3, for easy understanding, the capillary 40, the bridge fiber 50, and the amplification optical fiber 30 are shown apart from each other.

  The capillary 40 has a cylindrical outer shape, and a through hole 41 penetrating from one end face 43 to the other end face 44 is formed along the longitudinal direction at the center in the radial direction. The same number of through-holes 42 as the excitation fibers 25 are formed along the longitudinal direction from one end face 43 to the other end face 44 so as to surround. The diameter of the capillary 40 is not particularly limited as long as the through holes 41 and 42 having a necessary diameter can be formed.

  The end of the seed optical fiber 15 opposite to the side connected to the seed light source 10 is inserted into the through-hole 41 of the capillary 40 from one end face 43 to the other end face 44, and the respective excitation fibers 25. The end of the side opposite to the side connected to the excitation light source 20 is inserted into each through hole 42 from one end surface 43 to the other end surface 44. Further, in this state, the through holes 41 and 42 are collapsed, and the seed optical fiber 15 and the respective excitation fibers 25 and the capillary 40 are integrated. In the state where the seed optical fiber 15 and the respective excitation fibers 25 and the capillary 40 are integrated, the outer peripheral surface of the seed optical fiber 15 and the outer peripheral surface of the excitation fiber 25 in the capillary 40 are suppressed from being distorted. .

  As shown in FIGS. 3 and 4, the seed optical fiber 15 includes a core 16 and a clad 17 that covers the core 16, and is, for example, a single mode fiber. The refractive index of the clad 17 is set lower than that of the core 16. The diameter of the core 16 is 4 μm, for example, and the outer diameter of the clad 17 is 125 μm, for example. Moreover, as a material which comprises the core 16 of the seed optical fiber 15, the glass which added germanium is mentioned, for example, As a material which comprises the clad 17, the glass without an additive is mentioned, for example.

  The number of pumping fibers 25 is the same as the number of LDs 21 of the pumping light source 20, and each pumping fiber 25 has a core 26 and a clad 27 that covers the core 26, and is, for example, a multimode fiber. The The refractive index of the cladding 27 of each pump fiber 25 is set lower than the refractive index of the core 26. The diameter of the core 26 of each pump fiber 25 is, for example, 105 μm, and the outer diameter of the cladding 27 is, for example, 125 μm. Moreover, as a material which comprises the core 26 of each excitation fiber 25, the glass to which no dopant is added is mentioned, for example, As a material which comprises the clad 27, the glass to which fluorine was added, for example is mentioned. Can be mentioned.

  The capillary 40 is made of glass (quartz). The refractive index of the capillary 40 is preferably lower than the refractive index of the cladding 17 of the seed optical fiber 15. With this configuration, it is possible to prevent light propagating through the cladding 17 of the seed optical fiber 15 from propagating to the capillary 40. For this configuration, for example, the clad 17 of the seed optical fiber 15 may be made of glass to which no dopant is added, and the capillary 40 may be made of glass to which fluorine is added. Alternatively, the refractive index of the capillary 40 is preferably equal to the refractive index of the cladding 17 of the seed optical fiber 15 and higher than the refractive index of the cladding 27 of the excitation fiber 25. With this configuration, light propagating in the cladding 17 of the seed optical fiber 15 may propagate to the capillary 40, but this light can be prevented from propagating to the cladding 27 of the excitation fiber 25. . For this configuration, for example, the cladding 17 of the seed optical fiber 15 and the capillary 40 are made of glass to which no dopant is added, and the cladding 27 of the excitation fiber 25 is made of glass to which fluorine is added. Just do it.

  5 is a diagram showing the state of the capillary of FIG. 4, and specifically, FIG. 5A is a diagram showing the state of the cross-section structure perpendicular to the longitudinal direction of the capillary 40, and FIG. ) Is a diagram showing a state of concentration distribution of a specific element added to the capillary 40.

A specific element that absorbs laser light having a specific wavelength that passes through the glass constituting the capillary 40 is added to the capillary 40. For ease of understanding, in FIG. 5B, a concentration distribution at a specific limit is shown on the assumption that the through hole 42 is not formed. As shown in FIG. 5, this specific element is added at a constant concentration in a region AR _i that is within a predetermined range from the center in a plane perpendicular to the longitudinal direction of the capillary 40. Note that, as indicated by a broken line in FIG. 5A, the area AR _i of the present embodiment is slightly outside the through hole 42. And, in the area AR _o in the range of the outer circumferential side of the area AR _i of the capillary 40, this particular element is not added. In the present embodiment, samarium (Sm) is added to the capillary 40 as a specific element. Samarium absorbs laser light having a wavelength of 1064 nm, and the laser light having this wavelength passes through the glass constituting the capillary.

  As shown in FIG. 3, the bridge fiber 50 has a core 56 provided at the center in the radial direction and a clad 58 covering the core 56, and the outer diameter of one end is reduced. It is a tapered fiber. Specifically, the side of the bridge fiber 50 connected to the end face of the capillary 40 has the same outer diameter as that of the capillary 40, and the outer shape is gradually reduced from the middle, so that the side opposite to the capillary 40 side is maintained. The end portion is most reduced in diameter. The diameter of the bridge fiber 50 on the capillary 40 side is the same as the diameter of the capillary 40, and the opposite side to the capillary 40 side is the same as the cladding 37 of the amplification optical fiber 30.

  The refractive index of the cladding 58 is set lower than the refractive index of the core 56. Examples of the material of the core 56 include glass to which germanium is added, and examples of the material constituting the clad 58 include glass having no additive.

  And the core 16 of the seed optical fiber 15 and the core 56 of the bridge fiber 50 are connected by connecting the end surface 51 of the bridge fiber 50 on the non-reduced side and the other end surface 44 of the capillary 40. The core 26 of each excitation fiber 25 and the clad 58 of the bridge fiber 50 are connected. Thus, the combiner 3 is configured.

  Further, in the combiner 3, the end face 52 of the bridge fiber 50 whose diameter is reduced and the one end face of the amplification optical fiber 30 are connected, and the core 56 of the bridge fiber 50 and the core 36 of the amplification optical fiber 30 are connected. Are connected, and the cladding 58 of the bridge fiber 50 and the cladding 37 of the amplification optical fiber 30 are connected. Thus, the core 16 of the seed optical fiber 15 and the core 36 of the amplification optical fiber 30 are coupled via the bridge fiber 50, and the core 26 of the excitation fiber 25 and the clad 37 of the amplification optical fiber 30 are coupled. .

  Such a fiber laser device 1 operates as follows.

  First, excitation light is output from the plurality of LDs 21 of the excitation light source 20. As described above, the output excitation light has a wavelength of 910 nm, for example. The pumping light output from each LD 21 propagates through each pumping fiber 25 and is input to the clad 58 from the end surface 51 of the bridge fiber 50 on the non-reduced side in the combiner 3. At this time, as described above, since the distortion of the outer peripheral surface of each excitation fiber 25 in the capillary 40 is suppressed, loss of excitation light in the combiner 3 is suppressed. Then, the light is input from the clad 58 to the clad 37 of the amplification optical fiber 30 and propagates mainly through the clad 37.

  Also, seed light is output from the seed light source 10. The output seed light has a wavelength of, for example, 1080 nm as described above. Then, the seed light propagates through the core 16 of the seed optical fiber 15 and enters the core 56 of the bridge fiber 50 in the combiner 3. At this time, as described above, since the distortion of the outer peripheral surface of the seed optical fiber 15 in the capillary 40 is suppressed, the loss of seed light in the combiner 3 is suppressed. The seed light is input from the core 56 of the bridge fiber 50 to the core 36 of the amplification optical fiber 30 and propagates through the core 36.

  Then, in the amplification optical fiber 30, when the excitation light propagating through the cladding 37 passes through the core 36, the active element added to the core 36 is set to the excited state, and the stimulated emission of the active element in the excited state is performed. The seed light propagating through the core 36 is amplified. Thus, the amplified seed light is output from the amplification optical fiber 30 as output light.

  In such a fiber laser device 1, as described above, in the combiner 3, the outer peripheral surfaces of the seed optical fiber 15 and the pump fiber 25 are not distorted, and the loss of the seed light and the pump light is small. Therefore, efficient light amplification is performed, and output light with high power can be obtained.

  Next, the manufacturing method of the combiner 3 is demonstrated.

  FIG. 6 is a flowchart showing the manufacturing process of the combiner 3. As shown in FIG. 6, the combiner 3 of this embodiment includes a preparation process P <b> 1 for preparing the capillary 40, the seed optical fiber 15, the excitation fiber 25, and the bridge fiber 50, and the respective through holes 41 of the capillary 40. 42, the seed optical fiber 15 and the excitation fiber 25 are inserted into the insertion step P2, and laser light of a specific wavelength is irradiated from the side surface direction of the capillary 40 to heat the capillary 40, and the seed optical fiber 15 and the respective An integration step P3 for integrating the excitation fiber 25 and the capillary 40, and a connection step P4 for connecting the capillary 40, the seed optical fiber 15, and the respective excitation fibers 25 to the bridge fiber are provided.

<Preparation process P1>
A capillary 40 is prepared. For example, the capillary 40 is prepared as follows. First, a first glass tube comprising an outer circumferential side of the area AR _o than the area AR _i shown in FIG. 5 (A). A specific element (samarium in the present embodiment) is not added to the first glass tube. Next, the second glass tube having an outer diameter slightly smaller than the inner diameter of the first glass tube and having a through hole corresponding to the through hole 41 is inserted into the through hole of the first glass tube. A specific element is uniformly added to the glass constituting the second glass tube at the concentration shown in FIG. Next, the first glass tube and the second glass tube are integrated by collapsing while applying a predetermined pressure to the through hole of the second glass tube. At this time, a through hole corresponding to the through hole 41 is formed at the center of the integrated glass body in the radial direction. A plurality of through holes are formed so as to correspond to the through holes 42 so as to surround the through holes. This through hole is formed using a drill or the like, and then the inner wall surface may be polished. In this way, a base material that becomes the capillary 40 is obtained. In the base material of the capillary 40, a specific element is uniformly added in a predetermined range from the center. When fluorine is added to the glass constituting the capillary 40, fluorine is added to the entire glass constituting the base material that becomes the capillary 40.

  Next, it heats, applying a predetermined pressure in each through-hole of this base material, and draws a base material. Then, the drawn glass body is cut into a predetermined length to obtain the capillary 40 shown in FIG.

  Further, a seed optical fiber 15 and a pump fiber 25 are prepared. The seed optical fiber 15 and the excitation fiber 25 may be prepared as a general single mode fiber or multimode fiber in which both the core and the clad are made of glass.

  In addition, a bridge fiber is prepared. In preparing the bridge fiber 50, an optical fiber having the same outer diameter as that of the capillary 40 is drawn while being heated and cut at an appropriate portion. In this way, a bridge fiber 50 having an outer diameter on one side that is the same as that of the capillary 40 and an outer diameter on the other side that is the same as that of the clad 37 of the amplification optical fiber 30 is obtained.

<Insertion process P2>
Next, the end of the seed optical fiber 15 is inserted into the through hole 41 of the capillary 40, and the end of each excitation fiber 25 is inserted into the through hole 42 of the capillary 40. Thus, as shown in FIG. 7, the seed optical fiber 15 and the respective excitation fibers 25 are inserted into the respective through holes 41 and 42 of the capillary 40.

<Integration process P3>
Next, the seed optical fibers 15 and the capillaries 40 in which the respective excitation fibers 25 are inserted into the through holes 41 and 42 are heated, so that the seed optical fibers 15 and the respective excitation fibers 25 and the capillaries 40 are integrated. . In this heating, laser light having a specific wavelength that passes through the glass constituting the capillary 40 and is absorbed by a specific element added to the capillary 40 is used. When samarium is added as a specific element as in the present embodiment, laser light having a wavelength of 1064 nm (for example, Nd: YAG laser) is used as described above. FIG. 8 is a diagram showing the state of this process. As shown in FIG. 8, the laser light is irradiated from the side surface direction of the capillary 40. Then, a specific element added to the capillary absorbs the laser beam and generates heat. Since this specific element is added to the area AR _i within a predetermined range from the center of the capillary as described above, heat is generated from the center side of the capillary 40, and this heat is transferred to the outer peripheral side of the capillary 40. Conduct. In addition, as shown in FIG. 8, it is preferable to irradiate a laser beam from several different directions. By irradiating the laser beam in this way, variation in the amount of heat generated in the area AR _i can be further suppressed.

Thus, as shown in FIGS. 3 and 4, the seed optical fiber 15 and the excitation fiber 25 and the capillary 40 are integrated.
<Connection process P4>
Next, the capillary 40 integrated with the seed optical fiber 15 and the excitation fiber 25 is connected to the bridge fiber 50. In this connection, the end face 51 on the side having the same outer diameter as the outer diameter of the capillary 40 in the bridge fiber 50 and the end face 44 on the side where the seed optical fiber 15 and the excitation fiber 25 are not led out in the capillary 40 are opposed to each other. The core 16 of the seed optical fiber 15 and the core 56 of the bridge fiber 50 are connected so as to coincide with each other. The capillary 40 and the bridge fiber 50 may be connected by melting the end faces of the capillary 40 and the bridge fiber 50 using an oxyhydrogen burner, a Co ₂ laser, or the like.

  In this way, the combiner 3 shown in FIG. 3 is obtained.

  The amplification optical fiber 30 is connected to the end surface of the bridge fiber 50 of the combiner 3 opposite to the capillary 40 side. This connection may be performed in the same manner as the connection between the capillary 40 and the bridge fiber 50.

  As described above, the capillary 40 and the seed optical fiber 15 are irradiated by irradiating laser light of a specific wavelength with the optical fiber such as the seed optical fiber 15 and the excitation fiber 25 inserted into the capillary 40 of the present invention. And an optical fiber such as the excitation fiber 25 can be integrated. At this time, the capillary 40 generates heat on the center side as described above, and this heat is conducted from the center side toward the outer peripheral side. Therefore, the temperature difference between the side irradiated with the laser beam in the capillary 40 and the side opposite to the side irradiated with the laser beam can be suppressed, and the capillary can be heated as a whole. For this reason, it is possible to prevent a part of the optical fibers inserted into the through holes 41 and 42 of the capillary 40 from being excessively heated and distorting the outer peripheral surface of the optical fiber. For this reason, the combiner 3 which can reduce the loss of light by using such a capillary 40 is realizable.

  As described above, the combiner 3 of the present embodiment prevents the outer peripheral surfaces of the seed optical fiber 15 and the pump fiber 25 from being distorted, and thus suppresses the loss of light propagating through the seed optical fiber 15 and the pump fiber 25. Furthermore, in the optical fiber amplifier 2 and the fiber laser device 1 using the combiner 3, loss of pumping light and seed light is suppressed, so that excellent amplification efficiency can be obtained.

Further, in the capillary 40 of the present embodiment, since a specific element is not added to the area AR _o in the outer peripheral side of the area AR _i within the predetermined range, the laser light is emitted on the outer peripheral side of the capillary 40. It is possible to prevent the amount of heat generated at the center of the capillary 40 from being reduced.

(Second Embodiment)
Next, a second embodiment of the present invention will be described in detail with reference to FIG. In addition, about the component which is the same as that of 1st Embodiment, or equivalent, except the case where it demonstrates especially, the same referential mark is attached | subjected and the overlapping description is abbreviate | omitted. FIG. 9 is a view showing a state of the capillary 40a used in the combiner of the present embodiment. Specifically, FIG. 9A is a view showing a state of a cross-sectional structure perpendicular to the longitudinal direction of the capillary 40a. FIG. 9B is a diagram showing a state of concentration distribution of a specific element added to the capillary 40a.

The capillary 40a of this embodiment has the same shape as the capillary 40 of the first embodiment, and is made of glass in the same manner as the capillary 40 of the first embodiment. However, in the capillary 40a of the present embodiment, the concentration of the specific element added to the area AR _i within a predetermined range from the center is gradually increased stepwise from the outer periphery side to the center side of the capillary 40. This is different from the capillary 40 of the first embodiment. For ease of understanding, FIG. 9B shows a specific limit concentration distribution on the assumption that the through hole 42 is not formed, as in FIG. 5B.

Such a capillary 40a is manufactured as follows. First, in the same manner as the production of the capillary in the first embodiment, a first glass tube that is an area AR _o on the outer peripheral side of the area AR _i is prepared. A specific element is not added to the first glass tube. Next, a second glass tube having an outer diameter slightly smaller than the inner diameter of the first glass tube is inserted into the through hole of the first glass tube. A specific element is slightly added to the glass constituting the second glass tube. Next, a third glass tube having an outer diameter slightly smaller than the inner diameter of the second glass tube is inserted into the through hole of the second glass tube. A specific element is added to the glass constituting the third glass tube at a higher concentration than the second glass tube. In this way, glass tubes are inserted one after the other so that the concentration of a specific element is increased in the inner glass tube. Finally, a glass rod is inserted into the portion that becomes the through hole 41. Next, the glass body in which the glass rod is inserted in the center and the glass tube is inserted several times is heated and collapsed to be integrated. Next, a through hole corresponding to the through hole 41 is formed at the radial center of the integrated glass body, and a plurality of through holes are formed so as to correspond to the through hole 42 so as to surround the through hole. To do. This through hole may be formed by a method similar to the method of forming the through hole corresponding to the through hole 42 in the first embodiment. In this way, a base material that becomes the capillary 40a is obtained. In the base material of the capillary 40a, a specific element is added to a region within a predetermined range from the center, and the concentration of the specific element is gradually increased stepwise from the outer peripheral side toward the center side. When fluorine is added to the glass constituting the capillary 40a, fluorine is added to the entire glass constituting the base material that becomes the capillary 40a.

  Next, as in the first embodiment, the base material is drawn by heating while applying a predetermined pressure in each through hole of the base material. Then, the drawn glass body is cut into a predetermined length to obtain the capillary 40a.

  And the combiner using this capillary 40a should just manufacture similarly to 1st Embodiment except using the capillary 40a instead of the capillary 40 of 1st Embodiment. Therefore, the combiner using the capillary 40a of this embodiment has a configuration in which the capillary 40a of this embodiment is used instead of the capillary 40 of the first embodiment.

In the capillary 40a of the present embodiment, the concentration of the specific element is gradually increased stepwise from the outer peripheral side toward the center side in the area AR _i , so that the laser beam is absorbed closer to the center side of the capillary 40a. Increases efficiency. Therefore, in the integration step, when laser light is irradiated from the side surface side of the capillary 40a, the laser light is absorbed by a specific element until the laser light reaches the center of the capillary 40, and the intensity of the laser light is weakened. Even if this occurs, heat can be generated on the center side of the capillary 40a. Therefore, it is possible to balance the heat generation appropriately on the relatively outer peripheral side and the central side in the predetermined range AR _i in which the specific element that absorbs the laser beam is added. Therefore, a combiner that can further reduce the loss of light can be realized.

(Third embodiment)
Next, a third embodiment of the present invention will be described in detail with reference to FIG. In addition, about the component which is the same as that of 1st Embodiment, or equivalent, except the case where it demonstrates especially, the same referential mark is attached | subjected and the overlapping description is abbreviate | omitted. FIG. 10 is a diagram showing a state of the capillary 40b used in the combiner of the present embodiment. Specifically, FIG. 10A is a diagram showing a state of a cross-sectional structure perpendicular to the longitudinal direction of the capillary 40b. FIG. 10B is a diagram showing a state of concentration distribution of a specific element added to the capillary 40b.

  As shown in FIG. 10, the capillary 40b of this embodiment has a plurality of through holes 42a so as to surround a through hole 41 provided in the center, and further surrounds the through hole 41 and each through hole 42a. Thus, a plurality of through holes 42b are formed on the outer peripheral side of the through hole 42a.

Further, in the present embodiment, the boundary between the area AR _{i in a} predetermined range from the center and the area AR _{o in the} outer peripheral side of the predetermined range is defined by the plurality of through holes 42a and the plurality of through holes 42b. It is between. The capillary 40b of the present embodiment is made of glass in the same manner as the capillary 40 of the first embodiment, and a specific element is uniformly added to the area AR _i as in the first embodiment. However, the region AR _o is added with a second specific element that is different from the wavelength of the laser beam having a specific wavelength and absorbs the second laser beam having a wavelength that passes through the glass constituting the capillary 40b. ing. This second specific element is an element different from the first specific element. For example, as in the first embodiment, when the specific element is samarium, the second specific element is, for example, thulium (Tm). Samarium has a high absorptance for laser light with a wavelength of 1064 nm, but a low absorptance for laser light with a wavelength of 1650 nm. On the other hand, thulium has a high absorptance for laser light with a wavelength of 1650 nm, but a low absorptance for laser light with a wavelength of 1064 nm. In this case, when the capillary is irradiated with laser light having a wavelength of 1064 nm, the center side of the capillary is heated as in the first embodiment. Furthermore, if the laser beam having a wavelength of 1650 nm is irradiated, the outer peripheral side of the capillary can be heated in a complementary manner.

  Note that FIG. 10B shows a state in which the concentration of the second specific element is added lower than the concentration of the specific element, but the concentration of the second specific element is The concentration may be higher than the element concentration or may be equivalent.

  In order to prepare such a capillary 40b, thulium may be added to the first glass tube in the preparation step of the first embodiment.

  And the combiner using this capillary 40b should just manufacture similarly to 1st Embodiment except using the capillary 40b instead of the capillary 40 of 1st Embodiment. Therefore, the combiner using the capillary 40b of this embodiment has a configuration in which the capillary 40b of this embodiment is used instead of the capillary 40 of the first embodiment.

  In the capillary 40b having such a configuration, the entire capillary can be further heated by heating the outer peripheral side with the second laser beam.

  Although the present invention has been described above by taking the first to third embodiments as examples, the present invention is not limited to these.

  For example, in the second embodiment, the concentration of the specific element is gradually increased stepwise from the outer peripheral side to the center side, but may be gradually increased with a gentle gradient instead of the step shape.

  In the third embodiment, the concentration of the specific element or the second specific element may be gradually increased from the outer peripheral side to the center side. In this case, it may be gradually increased stepwise, or may be gradually increased with a gentle gradient.

  Further, the specific element and the second specific element are not limited to samarium and thulium, and may be other elements. For example, neodymium (Nd) can absorb laser light having a wavelength of 1550 nm and pass through glass. Similarly, if it is protheodymium (Pr), it can absorb laser light having a wavelength of 1450 nm and transmit through the glass. In addition to the above, examples of the element that absorbs laser light having a wavelength that passes through the glass include ytterbium (Yb), dysprosium (Dy), and erbium (Er).

In the first and second embodiments, in a region AR _o outside the predetermined range from the center, a specific element may be added at a lower concentration than the region AR _i within the predetermined range.

  In the combiner of the above embodiment, the bridge fiber 50 as another optical fiber different from the seed optical fiber 15 and the excitation fiber 25 is connected to the capillary 40. However, the present invention is not limited to this, and other optical fibers are used. As an amplification optical fiber, the capillary 40 and the amplification optical fiber 30 may be directly connected. In this case, the outer diameter of the clad 37 of the amplification optical fiber 30 and the outer diameter of the capillary 40 are the same. Thus, the optical fiber to which the capillary 40 is connected is not particularly limited.

  Furthermore, the optical fibers inserted into the respective through holes 41 and 42 of the capillary 40 are not limited to the seed optical fiber 15 and the excitation fiber 25, and other optical fibers may be inserted.

  As described above, according to the present invention, a capillary capable of realizing a combiner capable of reducing light loss, a combiner using the capillary, and a method for manufacturing the combiner are provided.

DESCRIPTION OF SYMBOLS 1 ... Fiber laser apparatus 2 ... Optical fiber amplifier 3 ... Combiner 10 ... Seed light source 15 ... Seed optical fiber 16 ... Core 17 ... Cladding 20 ... Excitation light source 25. ..Excitation fiber 26 ... Core 27 ... Clad 30 ... Amplification optical fiber 36 ... Core 37 ... Clad 38 ... Resin clad 40, 40a, 40b ... Capillary 41, 42 , 42a, 42b ... through hole 50 ... bridge fiber 56 ... core 58 ... cladding P1 ... preparation process P2 ... insertion process P3 ... integration process P4 ... connection process

Claims (9)

A plurality of through-holes are formed along the longitudinal direction, and a specific element that absorbs laser light having a specific wavelength that passes through the glass within a predetermined range from the center in a plane perpendicular to the longitudinal direction is the predetermined element. A capillary characterized by being added at a concentration higher than outside the range. 2. The capillary according to claim 1, wherein the additive concentration of the element is gradually increased from an outer peripheral side to the center side in a plane perpendicular to the longitudinal direction.   3. The capillary according to claim 1, wherein the specific element is not added to a range on the outer peripheral side of the predetermined range.   The second specific element that absorbs a second laser beam having a wavelength different from that of the laser beam having the specific wavelength is added to a range outside the predetermined range. 2. The capillary according to 1. A plurality of through-holes are formed along the longitudinal direction, and a specific element that absorbs laser light having a specific wavelength that passes through the glass within a predetermined range from the center in a plane perpendicular to the longitudinal direction is the predetermined element. A capillary added at a higher concentration than out of range; and
A plurality of optical fibers inserted into the respective through holes of the capillaries and integrated with the capillaries;
Other optical fibers to which end faces of the capillary and the plurality of optical fibers are connected;
A combiner comprising: A plurality of through-holes are formed along the longitudinal direction, and a specific element that absorbs laser light having a specific wavelength that passes through the glass within a predetermined range from the center in a plane perpendicular to the longitudinal direction is the predetermined element. An insertion step of inserting an optical fiber into each through hole of the capillary added at a concentration higher than outside the range;
An integration step of irradiating the laser beam of the specific wavelength from the side surface direction of the capillary to heat the capillary and integrate the optical fiber and the capillary;
A connection step of connecting the end faces of the capillaries and the respective optical fibers to other optical fibers;
A method for manufacturing a combiner comprising:   The method for manufacturing a combiner according to claim 6, wherein the laser beam having the specific wavelength is irradiated from a plurality of different directions. A second specific element that absorbs a second laser beam having a wavelength different from the laser beam having the specific wavelength is added to the outer peripheral side of the predetermined range in the capillary.
The method for manufacturing a combiner according to claim 6 or 7, wherein in the integration step, the capillary is further heated by irradiating the second laser light from a side surface direction of the capillary.   The method for manufacturing a combiner according to claim 8, wherein the second laser light is irradiated from a plurality of different directions.

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