JP2015014800A - Optical device and fiber laser equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical device that prevents deterioration of resin covering an outer shell removal section at a fusing and bonding point of two optical fibers.SOLUTION: A first medium 130, having a refractive index lower than those of outermost shell structures of an outer shell removal section 110A of an optical fiber 110 and an outer shell removal section 120A of an optical fiber 120, surrounds a whole side of the outer shell removal section 110A. A second medium 140, having a refractive index higher than that of the outermost shell structure of the outer shell removal section 120A, surrounds at least a portion of a side of the outer shell removal section 120A. Then, a diameter of an outer shell removal section 120B is made larger than a diameter of the outer shell removal section 110A.

Description

  The present invention relates to an optical device including two optical fibers fused to each other, and a fiber laser apparatus including the optical device.

  In fields such as laser processing and laser communication, fiber laser devices and fiber amplifier devices are widely used. Such an apparatus is usually an amplification fiber which is a double clad fiber in which an activation element (for example, rare earth ions such as ytterbium) is added to a core, and a single clad fiber (single mode fiber) or a double clad fiber. And a transmission fiber.

  Excitation light is input to the inner cladding of the amplification fiber via a combiner inserted in the amplification fiber. This excitation light is used to transition the active element added to the core of the amplification fiber to the inverted distribution state. The fusion point between the amplifying fiber and the transmission fiber is usually covered with a high refractive index resin, and the residual excitation light remaining without being absorbed by the active element is absorbed by the high refractive index resin.

  However, when the output of a semiconductor laser used as an excitation light source is increased in order to meet the demand for higher output, high-energy residual excitation light enters the high refractive resin. In addition, high energy core light that has entered the cladding of the transmission fiber from the core of the amplification fiber at the fusion point also enters the high refractive index resin. When the high refractive index resin is a transparent resin, most of the light leakage incident on the high refractive index resin passes through the high refractive index resin. However, part of the light leakage incident on the high refractive index resin is absorbed by the high refractive index resin, causing the high refractive index resin to generate heat. For this reason, deterioration of high refractive index resin is accelerated | stimulated, As a result, the problem that the reliability of an apparatus falls arises.

  As a technique for solving such a problem, for example, there is an optical fiber protector described in Patent Document 1. Patent Document 1 discloses an optical fiber protector for protecting a fusion splicing portion between double clad fibers (or a splicing splicing portion between a double clad fiber and a single clad fiber). The structure which covers with transparent resin and fixes the said transparent resin in the accommodation groove | channel formed in the heat sink is disclosed.

JP 2007-271786 A (released on October 18, 2007)

  However, even if the technique described in Patent Document 1 is used, light leaked from the side surface of the optical fiber in the vicinity of the fusion point remains incident on the transparent resin, and part of the light leakage is absorbed by the transparent resin. The transparent resin is heated. In particular, light having a high energy density is incident on a portion close to the optical fiber of the transparent resin. For this reason, even if the technique described in Patent Document 1 is used, deterioration of the portion adjacent to the optical fiber made of transparent resin is inevitable. The problem becomes more serious as the diameter of the optical fiber near the fusion point decreases. This is because as the diameter of the optical fiber in the vicinity of the fusion point becomes smaller, the energy density of light leakage incident on the portion near the optical fiber made of transparent resin becomes higher.

  The present invention has been made in view of the above problems, and an object of the present invention is to realize an optical device in which deterioration of a resin covering the fusion point of two optical fibers is less likely to occur than in the past.

  The optical device according to the present invention includes a first optical fiber from which the outer shell structure is removed in the first section including the end face, and a second optical fiber from which the outer shell structure is removed in the second section including the end face. A second optical fiber whose end face is fused to the end face of the first optical fiber, an outermost shell structure in the first section of the first optical fiber, and the first optical fiber. A first medium having a refractive index lower than that of the outermost shell structure in the second section of the second optical fiber, and surrounding the side surface of the first optical fiber in the entire first section. And a second medium having a refractive index higher than that of the outermost shell structure in the second section of the second optical fiber, wherein the second optical fiber is at least partially in the second section. A second medium surrounding the side surface, and the first medium The outermost shell structure in the first section of the fiber and the outermost shell structure in the second section of the second optical fiber have intersections at the end face, and the first medium and the The diameter of the second optical fiber at the boundary with the second medium is larger than the diameter of the first optical fiber.

  The first optical fiber is surrounded by a first medium having a refractive index lower than that of the outermost shell structure in the entire outer shell removing section (“first section” in the claims), and The outermost shell structure in the outer shell removal section of the first optical fiber has a second optical fiber outer shell removal section (“second section” in the claims) at the end surface welded to the second optical fiber. ) With the outermost shell structure. For this reason, the light (residual pumping light, etc.) propagating through the outermost shell structure in the outer shell removal section of the first optical fiber hardly leaks into the first medium from the side surface of the first optical fiber. The light enters the outermost shell structure in the outer shell removal section of the second optical fiber from the end face of the first optical fiber. The second optical fiber is surrounded by a second medium having a refractive index higher than that of the outermost shell structure in at least a part of the outer shell removal section. For this reason, after propagating through the outermost shell structure in the outer shell removal section of the first optical fiber, the light incident on the outermost shell structure in the outer shell removal section of the second optical fiber from the end face of the first optical fiber Enters the second medium from the side surface of the second optical fiber.

  Therefore, according to the above configuration, light propagating through the outermost shell structure in the outer shell removal section of the first optical fiber is removed without causing almost any deterioration of the first medium due to light leakage (second (Can be incident on the second medium from the side surface of the optical fiber).

  In addition, after entering the outermost shell structure in the outer shell removal section of the second optical fiber from the end face of the first optical fiber, the energy of light leakage entering the second medium from the side surface of the second optical fiber is: It becomes the largest at the boundary between the first medium and the second medium, and gradually decreases as the distance from the boundary increases. According to the above configuration, since the diameter of the second optical fiber at the boundary is larger than the diameter of the first optical fiber, the light enters the second medium from the side surface of the second optical fiber in the vicinity of the boundary. The energy density of light leakage is determined as the light leakage incident on the first medium from the side of the first optical fiber (when the refractive index of the first medium is higher than the refractive index of the outermost shell structure of the first optical fiber). It can be made smaller than the energy density. Therefore, deterioration of the second medium due to light leakage can be suppressed.

  In the optical device according to the present invention, the first optical fiber is a double clad fiber, and the outermost shell structure in the first section of the first optical fiber is an inner clad of the double clad fiber. Preferably, the outermost shell structure in the second section of the second optical fiber has an intersection with the inner clad of the double clad fiber at the end face.

  According to the above configuration, the light propagating through the inner cladding of the first optical fiber hardly leaks from the side surface of the first optical fiber to the first medium, and is second from the end surface of the first optical fiber. Is incident on the optical fiber. Then, the light incident on the outermost shell structure in the outer shell removal section of the second optical fiber from the end face of the first optical fiber has a large diameter in the vicinity of the boundary between the first medium and the second medium. The light enters the second medium from the side surface of the optical fiber. Therefore, the deterioration of the first medium that can be caused by light leakage is avoided, and the deterioration of the second medium that can be caused by light leakage is suppressed.

  In the optical device according to the present invention, it is preferable that a refractive index of the first medium is not more than a refractive index of the outer clad of the double clad fiber.

  According to the above configuration, the light confined in the inner clad of the first optical fiber by the action of the outer clad outside the outer shell removal section is transmitted to the first optical fiber by the action of the first medium in the outer shell removal section. Trapped in the inner cladding. For this reason, the light propagating through the inner cladding of the first optical fiber does not leak into the first medium from the side surface of the first optical fiber, but from the end face of the first optical fiber to the second optical fiber. Incident. Therefore, the deterioration of the first medium that may occur due to light leakage is more reliably avoided.

  In the optical device according to the present invention, the first optical fiber is a triple clad fiber, and the outermost shell structure in the first section of the first optical fiber is a second clad of the triple clad fiber. The outermost shell structure in the second section of the second optical fiber has an intersection with the second cladding of the triple-clad fiber at the end face, or the first of the triple-clad fiber. It is preferable to have an intersection with the clad and the second clad.

  According to said structure, the light which propagates the 2nd clad of the 1st optical fiber, or the light which propagates the 1st clad and the 2nd clad of the 1st optical fiber is almost the side surface of the 1st optical fiber. From the end face of the first optical fiber to the second optical fiber without leaking into the first medium. Then, the light incident on the outermost shell structure in the outer shell removal section of the second optical fiber from the end face of the first optical fiber has a large diameter in the vicinity of the boundary between the first medium and the second medium. The light enters the second medium from the side surface of the optical fiber. Therefore, the deterioration of the first medium that can be caused by light leakage is avoided, and the deterioration of the second medium that can be caused by light leakage is suppressed.

  In the optical device according to the present invention, it is preferable that a refractive index of the first medium is equal to or lower than a refractive index of the third clad of the triple clad fiber.

  According to the above configuration, the light confined in the second cladding of the first optical fiber by the action of the third cladding outside the outer shell removal section is the first light by the action of the first medium in the outer shell removal section. It is confined to the second cladding of the optical fiber. Light propagating through the second cladding of the first optical fiber enters the second optical fiber from the end surface of the first optical fiber without leaking into the first medium from the side surface of the first optical fiber. . Therefore, the deterioration of the first medium that may occur due to light leakage is more reliably avoided.

  In the optical device according to the present invention, it is preferable that the section of the second optical fiber is longer than the section of the first optical fiber.

  In the optical device according to the present invention, the length of the second medium measured along the central axis of the first optical fiber and the second optical fiber is measured along the central axis. It is preferably longer than the length of the first medium.

  According to the above configuration, the length of the portion surrounded by the second medium is sufficiently increased in the section where the outer shell of the second optical fiber is removed without causing an increase in the size of the optical device. be able to. Therefore, unnecessary light such as residual excitation light can be sufficiently removed.

  In the optical device according to the present invention, the section of the second optical fiber may have a cylindrical shape with a constant diameter, or is separated from a fusion point with the first optical fiber. The taper may have a tapered shape with a diameter that decreases according to the diameter, or may have a tapered shape with a diameter that increases as the distance from the fusion point with the first optical fiber increases.

  In any case, deterioration of the first medium that can be caused by light leakage is avoided, and deterioration of the second medium that can be caused by light leakage is suppressed. In particular, when the second optical fiber has a tapered shape whose diameter decreases as the distance from the fusion point with the first optical fiber increases, the second optical fiber leaks from the side surface of each part of the second optical fiber. There is a further effect that the energy density of light can be made uniform. In addition, when the second optical fiber has a tapered shape whose diameter increases as the distance from the fusion point with the first optical fiber increases, the relationship between the first optical fiber and the second optical fiber There is a further effect that welding is facilitated.

  The optical device according to the present invention further includes a heat radiator having a groove formed therein, and the section of the first optical fiber and the section of the second optical fiber are accommodated in the groove of the heat radiator. The first medium and the second medium are preferably resin filling the groove.

  According to said structure, the said optical device can be manufactured easily. Moreover, the leak light leaked into the second medium from the side surface of the second optical fiber can be efficiently converted into heat by the radiator.

  A fiber laser apparatus provided with the optical device is also included in the scope of the present invention.

  According to the present invention, deterioration of the first medium that can be caused by light leakage is avoided, and deterioration of the second medium that can be caused by light leakage is suppressed.

It is a trihedral view of an optical device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the optical device shown in FIG. 1, showing a first specific example of a structure in the vicinity of the fusion point. It is sectional drawing of the optical device shown in FIG. 1, Comprising: It is sectional drawing which shows the effect of the structure shown in FIG. FIG. 2 is a cross-sectional view of the optical device shown in FIG. 1, showing a second specific example of the structure near the fusion point. FIG. 5 is a cross-sectional view of the optical device shown in FIG. 1, showing a third specific example of the structure near the fusion point. FIG. 6 is a cross-sectional view of the optical device shown in FIG. 1, showing a fourth specific example of the structure near the fusion point. FIG. 10 is a cross-sectional view of the optical device shown in FIG. 1, showing a fifth specific example of the structure near the fusion point. It is a figure which shows typically the structure of the fiber laser apparatus which is the 1st application example of the optical device shown in FIG. It is a figure which shows typically the structure of the fiber laser apparatus which is the 2nd application example of the optical device shown in FIG.

  An optical device according to an embodiment of the present invention will be described below with reference to the drawings.

[Schematic configuration of optical device]
First, a schematic configuration of the optical device 100 according to the present embodiment will be described with reference to FIG. FIG. 1 is a three-view diagram (upper left: plan view, lower left: side view, upper right: front view) showing the configuration of the optical device 100.

  As shown in FIG. 1, the optical device 100 includes a first optical fiber 110, a second optical fiber 120, a first medium 130, a second medium 140, and a heat radiator 150.

  The first optical fiber 110 is an optical fiber from which an outer shell structure such as a coating is removed in a section 110A including one end face. The section 110A from which the outer shell structure is removed in the first optical fiber 110 is hereinafter referred to as an outer shell removal section 110A. The specific structure of the first optical fiber 110 will be described later with reference to another drawing.

  The second optical fiber 120 is an optical fiber from which an outer shell structure such as a coating is removed in the section 120A including one end face. The section 120A from which the outer shell structure is removed in the second optical fiber 120 is hereinafter referred to as an outer shell removal section 120A. The specific structure of the second optical fiber 120 will be described later with reference to another drawing.

  The end face of the first optical fiber 110 (the end face included in the outer shell removal section 110A) and the end face of the second optical fiber 120 (the end face included in the outer shell removal section 120A) are the center of the first optical fiber 110. Fusion is performed such that the axis coincides with the central axis of the second optical fiber 120. The diameter (outer diameter) of the second optical fiber 120 in the outer shell removal section 120A is larger than the diameter (outer diameter) of the first optical fiber 110 in the outer shell removal section 110A. The outermost shell structure in the shell removal section 120A intersects with the outermost shell structure in the outer shell removal section 110A of the first optical fiber 110 at the fusion point P.

  The heat radiator 150 is a rectangular parallelepiped member made of a material having high thermal conductivity such as metal, and has a function of converting light leaked from the side surface of the second optical fiber 120 into heat, as will be described later. A groove 152 extending from one short side to the other short side is formed on the upper surface of the heat radiating body 150 along its long side.

  The first optical fiber 110 and the second optical fiber 120 are accommodated in a groove 152 formed in the heat radiating body 150, and fixed to the heat radiating body 150 by an adhesive 162 and an adhesive 164 filled in both ends of the groove 152. Is done. The place where the adhesive 162 and the adhesive 164 are provided is outside the outer shell removing section 110A and the outer shell removing section 120B, and the entire outer shell removing section 110A and the outer shell removing section 120B are the adhesive 162 and the adhesive 164. Between.

  Further, an intermediate portion (a portion between the adhesive 162 and the adhesive 164) of the groove 152 formed in the radiator 150 is filled with the first medium 130 and the second medium 140. That is, the section including the fusion point P of the first optical fiber 110 and the second optical fiber 120 is surrounded by the first medium 130 and the second medium 140.

  The first medium 130 has a lower refractive index than the outermost shell structure in the outer shell removal section 110A of the first optical fiber 110 and the outermost shell structure in the outer shell removal section 120A of the second optical fiber 120. It is a medium and surrounds the entire side surface of the outer shell removal section 110A of the first optical fiber 110. The first medium 130 may be resin, air, or other medium.

  The second medium 140 is a medium having a refractive index higher than that of the outermost shell structure in the outer shell removal section 120A of the second optical fiber 120, and at least on the side surface of the outer shell removal section 120A of the second optical fiber 120. Enclose part. The second medium 140 may be a resin or other medium.

  In the present embodiment, the boundary B between the first medium 130 and the second medium 140 is second than the position of the fusion point P between the first optical fiber 110 and the second optical fiber 120. It is arranged on the optical fiber 120 side. That is, the first medium 130 surrounds not only the entire side surface of the outer shell removal section 110A of the first optical fiber 110 but also the side surface of the tip portion of the outer shell removal section 120A of the second optical fiber 120. However, the present invention is not limited to this. That is, the boundary B between the first medium 130 and the second medium 140 may be disposed so as to pass through the fusion point P between the first optical fiber 110 and the second optical fiber 120. In this case, the entire side surface of the outer shell removal section 120 </ b> A of the second optical fiber 120 is surrounded by the second medium 140.

  In the optical device 100, energy leaks from the side surface of the small-diameter first optical fiber 110 even though light leakage having a low energy density may enter the second medium 140 from the side surface of the large-diameter second optical fiber 120. High density light leakage hardly enters the first medium 130. This is because the side surface of the first optical fiber 110 is surrounded by the first medium 130 having a lower refractive index than the outermost shell structure in the entire outer shell removal section 110A, and the side surface of the second optical fiber 120 is This is because at least a part of the outer shell removal section 120A is surrounded by the first medium 130 having a refractive index higher than that of the outermost shell structure. Therefore, the deterioration of the first medium 130 that can be caused by light leakage is avoided, and the deterioration of the second medium 140 that can be caused by light leakage is suppressed. Such an effect can be obtained regardless of the structure of the first optical fiber 110 and the second optical fiber 120. That is, even if the first optical fiber 110 is a single clad fiber, a double clad fiber, or a triple clad fiber, the second optical fiber 120 is a single clad fiber, a double clad fiber, or a triple clad fiber. In any case, such an effect is not impaired.

  In the optical device 100, as described above, light leaks from a portion surrounded by the second medium 140 in the outer shell removal section 120A of the second optical fiber 120. Therefore, in order to sufficiently remove unnecessary light (for example, clad light propagating through the clad of the first optical fiber 110) by the optical device 100, the outer shell removing section 120A of the second optical fiber 120 is used in the first shell removal section 120A. It is preferable that the length of the portion surrounded by the second medium 140 is sufficiently long. In the configuration shown in FIG. 1, (1) the length of the outer shell removal section 120A of the second optical fiber 120 measured along the fiber axis is the outer shell of the first optical fiber 110 measured along the fiber axis. It is longer than the length of the removal section 110A, and (2) the length of the second medium 140 measured along the fiber axis is longer than the length of the first medium 130 measured along the fiber axis. This is why.

[First Example]
The optical device 100 is characterized by a structure near the fusion point. Hereinafter, a first specific example of the structure in the vicinity of the fusion point of the optical device 100 will be described with reference to FIG. FIG. 2 is a cross-sectional view schematically showing the structure near the fusion point of the optical device 100 according to this example.

  In this specific example, a double clad fiber is used as the first optical fiber 110. That is, the first optical fiber 110 includes a core 112, an inner clad 114 surrounding the core 112, an outer clad 116 surrounding the inner clad 114, and a coating 118 surrounding the outer clad.

  For example, silica glass or the like is used as the material of the core 112 and the inner cladding 114. In addition, as the material of the outer clad 116 and the coating 118, for example, a resin or the like is used. In the outer shell removal section 110A, the outer clad 116 and the coating 118 are removed, and the inner clad 114 has an outermost shell structure.

  In the first optical fiber 110, the refractive index of the inner cladding 114 is set lower than the refractive index of the core 112. This is to confine light in the core 112. The light propagating through the first optical fiber 110 while being confined in the core 112 is hereinafter referred to as “core light”. Further, in the first optical fiber 110, the refractive index of the outer cladding 116 is set lower than the refractive index of the inner cladding 114. This is to confine light in the inner cladding 114. Hereinafter, the light propagating through the first optical fiber 110 while being confined in the inner cladding 114 will be referred to as “cladding light”.

  In this specific example, a single clad fiber is used as the second optical fiber 120. That is, the second optical fiber 120 includes a core 122, a clad 124 that surrounds the core 112, and a coating 126 that surrounds the clad 124. The diameter of the core 122 of the second optical fiber 120 is the same as the diameter of the core 112 of the core 112 of the first optical fiber 110, and the diameter (outer diameter) D2 of the clad 124 of the second optical fiber 120 is The diameter (outer diameter) D1 of the inner cladding 114 of one optical fiber 110 is larger.

  For example, glass or the like is used as the material of the core 122 and the clad 124. Further, as the material of the covering 126, for example, a resin or the like is used. In the outer shell removal section 120A, the coating 126 is removed, and the clad 124 has an outermost shell structure.

  In the second optical fiber 120, the refractive index of the clad 124 is set lower than the refractive index of the core 122. This is to confine light in the core 122. Hereinafter, the light propagating through the second optical fiber 120 while being confined in the core 122 is referred to as “core light”.

  The entire outer side of the outer shell removal section 110A of the first optical fiber 110 is surrounded by the first medium 130. The first medium 130 is a medium having a lower refractive index than the inner clad 114 that is the outermost shell structure of the first optical fiber 110 in the outer shell removal section 110A. For this reason, leakage of light from the first optical fiber 110 to the first medium 130 hardly occurs.

  In particular, in this specific example, the refractive index of the first medium 130 is set to be equal to or lower than the refractive index of the outer cladding 116 of the first optical fiber 110. For this reason, the light confined in the inner cladding 114 by the action of the outer cladding 116 outside the outer shell removal section 110A is confined in the inner cladding 114 by the action of the first medium 130 in the outer shell removal section 110A. Therefore, the clad light propagating through the first optical fiber 110 does not leak into the first medium 130 from the side surface of the first optical fiber 110, and the second optical fiber from the end surface of the first optical fiber 110. The light enters the clad 124 of 120.

  In the outer shell removal section 120A of the second optical fiber 120, the side surface of the tip portion is surrounded by the first medium 130, and the side surface of the portion other than the tip portion is surrounded by the second medium 140. The first medium 130 is a medium having a lower refractive index than the clad 124 that is the outermost shell structure of the second optical fiber 120 in the outer shell removal section 120A. For this reason, leakage of light from the second optical fiber 120 to the first medium 130 hardly occurs. On the other hand, the second medium 140 is a medium having a higher refractive index than the clad 124 that is the outermost shell structure of the second optical fiber 120 in the outer shell removal section 120A. For this reason, leakage of light from the second optical fiber 120 to the second medium 140 occurs.

  Next, effects obtained in the optical device 100 according to this example will be described with reference to FIG. Here, attention is focused on the core light L1 and the clad light L2 propagating through the first optical fiber 110 toward the second optical fiber 120. The cladding light L2 propagating through the first optical fiber 110 includes residual pumping light (when the first optical fiber 110 is an amplification fiber) and the fusion point P side of the first optical fiber 110. The light incident on the inner cladding 114 of the first optical fiber 110 is assumed on the opposite end face.

  The clad light L2 having propagated through the first optical fiber 110 enters the clad 124 of the second optical fiber 120 without leaking from the side surface of the first optical fiber 110. This is because the entire side surface of the first optical fiber 110 is surrounded by the first medium in the outer shell removal section 110A, and the inner cladding of the first optical fiber 110 is formed at the end surface constituting the fusion point P. 114 is included in the clad 124 of the second optical fiber 120.

  The clad light L2 incident on the clad 124 of the second optical fiber 120 propagates through the second optical fiber 120 without leaking into the first medium 130, and then the second light fiber 120 passes through the second optical fiber 120 from the side surface. It leaks into the medium 140. This is because the refractive index of the first medium 130 is lower than the refractive index of the clad 124 of the second optical fiber 120, and the refractive index of the second medium 140 is the clad of the second optical fiber 120. This is because the refractive index is higher than 124.

  Further, a part of the core light L <b> 1 propagated through the first optical fiber 110 is incident on the clad 124 of the second optical fiber 120. The core light L1 propagated through the first optical fiber 110 is incident on the clad 124 of the second optical fiber 120 mainly due to an axial misalignment between the first optical fiber 110 and the second optical fiber 120. This is the case. The light L3 incident on the clad 124 of the second optical fiber 120 in this way also propagates through the second optical fiber 120 without leaking into the first medium 130, and then from the side surface of the second optical fiber 120. It leaks into the second medium 140.

  As described above, the core light L1 and the clad light L2 propagated through the first optical fiber 110 are second from the side surface of the second optical fiber 120 except for the light incident on the core 122 of the second optical fiber 120. Leaks into the medium 140. That is, even if light leakage having a low energy density enters the second medium 140 from the side surface of the second optical fiber 120 having a large diameter, the light leakage having a high energy density from the side surface of the first optical fiber 110 having a small diameter. Does not enter the first medium 130. Therefore, the deterioration of the first medium 130 that can be caused by light leakage is avoided, and the deterioration of the second medium 140 that can be caused by light leakage is suppressed.

[Second specific example]
Next, a second specific example of the structure in the vicinity of the fusion point of the optical device 100 will be described with reference to FIG. FIG. 4 is a cross-sectional view schematically showing the structure near the fusion point of the optical device 100 according to this example.

  The optical device 100 according to this example is different from the optical device 100 according to the first example in the following points. That is, in the first specific example, the outer shell removal section 120A of the second optical fiber 120 has a cylindrical shape with a constant diameter, whereas in this specific example, the second optical fiber 120 The outer shell removing section 120A has a tapered shape in which the diameter gradually decreases as the distance from the fusion point P increases. In other respects, the optical device 100 according to this example is configured in the same manner as the optical device 100 according to the first example.

  Most of the light incident on the clad 124 of the second optical fiber 120 from the first optical fiber 110 propagates through the second optical fiber 120 without leaking to the first medium 130, and then the second light. It leaks into the second medium 140 from the side surface of the fiber 120. At this time, when the energy of leakage light leaking from the side surface in each part of the second optical fiber 120 is compared, the energy leaking from the side surface in the part near the boundary B between the first medium 130 and the second medium 140 is calculated. The energy of light leakage leaking from the side surface becomes smaller as the portion becomes farther from the boundary B between the first medium 130 and the second medium 140. In other words, light incident on the clad 124 of the second optical fiber 120 from the first optical fiber 110 is near the boundary B between the first medium 130 and the second medium 140 (second medium). 140 side) leaks intensively.

  Therefore, as shown in FIG. 4, the diameter D2 of the second optical fiber 120 at the boundary B between the first medium 130 and the second medium 140 is larger than the diameter D1 of the first optical fiber 110. Is adopted, the energy density of light leakage incident on the second medium 140 from the side surface of the second optical fiber 120 can be sufficiently reduced. That is, as with the optical device 100 according to the first specific example, it is possible to suppress the deterioration of the second medium 140 that may be caused by light leakage. Further, as shown in FIG. 4, if a configuration in which the diameter of the second optical fiber 120 gradually decreases as the distance from the fusion point P is adopted, light leakage leaking from the side surface at each part of the second optical fiber 120. The energy density of the second medium 140 can be made uniform, and as a result, the deterioration of the second medium 140 that may be caused by light leakage can be more effectively suppressed.

  In this specific example, as shown in FIG. 4, the minimum value of the diameter of the second optical fiber 120 in the outer shell removal section 120A is smaller than the diameter D1 of the first optical fiber 110 in the outer shell removal section 110A. It is getting bigger. For this reason, even when light propagates through the clad 124 of the second optical fiber 120 toward the first optical fiber 110, light leakage with high energy density does not enter the second medium 140.

[Third example]
Next, a third specific example of the structure near the fusion point of the optical device 100 will be described with reference to FIG. FIG. 5 is a cross-sectional view schematically showing the structure near the fusion point of the optical device 100 according to this example.

  The optical device 100 according to this specific example is different from the optical device 100 according to the first specific example in that the diameter of the outer shell removal section 120A of the second optical fiber 120 gradually increases as the distance from the fusion point P increases. It is a point which has a taper shape which becomes large. In other respects, the optical device 100 according to this example is configured in the same manner as the optical device 100 according to the first example.

  Most of the light incident on the clad 124 of the second optical fiber 120 from the first optical fiber 110 propagates through the second optical fiber 120 without leaking to the first medium 130, and then the second light. It leaks into the second medium 140 from the side surface of the fiber 120. At this time, when the energy of leakage light leaking from the side surface in each part of the second optical fiber 120 is compared, the energy leaking from the side surface in the part near the boundary B between the first medium 130 and the second medium 140 is calculated. The energy of light leakage leaking from the side surface becomes smaller as the portion becomes farther from the boundary B between the first medium 130 and the second medium 140. In other words, light incident on the clad 124 of the second optical fiber 120 from the first optical fiber 110 is near the boundary B between the first medium 130 and the second medium 140 (second medium). 140 side) leaks intensively.

  Therefore, as shown in FIG. 5, the diameter D2 of the second optical fiber 120 at the boundary B between the first medium 130 and the second medium 140 is larger than the diameter D1 of the first optical fiber 110. Is adopted, the energy density of light leakage incident on the second medium 140 from the side surface of the second optical fiber 120 can be sufficiently reduced. That is, as with the optical device 100 according to the first specific example, it is possible to suppress the deterioration of the second medium 140 that may be caused by light leakage.

  In this specific example, as shown in FIG. 5, the diameter of the outer shell removal section 110A of the first optical fiber 110 and the diameter of the outer shell removal section 120A of the second optical fiber 120 are fused. A configuration of matching at the point P is adopted. Therefore, there is a secondary effect that the fusion work between the first optical fiber 110 and the second optical fiber 120 is facilitated.

[Fourth example]
Next, a fourth specific example of the structure in the vicinity of the fusion point of the optical device 100 will be described with reference to FIG. FIG. 6 is a cross-sectional view schematically showing the structure near the fusion point of the optical device 100 according to this example.

  In this specific example, a triple clad fiber is used as the first optical fiber 110. That is, the first optical fiber 110 includes a core 111, a first cladding 113 surrounding the core 111, a second cladding 115 surrounding the first cladding 113, and a third cladding 117 surrounding the second cladding 115. In the outer shell removal section 110A, the third cladding 117 is removed, and the second cladding 115 has an outermost shell structure.

  In this specific example, a triple clad fiber is used as the second optical fiber 120. That is, the second optical fiber 120 includes a core 121, a first cladding 123 surrounding the core 121, a second cladding 125 surrounding the first cladding 123, and a third cladding 127 surrounding the second cladding 125. In the outer shell removal section 120A, the third cladding 127 is removed, and the second cladding 125 has an outermost shell structure.

  The outer diameter of the second cladding 123 of the second optical fiber 120, the outer diameter of the first cladding 113 of the first optical fiber 110, the outer diameter of the second cladding 115 of the first optical fiber 110, and the second The following magnitude relationship exists between the outer diameters of the second cladding 125 of the optical fiber 120. For this reason, the second cladding 115 of the first optical fiber 110 intersects only with the second cladding 125 of the second optical fiber 120 at the fusion point P.

The outer diameter of the first cladding 123 of the second optical fiber 120
<Outer diameter of the first cladding 113 of the first optical fiber 110
<Outer diameter of the second cladding 115 of the first optical fiber 110
<Outer Diameter of Second Cladding 125 of Second Optical Fiber 120 In the outer shell removal section 110 </ b> A of the first optical fiber 110, the entire side surface is surrounded by the first medium 130. The first medium 130 is a medium having a refractive index lower than that of the second cladding 115 that is the outermost shell structure of the first optical fiber 110 in the outer shell removal section 110A. For this reason, leakage of light from the first optical fiber 110 to the first medium 130 hardly occurs.

  In particular, in this specific example, the refractive index of the first medium 130 is set to be equal to or lower than the refractive index of the third cladding 117 of the first optical fiber 110. For this reason, the light confined in the second clad 115 by the action of the third clad 117 outside the outer shell removal section 110A is confined in the second clad 115 by the action of the first medium 130 in the outer shell removal section 110A. Therefore, the light that has propagated through the second cladding 115 of the first optical fiber 110 does not leak into the first medium 130 from the side surface of the first optical fiber 110 and does not leak from the end surface of the first optical fiber 110. The light enters the second cladding 125 of the second optical fiber 120.

  In the outer shell removal section 120A of the second optical fiber 120, the side surface of the tip portion is surrounded by the first medium 130, and the side surface of the portion other than the tip portion is surrounded by the second medium 140. The first medium 130 is a medium having a refractive index lower than that of the second cladding 125 that is the outermost shell structure of the second optical fiber 120 in the outer shell removal section 120A. For this reason, leakage of light from the side surface of the second optical fiber 120 to the first medium 130 hardly occurs. On the other hand, the second medium 140 is a medium having a higher refractive index than the second clad 125 that is the outermost shell structure of the second optical fiber 120 in the outer shell removal section 120A. For this reason, leakage of light from the side surface of the second optical fiber 120 to the second medium 140 occurs.

  In the optical device 100 according to this example, the light propagated through the second clad 115 of the first optical fiber 110 is incident on the second clad 125 of the second optical fiber 120 and then the second optical fiber 120. It leaks into the second medium 140 from the side surface. That is, even if light leakage having a low energy density enters the second medium 140 from the side surface of the second optical fiber 120 having a large diameter, the light leakage having a high energy density from the side surface of the first optical fiber 110 having a small diameter. Does not enter the first medium 130. Therefore, the deterioration of the first medium 130 that can be caused by light leakage is avoided, and the deterioration of the second medium 140 that can be caused by light leakage is suppressed.

[Fifth Example]
Next, a fifth specific example of the structure in the vicinity of the fusion point of the optical device 100 will be described with reference to FIG. FIG. 7 is a cross-sectional view schematically showing the structure near the fusion point of the optical device 100 according to this example.

  In this specific example, a triple clad fiber is used as the first optical fiber 110. That is, the first optical fiber 110 includes a core 111, a first cladding 113 surrounding the core 111, a second cladding 115 surrounding the first cladding 113, and a third cladding 117 surrounding the second cladding 115. In the outer shell removal section 110A, the third cladding 117 is removed, and the second cladding 115 has an outermost shell structure.

  In this specific example, a triple clad fiber is used as the second optical fiber 120. That is, the second optical fiber 120 includes a core 121, a first cladding 123 surrounding the core 121, a second cladding 125 surrounding the first cladding 123, and a third cladding 127 surrounding the second cladding 125. In the outer shell removal section 120A, the third cladding 127 is removed, and the second cladding 125 has an outermost shell structure.

  The outer diameter of the first cladding 113 of the first optical fiber 110, the outer diameter of the second cladding 123 of the second optical fiber 120, the outer diameter of the second cladding 115 of the first optical fiber 110, and the second The following magnitude relationship exists between the outer diameters of the second cladding 125 of the optical fiber 120. Therefore, the second cladding 115 of the first optical fiber 110 intersects with both the first cladding 123 and the second cladding 125 of the second optical fiber 120 at the fusion point P.

The outer diameter of the first cladding 113 of the first optical fiber 110
<Outer diameter of the first cladding 123 of the second optical fiber 120
<Outer diameter of the second cladding 115 of the first optical fiber 110
<Outer Diameter of Second Cladding 125 of Second Optical Fiber 120 In the outer shell removal section 110 </ b> A of the first optical fiber 110, the entire side surface is surrounded by the first medium 130. The first medium 130 is a medium having a refractive index lower than that of the second cladding 115 that is the outermost shell structure of the first optical fiber 110 in the outer shell removal section 110A. For this reason, leakage of light from the first optical fiber 110 to the first medium 130 hardly occurs.

  In particular, in this specific example, the refractive index of the first medium 130 is set to be equal to or lower than the refractive index of the third cladding 117 of the first optical fiber 110. For this reason, the light confined in the second clad 115 by the action of the third clad 117 outside the outer shell removal section 110A is confined in the second clad 115 by the action of the first medium 130 in the outer shell removal section 110A. Therefore, the light that has propagated through the second cladding 115 of the first optical fiber 110 does not leak into the first medium 130 from the side surface of the first optical fiber 110 and does not leak from the end surface of the first optical fiber 110. The light enters the first cladding 123 and the second cladding 125 of the second optical fiber 120.

  In the outer shell removal section 120A of the second optical fiber 120, the side surface of the tip portion is surrounded by the first medium 130, and the side surface of the portion other than the tip portion is surrounded by the second medium 140. The first medium 130 is a medium having a refractive index lower than that of the second cladding 125 that is the outermost shell structure of the second optical fiber 120 in the outer shell removal section 120A. For this reason, leakage of light from the side surface of the second optical fiber 120 to the first medium 130 hardly occurs. On the other hand, the second medium 140 is a medium having a higher refractive index than the second clad 125 that is the outermost shell structure of the second optical fiber 120 in the outer shell removal section 120A. For this reason, leakage of light from the side surface of the second optical fiber 120 to the second medium 140 occurs.

  In the optical device 100 according to this example, the light that has propagated through the second cladding 115 of the first optical fiber 110 is the second optical fiber except for light that enters the first cladding 123 of the second optical fiber 120. After entering the second clad 125 of 120, it leaks into the second medium 140 from the side surface of the second optical fiber 120. That is, even if light leakage having a low energy density enters the second medium 140 from the side surface of the second optical fiber 120 having a large diameter, the light leakage having a high energy density from the side surface of the first optical fiber 110 having a small diameter. Does not enter the first medium 130. Therefore, the deterioration of the first medium 130 that can be caused by light leakage is avoided, and the deterioration of the second medium 140 that can be caused by light leakage is suppressed.

[First application example]
Next, as a first application example of the optical device 100, an application example to a fiber laser apparatus will be described. FIG. 8 is a diagram schematically showing the configuration of the fiber laser device 10 according to this application example.

  A fiber laser device 10 shown in FIG. 8 is a bidirectionally pumped resonator type fiber laser device, which amplifies a laser beam by pump light incident from both directions of an amplification optical fiber 16 and amplifies the laser beam. This is a device for supplying light to the light emitting section 11. As shown in FIG. 8, the fiber laser device 10 includes an optical device 12, an excitation light source 13, an excitation light coupler 14, an FBG (Fiber Bragg Grating) 15, an amplification optical fiber 16, in this order from the laser light emission side. An FBG 17, an excitation light coupler 18, and an excitation light source 19 are provided.

  In the fiber laser device 10, the excitation light emitted from the excitation light source 19 enters the cladding of the amplification optical fiber 16 through the excitation light coupler 18 inserted into the amplification optical fiber 16. Further, the excitation light emitted from the excitation light source 13 enters the cladding of the amplification optical fiber 16 through the excitation light coupler 14 inserted in the amplification optical fiber 16. The pumping light incident on the amplification optical fiber 16 propagates in the amplification optical fiber 16 in both directions.

  The amplification optical fiber 16 is a double clad fiber corresponding to the first optical fiber 110 of the above-described embodiment. In the amplification optical fiber 16, the laser light propagating in the core of the amplification optical fiber 16 is amplified by the pumping light propagating bidirectionally in the amplification optical fiber 16. An optical fiber OF1, which corresponds to the second optical fiber 120 of the above-described embodiment, is fusion spliced to the output side end of the amplification optical fiber 16. An end portion on the emission side of the optical fiber OF1 is connected to the light emission portion 11. As a result, the laser light amplified in the amplification optical fiber 16 propagates to the light emitting portion 11 through the optical fiber OF1.

  The fusion splicing portion is provided with an optical device 12 corresponding to the optical device 100 of the above-described embodiment. Thereby, the residual pumping light propagating through the inner cladding of the amplification optical fiber 16 toward the light emitting portion 11, and the laser light incident on the inner cladding of the amplification optical fiber 16 at the fusion point in the resonator, It can be removed by the optical device 12.

[Second application example]
Next, as a second application example of the optical device 100, an application example to another fiber laser apparatus will be described. FIG. 9 is a diagram schematically showing the configuration of the fiber laser device 20 according to this application example.

  The fiber laser device 20 of the second embodiment shown in FIG. 9 is a MOPA type fiber laser device, and in a PA (Power amplifier), MO (Master) is generated by excitation light incident from both directions of the amplification optical fiber 25. This is a device for amplifying the laser beam emitted from the oscillator 29 and supplying the amplified laser beam to the light emitting unit 21 that emits the laser beam according to the purpose of use. As shown in FIG. 9, the fiber laser device 20 of the second embodiment includes an optical device 22, an excitation light source 23, an excitation light coupler 24, an amplification optical fiber 25, and an excitation light coupling in this order from the laser light emission side. The apparatus 26, the excitation light source 27, the optical device 28, and the MO 29 are provided.

  In the fiber laser device 20 configured as described above, the excitation light emitted from the excitation light source 27 enters the amplification optical fiber 25 via the excitation light coupler 26 inserted into the amplification optical fiber 25. To do. Further, the excitation light emitted from the excitation light source 23 enters the amplification optical fiber 25 via the excitation light coupler 24 inserted into the amplification optical fiber 25. An optical fiber OF3, which corresponds to the second optical fiber 120 of the above-described embodiment, is fusion-spliced to the end of the core of the amplification optical fiber 25 on the incident side. The incident end of the optical fiber OF3 is connected to the MO 29. As a result, the laser light emitted from the MO 29 enters the core of the amplification optical fiber 25 via the optical fiber OF3.

  The amplification optical fiber 25 is a double clad fiber corresponding to the first optical fiber 110 of the above-described embodiment. In the amplification optical fiber 25, the laser light propagating in the core of the amplification optical fiber 25 is amplified by the excitation light propagating in the amplification optical fiber 25. An optical fiber OF2, which corresponds to the second optical fiber 120 of the above-described embodiment, is fusion spliced to the output side end of the amplification optical fiber 25. The end portion on the emission side of the optical fiber OF2 is connected to the light emission portion 21. As a result, the laser light amplified in the amplification optical fiber 25 propagates to the light emitting section 21 through the optical fiber OF2.

  An optical device 22 corresponding to the optical device 100 of the above-described embodiment is provided at the fusion spliced portion between the amplification optical fiber 25 and the optical fiber OF2. Thereby, the residual pumping light propagating through the amplification optical fiber 25 toward the light emitting part 21 can be removed by the optical device 22.

  Further, the excitation light propagating through the amplification optical fiber 25 can also enter the optical fiber OF3 that is fusion-bonded to the end portion on the incident side. For this reason, an optical device 28 corresponding to the optical device 100 of the above-described embodiment is provided in the fusion splicing portion between the amplification optical fiber 25 and the optical fiber OF3. Thereby, the residual pumping light propagating through the amplification optical fiber 25 toward the MO 29 can be removed by the optical device 28.

[Additional Notes]
The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The present invention can be suitably used for an optical amplifying device such as a fiber laser device or a fiber amplifier device.

DESCRIPTION OF SYMBOLS 100 Optical device 110 1st optical fiber 110A Outer shell removal area (1st area)
112 core 114 inner clad (outermost shell structure in the first section)
116 Outer cladding (outer shell structure)
118 Coating (shell structure)
120 Second optical fiber 120A Outer shell removal section (second section)
122 Core 124 Cladding (outermost shell structure in the second section)
126 Coating (outer shell structure)
130 First Medium 140 Second Medium 150 Heat Dissipator 152 Groove P Fusion Point B Boundary (Boundary Between First Optical Fiber and Second Optical Fiber)
10 Fiber Laser Device 20 Fiber Laser Device

Claims (6)

A first optical fiber from which an outer shell structure is removed in a first section including an end face;
A second optical fiber from which the outer shell structure has been removed in a second section including the end face, wherein the end face is fused to the end face of the first optical fiber;
A first medium having a lower refractive index than the outermost shell structure in the first section of the first optical fiber and the outermost shell structure in the second section of the second optical fiber; A first medium surrounding a side surface of the first optical fiber in the entire first section;
A second medium having a refractive index higher than that of the outermost shell structure in the second section of the second optical fiber, wherein a side surface of the second optical fiber is formed in at least a part of the second section. An optical device comprising: a surrounding second medium, wherein light propagates from the first optical fiber toward the second optical fiber;
The outermost shell structure in the first section of the first optical fiber and the outermost shell structure in the second section of the second optical fiber have an intersection at the end face, and An optical device, wherein a diameter of the second optical fiber at a boundary between one medium and the second medium is larger than a diameter of the first optical fiber in the first section.   The optical device according to claim 1, wherein the second section of the second optical fiber has a cylindrical shape with a constant diameter.   The second section of the second optical fiber has a taper shape that decreases in diameter as the distance from the fusion point with the first optical fiber decreases. 3. The optical device according to 2.   The second section of the second optical fiber has a tapered shape whose diameter increases as the distance from the fusion point with the first optical fiber increases. 4. The optical device according to any one of 3 above. It further comprises a radiator with a groove formed,
The first section of the first optical fiber and the second section of the second optical fiber are accommodated in the groove of the radiator,
5. The optical device according to claim 1, wherein the first medium and the second medium are a resin filling the groove.   A fiber laser apparatus comprising the optical device according to claim 1.

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