JP2015126075A - Laser oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of optical elements of a laser oscillator.SOLUTION: A laser oscillator 1 includes a first light source 2, a first optical fiber 3, and a second optical fiber 4. The first light source 2 generates excitation light. The first optical fiber 3 has a first end surface on which the excitation light from the first light source is made incident. The second optical fiber extends from the first light source. The second optical fiber is adhered to the first end surface. The second optical fiber has a reflection film. The reflection film reflects output light generated in the first optical fiber. The second optical fiber is adhered to the first end surface in the reflection film.

Description

  The present invention relates to a laser oscillator.

  Laser oscillators using optical fibers, so-called fiber lasers, are widely used. The laser oscillator oscillates a laser beam by an optical fiber using the excitation light output from the first light source. The optical fiber used for this laser oscillator is formed of fluoride glass such as ZBLAN glass doped with a laser medium such as erbium. Such a fluoride glass, particularly ZBLAN glass, has a problem that it is deliquescent by moisture in the atmosphere, that is, a problem that an end face of the optical fiber is damaged.

  In order to solve this problem, for example, in Patent Document 1, an end cap is joined to the end face of the optical fiber. Thereby, since the end face of the optical fiber is not exposed to the atmosphere, it is possible to prevent the end face of the optical fiber from being deliquescent by moisture in the atmosphere.

  The laser oscillator further includes a mirror for reflecting the output light output from the end of the optical fiber and returning it to the optical fiber in order to amplify the output light generated in the optical fiber.

JP 2007-273842 A

  In the laser oscillator as described above, it is preferable to reduce the number of optical elements in order to reduce the cost and stabilize the optical system.

  An object of the present invention is to reduce the number of optical elements of a laser oscillator.

  A laser oscillator according to an aspect of the present invention includes a first light source, a first optical fiber, and a second optical fiber. The first light source generates excitation light. The first optical fiber has a first end face on which excitation light from the first light source is incident. The second optical fiber extends from the first light source. The second optical fiber is bonded to the first end face. The second optical fiber has a reflective film. The reflective film reflects output light generated in the first optical fiber. The second optical fiber is bonded to the first end face in the reflective film.

  According to this configuration, the output light generated in the first optical fiber is reflected by the reflection film of the second optical fiber and returns to the first optical fiber. Thereby, the output light generated in the first optical fiber can be amplified. In this way, since the reflective film of the second optical fiber serves as a mirror, installation of the mirror can be omitted. As a result, the number of optical elements of the laser oscillator can be reduced.

  Further, since the second optical fiber is bonded to the first end face of the first optical fiber, the first end face of the first optical fiber is not exposed to the atmosphere. For this reason, when the first optical fiber has deliquescence, it is possible to prevent the first end face of the first optical fiber from being deliquescent by moisture in the atmosphere. As a result, the end cap can be omitted. Furthermore, since the first optical fiber and the second optical fiber are bonded, the collimating lens and the condensing lens that have been conventionally installed between the first optical fiber and the second optical fiber should be omitted. Can do.

  Preferably, the first optical fiber is doped with a laser medium. The mass content of the laser medium in the second optical fiber is lower than the mass content of the laser medium in the first optical fiber. The second optical fiber may not be doped with a laser medium.

  Preferably, the laser oscillator further includes a collimating lens or an end cap bonded to the second end surface of the first optical fiber. According to this configuration, since the collimating lens or the end cap is bonded to the second end surface of the first optical fiber, the second end surface of the first optical fiber is not exposed to the atmosphere. For this reason, when the 1st optical fiber has deliquescence, it can prevent that the 2nd end face of the 1st optical fiber deliquesces with the moisture in the atmosphere. The end cap can be omitted by adhering a collimating lens to the second end surface of the first optical fiber.

  Preferably, the collimating lens or the end cap has an antireflection film. The antireflection film prevents reflection of output light generated in the first optical fiber. According to this configuration, when the output light generated in the first optical fiber is output to the outside via the collimator lens or the end cap, it can be output to the outside with lower loss.

  Preferably, the laser oscillator further includes a second light source. The second light source generates excitation light. Excitation light from the second light source is incident on the second end face of the first optical fiber. According to this configuration, since not only the excitation light from the first light source but also the excitation light from the second light source propagates through the first optical fiber, the laser oscillator can output higher-power laser light. .

  Preferably, the first optical fiber and the second optical fiber are bonded to each other by fusion bonding.

  Preferably, the reflective film of the second optical fiber has a reflectance of about 90% to 100% with respect to the output light. According to this configuration, the output light can be amplified more efficiently in the first optical fiber.

  With the laser oscillator according to the present invention, the number of optical elements can be reduced.

Schematic which shows the structure of the laser oscillator which concerns on embodiment. Sectional drawing which shows the detail of the 1st edge part of a 1st optical fiber. Sectional drawing which shows the detail of the 2nd end part of a 1st optical fiber. Sectional drawing which shows the detail of the 1st edge part of the 1st optical fiber which concerns on the modification 1. FIG. Sectional drawing which shows the detail of the 2nd end part of the 1st optical fiber which concerns on the modification 3. FIG. Sectional drawing which shows the detail of the 2nd end part of the 1st optical fiber which concerns on the modification 4. FIG. Sectional drawing which shows the detail of the 2nd end part of the 1st optical fiber which concerns on the modification 5. FIG. Sectional drawing which shows the detail of the 1st edge part of the 1st optical fiber which concerns on the modification 6. FIG. FIG. 10 is a schematic diagram showing a configuration of a laser oscillator according to a modified example 7. Schematic which shows the structure of the laser oscillator concerning the modification 8. FIG.

  Embodiments of a laser oscillator according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of a laser oscillator. In FIG. 1, broken arrows schematically indicate output light. In the following description, “parallel” is a concept that includes not only completely parallel but also substantially parallel.

  As shown in FIG. 1, the laser oscillator 1 includes a first light source 2, a first optical fiber 3, a second optical fiber 4, an end cap 5, and a first collimating lens 6.

The first light source 2 is a device that generates excitation light, and can be constituted by, for example, a lamp or a semiconductor laser. The second optical fiber 4 extends from the first light source 2. FIG. 2 is a cross-sectional view showing details of the first end of the first optical fiber 3. As shown in FIG. 2, the first optical fiber 3 has a first end face 30. Excitation light from the first light source 2 enters the first end face 30. The first optical fiber 3 includes a core 31, a first cladding 32, and a second cladding 33. The first optical fiber 3 is a member that absorbs excitation light and generates laser light. The first optical fiber 3 has flexibility.

The core 31 has a substantially cylindrical shape and includes a laser medium. Specifically, the core 31 is made of a fluoride glass doped with a rare earth element as a laser medium, and preferably a ZBLAN (ZrF ₄ —BaF ₂ —LaF ₃ —AlF ₃ —NaF) glass doped with erbium. Is formed by. The core 31 may be formed of other glass having a higher refractive index than the first cladding 32.

  The first cladding 32 is formed in a substantially cylindrical shape so as to cover the core 31. The first cladding 32 is made of fluoride glass, and is preferably made of ZBLAN glass. The first cladding 32 has a refractive index lower than that of the core 31. The first cladding 32 functions as a waveguide for pumping light, and the pumping light propagates in the first cladding 32. Note that the first cladding 32 may be formed of another glass material having a refractive index lower than that of the core 31.

  The second cladding 33 is formed in a substantially cylindrical shape so as to cover the first cladding 32. The second cladding 33 is made of, for example, a resin, and can be preferably formed of an acrylic resin or the like. The second cladding 33 has a lower refractive index than the first cladding 32.

  The second optical fiber 4 is bonded to the first optical fiber 3. Specifically, the second optical fiber 4 is bonded to the first end face 30 of the first optical fiber 3. Specifically, the second optical fiber 4 is welded to the first end face 30 of the first optical fiber 3. The second optical fiber 4 is a fiber for transmitting excitation light generated by the first light source 2. The second optical fiber 4 has a fiber body 40 and a reflective film 43.

  The fiber body 40 includes a core 41 and a clad 42, and excitation light propagates in the core 41. The core 41 is formed in a substantially cylindrical shape, and the clad 42 is formed in a substantially cylindrical shape so as to cover the core 41. Although not particularly limited, the core 41 is made of quartz glass or the like. The content of the laser medium in the core 41 is lower than the content of the laser medium in the core 31 of the first optical fiber 3, and preferably, the core 41 is not doped with the laser medium. Although not particularly limited, the clad 42 is made of, for example, another glass having a refractive index lower than that of the core 41.

  In order to efficiently introduce the excitation light from the fiber body 40 into the first optical fiber 3, the diameter of the core 41 of the fiber body 40 is preferably equal to or smaller than the diameter of the first cladding 32 of the first optical fiber 3. Further, the value obtained by multiplying the numerical aperture of the core 41 and the diameter of the core 41 of the fiber body 40 is less than or equal to the value obtained by multiplying the numerical aperture of the first cladding 32 and the diameter of the first cladding 32 of the first optical fiber 3. Preferably there is.

The reflective film 43 is formed on the tip surface of the fiber body 40, that is, the end surface of the fiber body 40 on the first optical fiber 3 side. The reflection film 43 has a property of reflecting output light generated in the first optical fiber 3. Specifically, the reflective film 43 has a property of reflecting output light generated when the core 31 of the first optical fiber 3 absorbs excitation light. The reflectivity of the reflection film 43 with respect to the output light is effective when it is higher than the reflectivity of the fiber main body 40, and is preferably closer to 100%, specifically 90% or more. The reflective film 43 is formed by coating the tip surface of the fiber body 40 with, for example, SiO ₂ , TiO ₂ , MgF ₂ or the like by vapor deposition. The excitation light passes through the reflective film 43 and enters the first optical fiber 3.

  The first optical fiber 3 and the second optical fiber 4 are fused by melting the first end face 30 of the first optical fiber 3 and pressing the first optical fiber 3 and the second optical fiber 4 together. The first end face 30 of the first optical fiber 3 and the reflection film 43 of the second optical fiber 4 are welded. The melting points of the fiber body 40 and the reflective film 43 are preferably equal to or higher than the melting point of the first optical fiber 3.

  FIG. 3 is a cross-sectional view showing details of the second end of the first optical fiber 3. As shown in FIG. 3, the end cap 5 is attached to the second end of the first optical fiber 3. Specifically, the end cap 5 is bonded to the second end surface 34 of the first optical fiber 3. Specifically, the end cap 5 is fused to the second end face 34 of the first optical fiber 3. The end cap 5 has an end cap body 51.

  The end cap body 51 of the end cap 5 does not have deliquescence. Specifically, the end cap body 51 can be formed of calcium fluoride or the like. The end cap body 51 is designed to have a size that can cover the entire second end face 34 of the first optical fiber 3. The end cap body 51 preferably has the same linear expansion coefficient as that of the first optical fiber 3 in order to strengthen the bonding with the first optical fiber 3.

  As shown in FIG. 1, the first collimating lens 6 is disposed in the vicinity of the end cap 5. The first collimating lens 6 converts the output light output from the first optical fiber 3 via the end cap 5 into a parallel light state.

[Feature]
The laser oscillator 1 according to this embodiment has the following characteristics.

  The output light generated in the first optical fiber 3 is reflected by the reflection film 43 of the second optical fiber 4 and returns to the first optical fiber 3. As a result, the output light generated in the first optical fiber 3 can be amplified. Thus, since the reflective film 43 of the second optical fiber 4 serves as a mirror, the installation of the mirror can be omitted. As a result, the number of optical elements of the laser oscillator 1 can be reduced.

  Moreover, since the 2nd optical fiber 4 has adhere | attached on the 1st end surface 30 of the 1st optical fiber 3, the 1st end surface 30 of the 1st optical fiber 3 is not exposed to air | atmosphere. For this reason, when the 1st optical fiber 3 has deliquescence, it can prevent that the 1st end surface 30 of the 1st optical fiber 3 deliquesces with the water | moisture content in air | atmosphere. As a result, the end cap can be omitted. Furthermore, since the first optical fiber 3 and the second optical fiber 4 are bonded, a collimating lens and a condensing lens that are conventionally installed between the first optical fiber 3 and the second optical fiber 4, etc. Can also be omitted.

[Modification]
As mentioned above, although embodiment of this invention was described, this invention is not limited to these, A various change is possible unless it deviates from the meaning of this invention.

Modification 1
In the above embodiment, the first optical fiber 3 is a so-called double clad fiber having a core 31 and two clads (a first clad 32 and a second clad 33), but is not particularly limited thereto. For example, the first optical fiber 3 may be a single clad fiber having a core 31 and one clad (first clad 32) as shown in FIG.

  In this case, the excitation light propagates in the core 31. Further, in order to efficiently introduce the excitation light from the fiber body 40 into the first optical fiber 3, the diameter of the core 41 of the fiber body 40 is preferably equal to or smaller than the diameter of the core 31 of the first optical fiber 3. The value obtained by multiplying the numerical aperture of the core 41 of the fiber body 40 by the diameter of the core 41 is preferably equal to or less than the value obtained by multiplying the numerical aperture of the core 31 of the first optical fiber 3 by the diameter of the core 31. .

Modification 2
In the said embodiment, although the end cap main body 51 of the end cap 5 is formed in the substantially cylindrical shape, it is not specifically limited to this. For example, the end cap body 51 may be formed in a rectangular parallelepiped shape.

Modification 3
As shown in FIG. 5, the end cap 5 may further include an antireflection film 52 on the end surface of the end cap body 51 opposite to the first optical fiber 3. The antireflection film 52 has a property of preventing reflection of output light generated in the first optical fiber 3. Specifically, the antireflection film 52 has a property of preventing reflection of output light generated when the core 31 of the first optical fiber 3 absorbs excitation light. The reflectivity of the antireflection film 52 with respect to the output light is effective by making it lower than the reflectivity of the end cap body 51, and is preferably closer to 0%, specifically about 0% or more and 2% or less. It is preferable. The antireflection film 52 is formed, for example, by coating SiO ₂ , TiO ₂ , MgF ₂ or the like on the end surface of the end cap body 51 opposite to the first optical fiber 3 by vapor deposition or the like.

Modification 4
As shown in FIG. 6, the end cap 5 may further include a partial reflection film 53 on the end surface of the end cap body 51 on the first optical fiber 3 side. The partial reflection film 53 has a property of reflecting a part of output light generated in the first optical fiber 3. Specifically, the partial reflection film 53 has a property of reflecting a part of output light generated when the core 31 of the first optical fiber 3 absorbs excitation light. The partial reflection film 53 is formed by coating the end surface of the end cap body 51 on the first optical fiber 3 side with, for example, SiO ₂ , TiO ₂ , or MgF ₂ by vapor deposition or the like.

Modification 5
As illustrated in FIG. 7, the end cap 5 may include both the antireflection film 52 described in the third modification and the partial reflection film 53 described in the fourth modification.

Modification 6
As shown in FIG. 8, the second optical fiber 4 may have an antireflection film 44 for the excitation light on the tip surface of the fiber body 40. The antireflection film 44 has a function of preventing excitation light from the first light source 2 from being reflected. The reflectivity of the antireflection film 44 with respect to the excitation light is effective by making it lower than the reflectivity of the fiber body 40, and is preferably close to 0%, specifically, about 0% or more and 2% or less. Is preferred. The antireflection film 44 is formed by coating the distal end surface of the fiber body 40 with, for example, SiO ₂ , TiO ₂ , MgF ₂ or the like by vapor deposition or the like. In Modification 6, the reflection film 43 is formed on the first optical fiber 3 side rather than the antireflection film 44, but the antireflection film 44 is formed on the first optical fiber 3 side than the reflection film 43. May be.

Modification 7
As shown in FIG. 9, the end cap 5 may be omitted, and the first collimating lens 6 may be attached to the second end of the first optical fiber 3. In this case, the end cap 5 may further have an antireflection film 52 on the end surface of the first collimating lens 6 opposite to the first optical fiber 3 as in the case.

Modification 8
As shown in FIG. 10, a second light source 7, a second collimating lens 8, and a dichroic mirror 9 may be further provided. The second light source 7 is a device that generates excitation light, and can be constituted by, for example, a lamp or a semiconductor laser. Excitation light from the second light source 7 is incident on the second end face 34 of the first optical fiber 3. The excitation light generated by the second light source 7 is output via the third optical fiber 7a. The third optical fiber 7a is preferably not doped with a laser medium.

  The second collimating lens 8 is disposed in the vicinity of the tip of the third optical fiber 7a. The second collimating lens 8 converts the excitation light output from the third optical fiber 7a from a divergent light state to a parallel light state. The first collimating lens 6 also functions as a condenser lens. That is, the first collimating lens 6 condenses the excitation light converted into the parallel light by the second collimating lens 8. The excitation light condensed by the first collimating lens 6 enters the first optical fiber 3 through the end cap 5.

  The dichroic mirror 9 is disposed between the first collimating lens 6 and the second collimating lens 8. The dichroic mirror 9 transmits the excitation light from the second light source 7 and reflects it so as to change the traveling direction of the laser light from the first optical fiber 3.

DESCRIPTION OF SYMBOLS 1 Laser oscillator 2 1st light source 3 1st optical fiber 30 1st end surface 4 2nd optical fiber 43 Reflective film

Claims (8)

A first light source for generating excitation light;
A first optical fiber having a first end surface on which excitation light from the first light source is incident;
A second optical fiber extending from the first light source and bonded to the first end surface;
With
The second optical fiber has a reflective film that reflects output light generated in the first optical fiber, and adheres to the first end face in the reflective film.
Laser oscillator. The first optical fiber is doped with a laser medium;
The mass content of the laser medium in the second optical fiber is lower than the mass content of the laser medium in the first optical fiber.
The laser oscillator according to claim 1.   The laser oscillator according to claim 2, wherein the second optical fiber is not doped with the laser medium.   4. The laser oscillator according to claim 1, further comprising a collimating lens or an end cap bonded to the second end face of the first optical fiber. 5. The collimating lens or the end cap has an antireflection film for preventing reflection of output light generated in the first optical fiber on an end surface opposite to an end surface bonded to the second end surface of the first optical fiber. ,
The laser oscillator according to claim 4. A second light source for generating excitation light;
Excitation light from the second light source is incident on the second end face of the first optical fiber;
The laser oscillator according to claim 4 or 5.   The laser oscillator according to claim 1, wherein the first optical fiber and the second optical fiber are bonded to each other by fusion bonding.   The laser oscillator according to claim 1, wherein the reflection film of the second optical fiber has a reflectance of 90% to 100% with respect to the output light.

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