JP2015198125A - fiber laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser device that can emit laser beams of plural wavelengths with a simpler and smaller configuration than prior arts.SOLUTION: A laser device has an exciting light source part for emitting first excitation light of a first wavelength and second excitation light of a second wavelength, a first optical fiber in which first dopant is doped in a core portion, and a second optical fiber which is disposed to be farther from the exciting light source part in the optical axis direction than the first optical fiber, and in which second dopant is doped in a core portion. Upon incidence of the first excitation light and the second excitation light, the first optical fiber absorbs a part of the first excitation light, excites the first dopant to generate a first laser beam of a third wavelength, and also emits the first excitation light, the second excitation light and the first laser beam. Upon incidence of the first excitation light, the second excitation light and the first laser beam, the second optical fiber absorbs a part of the second excitation light, excites the second dopant to generate a second laser beam of a fourth wavelength, and emits the first excitation light, the second excitation light, the first laser beam and the second laser beam.

Description

  The present invention relates to a fiber laser device.

  Currently, fluorescent microscopes equipped with a laser light source as an excitation light source are commercially available. An excitation light source of a fluorescence microscope is desired to emit light having a wavelength that is absorbed with high efficiency by a fluorescent material and that does not overlap with the wavelength of fluorescence and that has a narrow wavelength width. Further, as an excitation light source for a fluorescence microscope, a laser light source capable of emitting light of a plurality of wavelengths is required so that various fluorescent substances can be excited (see Patent Document 1 below).

JP 2001-290078 A

  In order to realize a light source capable of emitting light of a plurality of wavelengths, conventionally, individual light emitting elements have to be mounted corresponding to the wavelength of light desired to be obtained. In addition, the light emitted from each light emitting element has to be emitted after being synthesized through an optical system. As the types of necessary light wavelengths increase, the number and size of optical systems and light-emitting elements necessary for synthesizing light increase. For this reason, when it was going to implement | achieve the laser light source which can inject | emit the light of a several wavelength, there existed a subject that an apparatus structure became complicated and enlarged.

  The present invention has been made in view of the above problems, and an object of the present invention is to realize a laser device that can emit laser beams of a plurality of wavelengths with a simpler and smaller configuration than the conventional one.

  This invention implement | achieves said subject using a fiber laser apparatus. The configuration of the fiber laser device will be described later in the “Detailed Description of the Invention” section.

The fiber laser device according to the present invention is
An excitation light source unit that emits first excitation light of a first wavelength and second excitation light of a second wavelength;
A first optical fiber having a core portion doped with a first dopant;
The second optical fiber is disposed at a position farther in the optical axis direction from the excitation light source part than the first optical fiber, and the core part is doped with a second dopant,
When the first excitation light and the second excitation light are incident, the first optical fiber absorbs a part of the first excitation light to excite the first dopant, Generating laser light and emitting the first excitation light, the second excitation light, and the first laser light;
The second optical fiber absorbs a part of the second excitation light when the first excitation light, the second excitation light, and the first laser light emitted from the first optical fiber are incident. Then, the second dopant is excited to generate a second laser light having a fourth wavelength, and the first excitation light, the second excitation light, the first laser light, and the second laser light are emitted. It is characterized by that.

  According to the above configuration, it is possible to realize a laser apparatus that can emit light of a larger number of wavelengths than the types of wavelengths that the excitation light source unit can emit. Further, since the multi-wavelength light is synthesized by connecting the first optical fiber and the second optical fiber in series, a complicated optical system is not required for synthesizing the light, and a simple configuration can be realized.

  Here, the first dopant may be composed of Pr, and the second dopant may be composed of Sm.

  There are many wavelength bands of the fluorescence spectrum of Pr that are not easily absorbed by Sm. On the other hand, the wavelength band of the fluorescence spectrum of Sm includes a region included in the wavelength band absorbed by Pr. For this reason, the dopant doped in the core part of the first optical fiber close to the excitation light source part is Pr, and the dopant doped in the core part of the second optical fiber located downstream from the first optical fiber is Sm. Thus, the laser light generated in both optical fibers can be extracted with high efficiency.

  Sm constituting the second dopant may not be excited by the light of the first wavelength, the third wavelength, or the fourth wavelength, but may be excited by the light of the second wavelength. As an example, the first wavelength can be 445 nm, the second wavelength can be 405 nm, the third wavelength can be 635 nm, and the fourth wavelength can be 560 nm.

  Pr has low absorptance for light having a wavelength of about 415 nm or less and light having a wavelength of about 610 nm or more. On the other hand, Sm has low absorptance with respect to light having a wavelength in the vicinity of 445 nm (for example, 430 nm to 450 nm or less) and light having a wavelength of 500 nm or more.

  The wavelength of the first excitation light (first wavelength) is set to a wavelength included in a wavelength band in which the absorptance at Sm is low and the absorptance at Pr is high, and is generated by exciting Pr with the light of the first wavelength. The wavelength (third wavelength) of the first laser light is set to a wavelength included in a wavelength band having low absorptance in Pr and Sm. Further, the wavelength of the second excitation light (second wavelength) is set to a wavelength included in a wavelength band in which the absorptance at Pr is low and the absorptance at Sm is high, and is generated by excitation of Sm by the light of the second wavelength. The wavelength of the second laser light (fourth wavelength) to be used is a wavelength included in a wavelength band having a low absorptance in Sm.

  Thereby, among the first excitation light having the first wavelength, the light that is not absorbed by Pr is hardly absorbed by Sm in the second optical fiber, and is emitted from the second optical fiber. Also, the first laser light having the third wavelength generated by the first optical fiber is not easily absorbed by Sm in the second optical fiber, and is emitted from the second optical fiber.

  Further, since the second excitation light indicating the second wavelength is difficult to be absorbed by Pr, the second excitation light is guided to the second optical fiber through the first optical fiber while maintaining a high output. Then, the second excitation light is absorbed by Sm doped in the core portion of the second optical fiber, and second laser light having a fourth wavelength is generated. The second laser light having the fourth wavelength is difficult to be absorbed by Sm doped in the core portion of the second optical fiber. As a result, the second excitation light remaining without being absorbed by Sm in the second optical fiber, and the first excitation light, the first laser light, and the second laser light that are hardly absorbed by Sm, Ejected from the second optical fiber.

In addition to the above configuration, the first wavelength, the second wavelength, the third wavelength, and a spacer that transmits light of the fourth wavelength,
The first optical fiber and the second optical fiber may be connected via the spacer.

  If the first optical fiber and the second optical fiber are completely in close contact with each other, the reflection characteristics at the end face change. On the other hand, if the distance between the end faces of both optical fibers is too large, the light emitted from the first optical fiber toward the second optical fiber leaks without being guided to the core of the second optical fiber. The amount of light that is generated increases, and the amount of light that is extracted decreases.

  When the first optical fiber and the second optical fiber are connected to each other, if there is a gap having a wavelength longer than that, the optical fiber is optically separated. Therefore, a spacer having a width that is equal to or greater than the wavelength and that can suppress the amount of light leakage to a minimum (for example, 1 μm to 2 μm) is interposed between the first optical fiber and the second optical fiber. By connecting both optical fibers, it is possible to increase the light extraction efficiency while suppressing the influence on the reflection characteristics.

For example, the following configuration can be adopted for the fiber laser device. That is,
A first end that is an end of the first optical fiber on the excitation light source side, and a second end opposite to the first end of the first optical fiber, or the first light of the second optical fiber. A first resonator provided at a first end which is an end portion on a fiber side;
A second resonator provided at the second end of the first optical fiber or the first end of the second optical fiber and a second end opposite to the first end of the second optical fiber. And
The first resonator resonates the light of the third wavelength to generate the first laser light, and transmits the light of the first wavelength and the light of the second wavelength,
The second resonator resonates the fourth wavelength light to generate the first laser light, and transmits the first wavelength light, the second wavelength light, and the third wavelength light. Can be.

The fiber laser apparatus can also employ the following configuration. That is,
A first end that is an end of the first optical fiber on the excitation light source side, and a second end opposite to the first end of the first optical fiber, or the first light of the second optical fiber. A first resonator provided at a first end which is an end portion on a fiber side;
A second resonator provided at the first end of the first optical fiber and an end of the second optical fiber opposite to the end of the first optical fiber;
The first resonator resonates the light of the third wavelength to generate the first laser light, and transmits the light of the first wavelength and the light of the second wavelength,
The second resonator resonates the fourth wavelength light to generate the first laser light, and transmits the first wavelength light, the second wavelength light, and the third wavelength light. And
The first resonator and the second resonator may be shared by the first end of the first optical fiber.

  According to the above configuration, since the first resonator and the second resonator are shared at the first end of the first optical fiber, the number of optical members constituting the reflecting surface can be suppressed, and the manufacturing can be performed. Simplification of the process and reduction of manufacturing costs can be achieved.

Further, in addition to the above configuration, the optical fiber further includes a third optical fiber disposed at a position farther in the optical axis direction from the excitation light source unit than the second optical fiber and doped with the second dopant in the core unit,
When the first excitation light, the second excitation light, the first laser light, and the second laser light emitted from the second optical fiber are incident, the third optical fiber receives the second excitation light. And absorbing the first dopant to excite the second dopant to generate a third laser beam having a fifth wavelength, and the first excitation light, the second excitation light, the first laser light, and the second laser. Light and the third laser beam may be emitted.

  According to the above configuration, although there are two types of wavelengths of the excitation light emitted from the excitation light source unit, it is possible to emit laser light having five types of wavelengths. For example, when the first dopant is composed of Pr and the second dopant is composed of Sm, the first wavelength is 445 nm, the second wavelength is 405 nm, the third wavelength is 635 nm, the fourth wavelength is 594 nm, and the fifth The wavelength can be 560 nm.

  In addition, the wavelength of the excitation light emitted from the excitation light source unit is not limited to two types, and three or more types may exist.

  According to the fiber laser device of the present invention, a laser device capable of emitting laser beams of a plurality of wavelengths with a simpler and smaller configuration than the conventional one is realized.

It is drawing which shows typically the structure of the fiber laser apparatus of 1st embodiment. It is drawing which shows typically the structure which looked at the 1st optical fiber body in the optical axis direction. It is typical sectional drawing when a 1st optical fiber body is cut | disconnected by the AA in FIG. 2A. It is a figure for demonstrating the installation aspect of an optical fiber body. It is a graph which shows the excitation spectrum and emission spectrum of Pr and Sm. It is drawing which shows the spectrum of the light extracted from the fiber laser apparatus of 1st embodiment. It is drawing which shows typically the structure of the fiber laser apparatus of 2nd embodiment. It is drawing which shows typically the structure of the fiber laser apparatus of 3rd embodiment.

  The configuration of each embodiment of the fiber laser device of the present invention will be described with reference to the drawings. In each figure, the dimensional ratio in the drawing does not necessarily match the actual dimensional ratio.

[First embodiment]
FIG. 1 is a drawing schematically showing the configuration of the fiber laser device of the first embodiment. A fiber laser device 1 shown in FIG. 1 includes an excitation light source unit 10, a first optical fiber 20, and a second optical fiber 30. The second optical fiber 30 is disposed farther from the excitation light source unit 10 in the direction of the optical axis 2 than the first optical fiber 20.

  In the following, of the ends of the first optical fiber 20, the end close to the excitation light source unit 10 in the direction of the optical axis 2 is referred to as “first end 20 a” and is opposite to the first end 20 a. The end is referred to as “second end 20b”. Similarly, of the end portions of the second optical fiber 30, the end portion on the side close to the first optical fiber 20 in the direction of the optical axis 2 is referred to as “first end 30 a”, and the end opposite to the first end 30 a. The part is referred to as “second end 30b”.

(Excitation light source unit 10)
In the present embodiment, the excitation light source unit 10 emits excitation light having a wavelength λ1 (hereinafter referred to as “first excitation light”) and excitation light having a wavelength λ2 (hereinafter referred to as “second excitation light”). A second excitation light source 12 that emits "excitation light". The wavelength λ1 corresponds to the “first wavelength”, and the wavelength λ2 corresponds to the “second wavelength”. As an example, λ1 = 445 nm and λ2 = 405 nm can be set.

  The excitation light source unit 10 includes a coupling optical system (13, 14, 15) and a dichroic mirror 16. The dichroic mirror 16 is designed to transmit at least light having a wavelength λ1 and reflect at least light having a wavelength λ2. The coupling optical system 13 is an optical system for guiding the first excitation light emitted from the first excitation light source 11 to the dichroic mirror 16, and is composed of, for example, a collimating lens. The coupling optical system 14 is an optical system for guiding the second excitation light emitted from the second excitation light source 12 to the dichroic mirror 16, and is composed of, for example, a collimating lens. The coupling optical system 15 is an optical system for guiding the light emitted from the dichroic mirror 16 to the core portion 21 of the first optical fiber 20, and is composed of, for example, a condenser lens.

  By configuring the pumping light source unit 10 as described above, when the first pumping light source 11 and the second pumping light source 12 are driven, the first pumping light having the wavelength λ1 and the second pumping light having the wavelength λ2 are combined to form the first optical fiber. It is incident on 20 core portions 21. The pumping light source unit 10 may have any configuration as long as the first pumping light having the wavelength λ1 and the second pumping light having the wavelength λ2 are combined and incident on the core unit 21 of the first optical fiber 20. The configuration illustrated in FIG. 1 is merely an example. For example, when the distance between the dichroic mirror 16 and the first optical fiber 10 is narrow, the coupling optical system 15 may be omitted.

(First optical fiber 20, second optical fiber 30)
The first optical fiber 20 includes a core portion 21, a cladding portion 22 made of a material having a lower refractive index than the core portion 21, and a covering portion 23 that is disposed outside the cladding portion 22 and covers the cladding portion 22. . The core portion 21 is doped with a predetermined first dopant (herein referred to as Pr).

  FIG. 2A is a drawing schematically showing a configuration in which the first optical fiber 20 (first optical fiber body 26 described later) is viewed in the direction of the optical axis 2. In FIG. 2A, a ferrule 25 for inserting the first optical fiber 20 therein is also illustrated.

  The ferrule 25 is formed in a cylindrical shape, and the first optical fiber 20 is inserted therein. An adhesive layer 24 is interposed between the first optical fiber 20 and the ferrule 25, and the first optical fiber 20 and the ferrule 25 are fixed by the adhesive layer 24. The adhesive layer 24 is composed of a general epoxy adhesive. Hereinafter, the first optical fiber 20, the adhesive layer 24, and the ferrule 25 are collectively referred to as a “first optical fiber body 26”. FIG. 2B schematically shows a cross-sectional view of the optical fiber body 26 taken along the line AA in FIG. 2A.

  The second optical fiber 30 includes a core part 31, a clad part 32 made of a material having a lower refractive index than the core part 31, and a covering part 33 that is disposed outside the clad part 32 and covers the clad part 32. . The core portion 31 is doped with a predetermined second dopant (here, Sm).

  The second optical fiber 30 is also inserted into a ferrule 25 formed in a cylindrical shape, and is fixed to the ferrule 25 by an adhesive layer 24. Since the structure is the same as that of the first optical fiber 20 shown in FIGS. 2A and 2B, the description is omitted. Hereinafter, the second optical fiber 30, the adhesive layer 24, and the ferrule 25 are collectively referred to as a “second optical fiber body 36”.

  A spacer 60 is disposed between the first optical fiber body 26 and the second optical fiber body 36. The spacer 60 is provided for the purpose of placing the first optical fiber 20 and the second optical fiber 30 apart from each other in an optical sense, and is composed of an air layer or a translucent member. The spacer 60 exhibits extremely high translucency with respect to light of at least wavelengths λ1 and λ2 and wavelength λ3 described later.

  FIG. 3 is a view for explaining an installation mode of the optical fiber bodies (26, 36). Fig.3 (a) is drawing which shows typically the state which installed the two optical fiber bodies (26,36). FIG. 3B is a drawing schematically showing an enlarged installation mode of the optical fiber body 26, and corresponds to the drawing when the drawing of FIG. 3A is viewed in the direction of the optical axis 2. FIG. .

  As will be described later, in the fiber laser device 1, light of a plurality of wavelengths is incident on the core portion 31 of the second optical fiber 30 from the core portion 21 of the first optical fiber 20. For this reason, in order to reduce the loss of light between the core portions (21, 31) as much as possible, it is required to perform position adjustment (alignment) between the core portions (21, 31) as accurately as possible. .

  As will be described later, in the present embodiment, a reflective film 52 is formed on the second end 20 b of the first optical fiber 20, and a reflective film 53 is formed on the first end 30 a of the second optical fiber 30. Has been. These reflection films are designed so as to exhibit predetermined reflection characteristics. Here, when the second end 20b of the first optical fiber 20 and the first end 30a of the second optical fiber 30 come into contact with each other, that is, when both reflection films (52, 53) come into contact with each other, The reflection characteristics of each reflection film (52, 53) will be affected. On the other hand, if the space between the first optical fiber 20 and the second optical fiber 30 is too large, the core portion 31 of the second optical fiber 30 out of the light emitted from the second end 20 b of the first optical fiber 20. The proportion of light that leaks outside without being incident on the light increases.

  Therefore, the fiber laser device 1 includes a spacer 60 for the purpose of separating the first optical fiber 20 and the second optical fiber 30 in an optical sense. Here, “separated in an optical sense” means that the light is separated by more than the length of the wavelength of the traveling light with respect to the traveling direction of the light. Therefore, the spacer 60 having a width of, for example, about 1 μm to 2 μm is used from the viewpoint of making the light transmission efficiency between the two optical fibers (20, 30) as high as possible without bringing both the optical fibers (20, 30) into contact. It is preferable to arrange.

  Both optical fiber bodies (26, 36) can be configured to be held by a predetermined holding member 62, for example. For example, as shown in FIG. 3B, the holding member 62 has a shape that becomes narrower as it goes downward, and has a groove 63 that extends in the direction of the optical axis 2. Under this configuration, the optical fiber body (26, 36) is placed on the holding member 62, so that the position of the core portion 21 of the first optical fiber 20 and the core portion 31 of the second optical fiber 30 can be easily adjusted. Can be done.

  In addition, in order to guide the light emitted from the core portion 21 of the first optical fiber 20 to the core portion 31 of the second optical fiber 30 as efficiently as possible, the misalignment between the center of the core portion 21 and the center of the core portion 31 is possible. The amount is preferably within 1/10 of the diameter of the core (21, 31).

  The holding member 62 can be formed of, for example, a cylindrical member in addition to the shape shown in FIG. In this case, the holding member 62 may be formed of a cylindrical member having an inner diameter that substantially corresponds to the outer diameter of the first optical fiber body 26 and the second optical fiber body 36. According to such a configuration, the first optical fiber body 26 is inserted from one end face of the holding member 62 and the second optical fiber body 36 is inserted from the other end face, so that the center of the core portion 21 and the core portion 31 are inserted. The center position can be easily adjusted.

  As an example, the first optical fiber body 25 and the second optical fiber body 26 are configured with an outer diameter of about 2.5 mm ± 0.5 μm, and the inner diameter of the cylindrical portion provided in the holding member 62 is 2.5 mm + 0.5 to 1 μm. It can be configured with a degree.

  As described above, the core portion 21 of the first optical fiber 20 is doped with Pr. On the other hand, the core portion 31 of the second optical fiber 30 is doped with Sm.

  FIG. 4 is a graph showing excitation and emission spectra of Pr and Sm. Rare earth elements such as Pr and Sm have the property of absorbing light of a predetermined wavelength and being excited by the absorption of this light to emit fluorescence having a wavelength different from that of the absorbed light. The excitation spectrum corresponds to a spectrum in which the intensity of light that can be absorbed is shown for each wavelength, and light having a wavelength with a higher intensity is more easily absorbed, and Pr and Sm are easily excited by such absorption to emit fluorescence. The emission spectrum corresponds to a spectrum showing the intensity of fluorescence emitted by excitation of Pr and Sm for each wavelength.

  According to FIG. 4, it can be seen that Pr and Sm have different wavelength bands of light exhibiting a high absorption rate. For example, Pr has a low absorptance for light with a wavelength of about 415 nm or less and light with a wavelength of about 610 nm or more. On the other hand, Sm has low absorptance with respect to light having a wavelength in the vicinity of 445 nm (for example, 430 nm to 450 nm or less) and light having a wavelength of 500 nm or more.

  A reflective film 51 is formed on the first end 20a of the first optical fiber 20, and a reflective film 52 is formed on the second end 20b. Similarly, a reflective film 53 is formed on the first end 30a of the second optical fiber 30, and a reflective film 54 is formed on the second end 30b.

  The reflective film 51 has a high transmittance (for example, 90% or more) with respect to the wavelength λ1 of the light emitted from the first excitation light source 11 and the wavelength λ2 of the light emitted from the second excitation light source 12. . Further, it has an extremely high reflectance (for example, 99% or more) with respect to the predetermined wavelength λ3. This wavelength λ3 is a wavelength included in the wavelength band of fluorescence emitted when Pr is excited.

  The reflective film 52 has a high transmittance (for example, 90% or more) with respect to the wavelength λ1 of the light emitted from the first excitation light source 11 and the wavelength λ2 of the light emitted from the second excitation light source 12. . Moreover, it has a predetermined reflectance (for example, 95% ± 1%) with respect to the wavelength λ3.

  With such a configuration, the reflective film 51 and the reflective film 52 constitute a resonator (corresponding to a “first resonator”) for light having a wavelength λ3. This wavelength λ3 corresponds to the “third wavelength”.

  In the above example, the first excitation light having a wavelength of 445 nm and the second excitation light having a wavelength of 405 nm are incident on the core portion 21 of the first optical fiber 20 from the excitation light source unit 10. As shown in FIG. 4, Pr has a low absorptance for light of about 415 nm or less, but shows a somewhat high absorptance for light of about 420 nm or more and about 500 nm or less. For this reason, in the core part 21 of the first optical fiber 20, the second excitation light having a wavelength of 405 nm (λ2) is not absorbed or hardly absorbed, while the first excitation light having a wavelength of 445 nm (λ1) is absorbed to some extent. When Pr absorbs this first excitation light, it emits fluorescence having a wavelength distribution as shown in the emission spectrum of FIG.

  Here, since the reflective film 52 has a high transmittance with respect to the light of the wavelengths λ1 and λ2, the second excitation light that has passed through the core portion 21 of the first optical fiber 20 and the core portion 21 Part of the first excitation light remaining without being absorbed is transmitted through the reflective film 52 and guided to the incident surface 30 a of the second optical fiber 30. Of the fluorescence emitted from the first optical fiber 20, light having a specific wavelength is reflected by the reflective film 52 without loss. Here, light of wavelength λ3 is reflected by the reflective film 52. At this time, if the wavelength λ3 is the peak wavelength of fluorescence corresponding to the energy transition of electrons, light in a predetermined wavelength band including the wavelength λ3 may be reflected by the reflective film 52.

  The fluorescence having the wavelength λ <b> 3 travels toward the first end 20 a of the first optical fiber 20 when reflected by the reflective film 52. The reflective film 51 provided on the first end 20a has an extremely high reflectance with respect to light having the wavelength λ3. Therefore, when this fluorescence reaches the reflection film 51, the component of the wavelength λ3 is reflected without loss and proceeds again toward the reflection film 52.

  Hereinafter, when reflection is repeated between the reflective film 51 and the reflective film 52 and a predetermined oscillation condition is satisfied, laser light having a wavelength λ3 (hereinafter referred to as “first laser light”) is generated. Light passes through the reflective film 52 and enters the first end 30 a of the second optical fiber 30.

  The reflection characteristics of the reflection film 51 and the reflection film 52 are designed according to the fluorescence spectrum and the wavelength of the laser beam to be obtained. However, the first optical fiber 20 is preferably configured to generate laser light having a wavelength with low absorptance in the dopant (here, Sm) doped in the core portion 31 of the second optical fiber 30. This is because even if laser light is generated in the first optical fiber 20, the second light can be used as long as this wavelength is included in the wavelength band absorbed by the dopant doped in the core portion 31 of the second optical fiber 30. This is because the laser beam having this wavelength cannot be extracted with high output because it is absorbed into the fiber 30 and travels through the second optical fiber 30.

  Further, the reflection characteristics of the reflection film 51 and the reflection film 52 preferably have a high reflectance only at the wavelength of the laser beam to be obtained (here, λ3), and have a very low reflectance at other wavelengths. When such a film is formed, the number of films is extremely increased and the film thickness is increased. For this reason, it has the highest reflectivity with respect to the light of wavelength λ3, shows a predetermined reflectivity in the vicinity of wavelength λ3, but has a lower reflectivity than wavelength λ3, and has a wavelength away from wavelength λ3. On the other hand, a configuration that hardly reflects light may be used. Even in such a case, in the process of repeating reflection between the reflective film 51 and the reflective film 52, the intensity of the wavelength λ3 is selectively increased and laser oscillation can be performed.

  As an example, the third wavelength λ3 can be set to 635 nm. According to FIG. 4, the absorptance in Sm is very small (almost 0) with respect to light of 635 nm.

  The reflective film 53 is generated by the wavelength λ 1 of the first excitation light emitted from the first excitation light source 11, the wavelength λ 2 of the second excitation light emitted from the second excitation light source 12, and the first optical fiber 20. It has a high transmittance (for example, 90% or more) with respect to the light of wavelength λ3 of the first laser light. Further, it has an extremely high reflectance (for example, 99.5% or more) with respect to the predetermined wavelength λ4. This wavelength λ4 is a wavelength included in the wavelength band of light emitted when Sm is excited.

  The reflective film 54 has a high transmittance (for example, 90% or more) with respect to light having wavelengths λ1, λ2, and λ3. Further, it has a predetermined reflectance (for example, 95% ± 1%) with respect to light of λ4.

  In such a configuration, the reflective film 53 and the reflective film 54 constitute a resonator (corresponding to a “second resonator”) for light having a wavelength λ4. This wavelength λ4 corresponds to the “fourth wavelength”.

  In the above example, the first excitation light having a wavelength of 445 nm (λ1) and the second excitation light having a wavelength of 405 nm (λ2) that have passed through the first optical fiber 20 and the wavelength 635 nm (λ3) generated by the first optical fiber 20 are used. The first laser light is incident on the core portion 31 of the second optical fiber 30. As shown in FIG. 4, Sm has a low absorptance with respect to light having a wavelength near 445 nm (for example, 430 nm to 450 nm) and light having a wavelength of 500 nm or more, and to light having a wavelength near 405 nm (for example, wavelength 395 nm to 415 nm). Absorption rate is high.

  Therefore, in the core portion 31 of the second optical fiber 30, the first excitation light having a wavelength of 445 nm and the first laser light having a wavelength of 635 nm are not absorbed or hardly absorbed, whereas the second excitation light having a wavelength of 405 nm is absorbed to some extent. The And Sm will emit the fluorescence which has a wavelength distribution as shown by the emission spectrum of FIG. 4, if this 2nd excitation light is absorbed.

  Here, since the reflection film 54 has a high transmittance with respect to the light of the wavelength λ1, the wavelength λ2, and the wavelength λ3, the first excitation light that has passed through the core portion 31 of the second optical fiber 30, A portion of the second excitation light remaining without being absorbed in the core portion 31 is transmitted through the reflection film 54 and extracted outside the fiber laser device 1. Of the fluorescence emitted from the second optical fiber 30, light having a specific wavelength is reflected by the reflective film 54 without loss. Here, light of wavelength λ4 is reflected by the reflective film 54. At this time, if the wavelength λ4 is the peak wavelength of fluorescence corresponding to the energy transition of electrons, light in a predetermined wavelength band including the wavelength λ4 may be reflected by the reflective film 54.

  Fluorescence having the wavelength λ4 travels toward the first end 30a of the second optical fiber 30 when reflected by the reflective film 54. The reflective film 53 provided on the first end 30a has an extremely high reflectance with respect to light having the wavelength λ4. For this reason, when the fluorescence reaches the reflection film 53, the component of the wavelength λ4 is reflected without loss and proceeds again toward the reflection film 54.

  Thereafter, when reflection is repeated between the reflection film 53 and the reflection film 54 and a predetermined oscillation condition is satisfied, a laser beam having a wavelength λ4 (hereinafter referred to as “second laser beam”) is generated, and this second laser is generated. Light passes through the reflective film 54 and is extracted outside the fiber laser device 1.

  The reflection characteristics of the reflection film 53 and the reflection film 54 are also designed according to the fluorescence spectrum and the wavelength of the laser beam to be obtained. At this time, it is preferable that the reflection characteristics of the reflection film 53 and the reflection film 54 have a high reflectance only at the wavelength of the laser beam to be obtained (here, λ4) and an extremely low reflectance at other wavelengths. However, when such a film is formed, the number of films is extremely increased and the film thickness is increased. For this reason, it has the highest reflectivity with respect to the light of wavelength λ4, shows a predetermined reflectivity in the vicinity of wavelength λ4, but has a lower reflectivity than wavelength λ4, and has a wavelength away from wavelength λ4. On the other hand, a configuration that hardly reflects light may be used. Even in such a case, in the process of repeating reflection between the reflective film 53 and the reflective film 54, the intensity of the wavelength λ4 is selectively increased and laser oscillation can be performed.

  According to the above configuration, only by preparing the first excitation light source 11 that emits light of wavelength λ1 and the second excitation light source 12 that emits light of wavelength λ2, four types of wavelengths λ1, λ2, λ3, and λ4 are prepared. A fiber laser device 1 that can extract light of a wavelength is realized. That is, according to the fiber laser device 1, it is possible to realize a laser device that can emit light of more types of wavelengths than the types of wavelengths that the excitation light source unit 10 can emit.

  Further, since the multi-wavelength light is synthesized by connecting the first optical fiber 20 and the second optical fiber 30 in series, a complicated optical system is not required for synthesizing the light, and can be realized with a simple configuration. .

  Hereinafter, a specific configuration of the embodiment will be described.

  The first excitation light source 11 is composed of a laser diode element that emits light having a wavelength λ1 = 445 nm. The second excitation light source 12 is composed of a laser diode element that emits light having a wavelength λ2 = 405 nm. Both light sources (11, 12) are arranged so that the optical axis of the first excitation light emitted from the first excitation light source 11 and the optical axis of the second excitation light emitted from the second excitation light source 12 are orthogonal to each other. Is done.

  The coupling optical system 13 is composed of a collimating lens. By the coupling optical system 13, the first excitation light having the wavelength λ 1 emitted from the first excitation light source 11 is incident on the dichroic mirror 16 as parallel light.

  The coupling optical system 14 is composed of a collimating lens. By the coupling optical system 14, the second excitation light having the wavelength λ <b> 2 emitted from the second excitation light source 12 is incident on the dichroic mirror 16 as parallel light. At the time of incidence on the dichroic mirror 16, the optical axis of the first excitation light and the optical axis of the second excitation light are orthogonal.

  The dichroic mirror 16 is made of, for example, a dielectric multilayer film, and is designed to transmit light having a wavelength λ1 (445 nm) and reflect light having a wavelength λ2 (405 nm). The reflecting surface of the dichroic mirror 16 is arranged with an inclination of 45 ° with respect to the optical axis of the first excitation light and the optical axis of the second excitation light at the time of incidence on the dichroic mirror 16. As a result, the first excitation light having the wavelength λ1 is transmitted through the dichroic mirror 16 and continuously travels in the traveling direction at the time of entering the dichroic mirror 16. On the other hand, the second excitation light of wavelength λ2 is reflected by the dichroic mirror 16 and travels in the same direction as the first excitation light. Thereby, the first excitation light and the second excitation light are combined on the optical axis 2 and guided to the first end 20 a of the first optical fiber 20.

  As an example, the first excitation light and the second excitation light are each incident on the core portion 21 of the first optical fiber 20 with an output of about 0.5 W.

  The first optical fiber 20 is made of fluoride glass in which the core portion 21 has a diameter of 6 μm and Pr ions are added to the core portion 21. The length in the direction of the optical axis 2 of the first optical fiber 20 is 28 mm. The absorptance α of the Pr ion with respect to light having a wavelength λ1 (445 nm) is α / 0.05 / mm. In this embodiment, about 75% of light having a wavelength λ1 (445 nm) can be absorbed by the core portion 21. On the other hand, Pr ions hardly absorb light having a wavelength of λ2 (405 nm).

  The first optical fiber 10 includes a reflective film 51 at a first end 10a and a reflective film 52 at a second end 10b. The reflective film 51 is designed so that the transmittance with respect to light of wavelength λ1 (445 nm) and wavelength λ2 (405 nm) is 99% or more, and the reflectance with respect to light of wavelength λ3 (635 nm) is 99.5% or more. ing. The reflective film 52 is designed so that the transmittance with respect to the light with the wavelength λ1 and the wavelength λ2 is 98% or more and the reflectance with respect to the light with the wavelength λ3 is about 95%.

  With this configuration, after the light with the wavelength λ3 is repeatedly reflected between the reflective film 51 and the reflective film 52, laser oscillation is performed, and the first laser light with the wavelength λ3 (635 nm) is generated. In the above configuration, the first excitation light having the wavelength λ1 is not completely absorbed by the core portion 21, and a part of the light is emitted from the second end 20b. The second excitation light having the wavelength λ2 and the first laser light having the wavelength λ3 are also emitted from the second end 20b.

  As an example of the output of light emitted from the second end 20b of the first optical fiber 20, the optical output of the wavelength λ1 is 0.13 W, the optical output of the wavelength λ2 is 0.5 W, and the optical output of the wavelength λ3 is 0. 13W. At this time, the laser efficiency (ratio of the obtained laser light energy to the absorbed excitation light energy) in the first optical fiber 20 was about 0.35.

  The second optical fiber 30 is made of a fluoride glass in which the core portion 31 has a diameter of 8 μm and Sm ions are added to the core portion 31. The length of the second fiber 30 in the direction of the optical axis 2 is 50 mm. The absorptance α of light of wavelength λ2 (405 nm) in Sm ions is α = 0.035 / mm. In this embodiment, about 75% of light of wavelength λ2 can be absorbed by the core portion 31. On the other hand, Pr ions hardly absorb light having a wavelength of λ1 (445 nm).

  The second optical fiber 20 includes a reflective film 53 at the first end 20a and a reflective film 54 at the second end 20b. The reflection film 53 has a transmittance of 95% or more for light of wavelength λ1 (445 nm), wavelength λ2 (405 nm), and wavelength λ3 (635 nm), and a reflectance of 99.5% or more for light of wavelength λ4 (560 nm). Designed to be The reflective film 54 is designed so that the transmittance with respect to the light with the wavelengths λ1, λ2, and λ3 is 95% or more and the reflectance with respect to the light with the wavelength λ4 is about 95%.

  With this configuration, after the light having the wavelength λ4 is repeatedly reflected between the reflective film 53 and the reflective film 54, laser oscillation is performed, and the second laser light having the wavelength λ4 (560 nm) is generated. In the above configuration, the second excitation light having the wavelength λ2 is not completely absorbed by the core portion 31, and a part of the light is emitted from the second end 30b. Note that the first excitation light having the wavelength λ1, the first laser light having the wavelength λ3, and the second laser light having the wavelength λ4 are also emitted from the second end 30b.

  From the second end 30b of the second optical fiber 30, the laser beams having the wavelengths λ1, λ2, λ3, and λ4 are extracted with an output of about 0.1 to 0.11 W. . At this time, the laser efficiency in the second optical fiber 30 was about 0.3. The coupling efficiency between the first optical fiber 20 and the second optical fiber 30 was about 0.85. Here, the coupling efficiency is a value indicating the proportion of light incident on the core portion 31 of the second optical fiber 30 out of the light emitted from the second end 20b of the first optical fiber 20.

  FIG. 5 is a spectrum diagram of the laser beam obtained by the configuration of the above embodiment. Laser light having peaks at four wavelengths (405 nm, 445 nm, 560 nm, and 635 nm) is obtained. Thereby, according to the fiber laser apparatus 1 of this embodiment, the light of multiple wavelengths can be obtained rather than the kind of wavelength which can be inject | emitted with the excitation light source part 10. FIG.

  Note that the values of the wavelengths λ1 to λ4 described in the above embodiments are merely examples, and the present invention is not limited to these values.

  In the present embodiment, the diameter of the core portion 31 of the second optical fiber 30 is larger than the diameter of the core portion 21 of the first optical fiber 20. This is because the cross-sectional area of the core part 31 of the second optical fiber 30 located in the rear stage is made larger than the cross-sectional area of the core part 21 of the first optical fiber 20 located in the front stage. The light emitted from the second end 20b is intended to efficiently enter the first end 30a of the second optical fiber 30. That is, the cross-sectional area of each core part (21, 31) can transmit light more efficiently by making the cross-sectional area of the core part 31 larger than the cross-sectional area of the core part 21.

  However, when the cross-sectional area of each core part (21, 31) does not have such a relationship, although the output of the laser beam obtained compared with the said Example may fall, by the excitation light source part 10, There is no substitute in that light having multiple wavelengths can be obtained rather than the types of wavelengths that can be emitted. The present invention is within the scope of such a configuration.

[Second Embodiment]
FIG. 6 is a drawing schematically showing the configuration of the fiber laser device of the second embodiment. In addition, about the structure which is common in 1st embodiment, the same code | symbol is attached | subjected and description is simplified or abbreviate | omitted.

  The fiber laser device 1 of the present embodiment further includes a third optical fiber 40 as compared with the first embodiment. The third optical fiber 40 is disposed at a position farther from the excitation light source unit 10 in the direction of the optical axis 2 than the first optical fiber 20 and the second optical fiber 30. Hereinafter, of the end portions of the third optical fiber 40, the end portion on the side close to the second optical fiber 30 in the direction of the optical axis 2 is referred to as “first end 40 a” and is opposite to the first end 40 a. Is called “second end 40b”.

  The third optical fiber 40 includes a core portion 41, a cladding portion 42 made of a material having a lower refractive index than the core portion 41, and a covering portion 43 that is disposed outside the cladding portion 42 and covers the cladding portion 42. . The core portion 41 is doped with a predetermined second dopant (here, Sm). That is, in this embodiment, the dopant doped in the core part 41 of the third optical fiber 40 is the same material as the dopant doped in the core part 31 of the second optical fiber 30.

  The third optical fiber 40 is also inserted into the ferrule 25 formed in a cylindrical shape, and is fixed to the ferrule 25 by the adhesive layer 24. Hereinafter, the second optical fiber 40, the adhesive layer 24, and the ferrule 25 are collectively referred to as a “third optical fiber body 46”.

  A spacer 60 is disposed between the second optical fiber body 36 and the third optical fiber body 46 in the same manner as between the first optical fiber body 26 and the second optical fiber body 36. The arrangement purpose of the spacer 60 is the same as that of the first embodiment, and the description is omitted. The spacer 60 exhibits extremely high translucency with respect to at least light of wavelength λ1, wavelength λ2, wavelength λ3, and wavelength λ4.

  A reflective film 55 is formed on the first end 40a of the third optical fiber 40, and a reflective film 56 is formed on the second end 40b.

  The reflection film 55 has a wavelength λ 1 of the first excitation light emitted from the first excitation light source 11, a wavelength λ 2 of the second excitation light emitted from the second excitation light source 12, and the first wavelength generated by the first optical fiber 20. It has a high transmittance (for example, 90% or more) with respect to light of wavelength λ3 of one laser beam and light of wavelength λ4 of the second laser beam generated by the second optical fiber 30. Further, it has an extremely high reflectance (for example, 99% or more) with respect to a predetermined wavelength λ5. This wavelength λ5 is a wavelength included in the wavelength band of light emitted by exciting Sm.

  The reflective film 56 has a high transmittance (for example, 90% or more) with respect to light having wavelengths λ1, λ2, λ3, and λ4. Further, it has a predetermined reflectance (for example, 95% ± 1%) with respect to the light of wavelength λ5.

  In such a configuration, the reflective film 55 and the reflective film 56 constitute a resonator (corresponding to a “third resonator”) for light having a wavelength λ5. This wavelength λ5 corresponds to the “fifth wavelength”.

  Also in the present embodiment, the wavelength of the first excitation light emitted from the first excitation light source 11 is set to 445 nm and the wavelength of the second excitation light emitted from the second excitation light source 12 is the same as the configuration of the first embodiment. Let λ2 be 405 nm. Further, the wavelength λ3 of the first laser light generated by the first optical fiber 30 is set to 635 nm.

  In the present embodiment, the wavelength λ4 of the second laser light generated by the second optical fiber 40 is 594 nm. That is, the reflection characteristics of the reflection film 53 and the reflection film 54 constituting the second resonator are designed so that light having such a wavelength is oscillated.

  Then, the first excitation light having a wavelength of 445 nm (λ1), the second excitation light having a wavelength of 405 nm (λ2), the first laser light having a wavelength of 635 nm (λ3), and the wavelength 594 nm (λ4) having passed through the second optical fiber 30. The second laser light is incident on the core portion 41 of the third optical fiber 40. As described above with reference to FIG. 4, Sm has a low absorptance with respect to light having a wavelength of around 445 nm (for example, 430 nm to 450 nm) and light having a wavelength of 500 nm or more, and has a wavelength of about 405 nm (for example, wavelength of 395 nm to 415 nm) ) Light absorption rate is high.

  For this reason, in the core part 41 of the third optical fiber 40, the first excitation light having a wavelength of 445 nm, the first laser light having a wavelength of 635 nm, and the second laser light having a wavelength of 594 nm are not absorbed or hardly absorbed, while the first excitation light having a wavelength of 405 nm is absorbed. The double excitation light is absorbed to some extent. And Sm will emit the fluorescence which has a wavelength distribution as shown by the emission spectrum of FIG. 4, if this 2nd excitation light is absorbed.

  Here, since the reflection film 56 has a high transmittance with respect to the light of the wavelength λ1, the wavelength λ2, the wavelength λ3, and the wavelength λ4, the first excitation light that has passed through the core portion 41 of the third optical fiber 40. The first laser light and the second laser light and a part of the second excitation light remaining without being absorbed in the core portion 41 are transmitted through the reflection film 56 and extracted outside the fiber laser device 1. It is. Of the fluorescence emitted from the third optical fiber 40, light of a specific wavelength is reflected by the reflective film 56 without loss. Here, light of wavelength λ5 is reflected by the reflective film 56. At this time, if the wavelength λ5 is the peak wavelength of fluorescence corresponding to the energy transition of electrons, light in a predetermined wavelength band including the wavelength λ5 may be reflected by the reflective film 56.

  Fluorescence having the wavelength λ5 travels toward the first end 40a of the third optical fiber 40 when reflected by the reflective film 56. The reflective film 55 provided on the first end 40a has an extremely high reflectance with respect to light having the wavelength λ5. For this reason, when the fluorescence reaches the reflection film 55, the component of the wavelength λ5 is reflected without loss and proceeds again toward the reflection film 56.

  Thereafter, when reflection is repeated between the reflection film 55 and the reflection film 56 and a predetermined oscillation condition is satisfied, a laser beam having a wavelength λ5 (hereinafter referred to as “third laser beam”) is generated, and this third laser is generated. Light passes through the reflective film 56 and is extracted outside the fiber laser device 1.

  According to the above configuration, only the first excitation light source 11 that emits the light with the wavelength λ1 and the second excitation light source 12 that emits the light with the wavelength λ2 are prepared, and the wavelengths λ1, λ2, λ3, λ4, and λ5 are obtained. A fiber laser device 1 that can extract light of five types of wavelengths is realized. That is, according to the fiber laser device 1, it is possible to realize a laser device that can emit light of more types of wavelengths than the types of wavelengths that the excitation light source unit 10 can emit.

  In the following, portions different from the first embodiment will be described for the configuration of a specific example.

  The configuration of the excitation light source unit 10 is the same as that of the first embodiment. In the present embodiment, the first excitation light having the wavelength λ1 (445 nm) having an output of about 0.65 W and the second excitation light having the output of about 1.1 W having the wavelength λ2 (405 nm) are used as the excitation light source. The light enters the core portion 21 of the first optical fiber 20 from the portion 10.

  The first optical fiber 20, the reflective film 51, and the reflective film 52 are common to the first embodiment. Under this configuration, as an example of the output of light emitted from the second end 20b of the first optical fiber 20, the optical output of the wavelength λ1 is 0.14 W, the optical output of the wavelength λ2 is 1.1 W, and the wavelength λ3 The light output of was 0.14 W. At this time, the laser efficiency (ratio of the obtained laser light energy to the absorbed excitation light energy) in the first optical fiber 20 was about 0.35.

  The second optical fiber 30 is made of a fluoride glass in which the core portion 31 has a diameter of 8 μm and Sm ions are added to the core portion 31. The length of the second fiber 30 in the direction of the optical axis 2 is 18 mm. In the present embodiment, the length of the second optical fiber 30 is shorter than that of the first embodiment, and about 45% of light having a wavelength λ2 is absorbed by the core portion 31.

  The second optical fiber 20 includes a reflective film 53 at the first end 20a and a reflective film 54 at the second end 20b. The reflective film 53 has a transmittance of 95% or more for light of wavelength λ1 (445 nm), wavelength λ2 (405 nm), and wavelength λ3 (635 nm), and a reflectance of 99.5% or more for light of wavelength λ4 (594 nm). Designed to be The reflective film 54 is designed so that the transmittance with respect to the light with the wavelengths λ1, λ2, and λ3 is 95% or more and the reflectance with respect to the light with the wavelength λ4 is about 95%.

  With this configuration, after the light with the wavelength λ4 is repeatedly reflected between the reflective film 53 and the reflective film 54, the laser oscillation is performed to generate the second laser light with the wavelength λ4 (594 nm). In the above configuration, the second excitation light having the wavelength λ2 is not completely absorbed by the core portion 31, and a part of the light is emitted from the second end 30b. Note that the first excitation light having the wavelength λ1, the first laser light having the wavelength λ3, and the second laser light having the wavelength λ4 are also emitted from the second end 30b.

  As an example of the output of light emitted from the second end 30b of the second optical fiber 30 under this configuration, the optical output of the wavelength λ1 is 0.13 W, the optical output of the wavelength λ2 is 0.51 W, and the wavelength λ3. Was 0.13 W, and the light output at wavelength λ4 was 0.13 W. At this time, the laser efficiency in the second optical fiber 30 was about 0.3. The coupling efficiency between the first optical fiber 20 and the second optical fiber 30 was about 0.85.

  The third optical fiber 40 is made of fluoride glass in which the core portion 41 has a diameter of 8 μm, and Sm ions are added to the core portion 41. The length of the third fiber 40 in the direction of the optical axis 2 is 50 mm. The absorptance α of light of wavelength λ2 (405 nm) in Sm ions is α = 0.035 / mm. In this embodiment, about 75% of light of wavelength λ2 can be absorbed by the core portion 31.

  The third optical fiber 40 includes a reflective film 55 at the first end 40a and a reflective film 56 at the second end 40b. The reflection film 55 has a transmittance of 95% or more for light of wavelength λ1 (445 nm), wavelength λ2 (405 nm), wavelength λ3 (635 nm), and wavelength λ4 (594 nm), and reflection of light of wavelength λ5 (560 nm). The rate is designed to be 99.5% or higher. The reflective film 56 is designed so that the transmittance with respect to the light with the wavelengths λ1, λ2, λ3, and λ4 is 95% or more and the reflectance with respect to the light with the wavelength λ5 is about 95%. .

  With such a configuration, after the light with the wavelength λ5 is repeatedly reflected between the reflective film 55 and the reflective film 56, laser oscillation is performed to generate the third laser light with the wavelength λ5 (560 nm). In the above configuration, the second excitation light having the wavelength λ2 is not completely absorbed by the core portion 41, and a part of the light is emitted from the second end 40b. Note that the first excitation light having the wavelength λ1, the first laser light having the wavelength λ3, the second laser light having the wavelength λ4, and the third laser light having the wavelength λ5 are also emitted from the second end 40b.

  From the second end 40b of the third optical fiber 40, each of the laser beams of wavelength λ1, wavelength λ2, wavelength λ3, wavelength λ4, and wavelength λ5 is extracted with an output of about 0.1 W. At this time, the laser efficiency in the third optical fiber 40 was about 0.3. The coupling efficiency between the second optical fiber 30 and the third optical fiber 40 was about 0.8.

  In the present embodiment, the dopant doped in the core portion 41 of the third optical fiber 40, the first dopant doped in the core portion 21 of the first optical fiber 20, and the core portion 31 of the second optical fiber 30. It does not matter even if it is a substance different from the second dopant doped in.

  In the present embodiment, the configuration in which three optical fibers (20, 30, 40) are connected in series has been described. However, a configuration in which four or more optical fibers are connected in series may be employed. Is possible.

[Third embodiment]
FIG. 7 is a drawing schematically showing the configuration of the fiber laser device of the third embodiment. In addition, about the structure which is common in 1st embodiment, the same code | symbol is attached | subjected and description is simplified or abbreviate | omitted.

  The fiber laser device 1 of the present embodiment is different from the first embodiment in that the reflective film 53 provided on the first end 30a side of the second optical fiber 30 is omitted. That is, the fiber laser device 1 of this embodiment is configured to include the reflective film 51, the reflective film 52, and the reflective film 54. Other parts are common to the first embodiment.

  That is, in the present embodiment, the reflective film 51 is formed on the first end 20a of the first optical fiber 20, and the reflective film 52 is formed on the second end 20b. And the reflective film is not formed in the 1st end 30a of the 2nd optical fiber 30, The reflective film 54 is formed in the 2nd end 30b.

  The reflective film 51 has a high transmittance (for example, 90% or more) with respect to the wavelength λ1 of the first excitation light emitted from the first excitation light source 11 and the wavelength λ2 of the second excitation light emitted from the second excitation light source 12. )have. Moreover, it has a very high reflectance (for example, 99% or more) with respect to the wavelength λ3 of the first laser beam and the wavelength λ4 of the second laser beam. The wavelength λ3 is a wavelength included in the wavelength band of light emitted when Pr is excited, and the wavelength λ4 is a wavelength included in the wavelength band of light emitted when Sm is excited.

  The reflective film 52 has a high transmittance (for example, 90% or more) with respect to the wavelength λ1 of the first excitation light, the wavelength λ2 of the second excitation light, and the wavelength λ4 of the second laser light. Further, it has a predetermined reflectance (for example, 95% ± 1%) with respect to the wavelength λ3 of the first laser light.

  The reflective film 54 has a transmittance (for example, 90% or more) with respect to light having wavelengths λ1, λ2, and λ3. Further, it has a predetermined reflectance (for example, 95% ± 1%) with respect to light of wavelength λ4.

  Also in the present embodiment, the first excitation light having a wavelength of 445 nm (λ1) and the second excitation light having a wavelength of 405 nm (λ2) that have passed through the first optical fiber 20 and the wavelength 635 nm (λ3) generated by the first optical fiber 20 are used. ) Is incident on the core portion 31 of the second optical fiber 30. In the core part 31 of the second optical fiber 30, the first excitation light with a wavelength of 445 nm and the first laser light with a wavelength of 635 nm are not or hardly absorbed, while the second excitation light with a wavelength of 405 nm is absorbed to some extent.

  Here, since the reflective film 54 has a high transmittance with respect to the light of the wavelength λ1, the wavelength λ2, and the wavelength λ3, the first excitation light and the first light that have passed through the core portion 31 of the second optical fiber 30 are used. One laser beam and a part of the second excitation light remaining without being absorbed in the core portion 31 are transmitted through the reflection film 54 and extracted outside the fiber laser device 1. Of the fluorescence emitted from the second optical fiber 30, light having a specific wavelength is selectively reflected by the reflective film 54. Here, light of wavelength λ4 is reflected by the reflective film 54. At this time, if the wavelength λ4 is the peak wavelength of fluorescence corresponding to the energy transition of electrons, light in a predetermined wavelength band including the wavelength λ4 may be reflected by the reflective film 54.

  Fluorescence having the wavelength λ4 travels toward the first end 30a of the second optical fiber 30 when reflected by the reflective film 54. Since the first end 30 a is not provided with a reflective film, the fluorescence passes through the spacer 60 and enters the second end 20 b of the first optical fiber 20. The reflective film 52 provided at the second end 20b of the first optical fiber 20 has a high transmittance with respect to light having the wavelength λ4. Therefore, the fluorescence having the wavelength λ4 travels through the reflective film 52 and travels in the first optical fiber 20 toward the first end 20a.

  The reflective film 51 provided on the first end 20a of the first optical fiber 20 has an extremely high reflectance with respect to light having a wavelength λ4. For this reason, when the fluorescence reaches the reflection film 51, the component of the wavelength λ4 is reflected without loss and proceeds toward the reflection film 52 again. Then, the light passes through the reflective film 52 and enters the second optical fiber 30, and is reflected again by the reflective film 54 provided at the second end 30 b of the second optical fiber 30.

  Hereinafter, reflection is repeated between the reflective film 51 provided on the first end 20a of the first optical fiber 20 and the reflective film 54 provided on the second end 30b of the second optical fiber 30, and predetermined oscillation conditions are satisfied. When established, a second laser beam having a wavelength λ4 is generated, and the second laser beam passes through the reflection film 54 and is extracted to the outside of the fiber laser device 1.

  In such a configuration, the reflective film 51 and the reflective film 52 constitute a resonator (first resonator) for the light of the third wavelength λ3, and the reflective film 51 and the reflective film 54 constitute a resonator for the light of the fourth wavelength λ4. (Second resonator) is configured. According to this embodiment, since it can be set as the structure which is not provided with the reflecting film 53, the number of the optical members which comprise a reflective surface can be suppressed, and simplification of a manufacturing process and reduction of manufacturing cost are achieved. It is done.

  In the present embodiment, the reflective film 51 is required to have high reflection characteristics with respect to light having wavelengths λ3 and λ4. At this time, the reflective film 51 may be formed so as to exhibit a high reflectance with respect to a wide wavelength band including the wavelengths λ3 and λ4. However, even in this case, it is required to design the wavelengths λ1 and λ2 so as to exhibit high transmittance.

  In the configuration of the second embodiment, a part of the reflection film may be omitted as in the present embodiment, so that the reflection film may be shared by different resonators.

  In the present embodiment, the reflective film 53 is not provided, and the reflective film 51 is shared by the first resonator and the second resonator. On the other hand, the reflective film 53 may be used instead of the reflective film 52, and the reflective film 53 may be shared by the first resonator and the second resonator. That is, the first resonator may be configured by the reflective film 51 and the reflective film 53, and the second resonator may be configured by the reflective film 53 and the reflective film 54.

  Similarly, the reflective film 52 may be shared by the first resonator and the second resonator without having the reflective film 53. In other words, the reflective film 51 and the reflective film 52 may constitute a first resonator, and the reflective film 52 and the reflective film 54 may constitute a second resonator.

1: Fiber laser device of the present invention
2: Optical axis 10: Excitation light source unit 11: First excitation light source 12: Second excitation light source 13, 14, 15: Coupling optical system 16: Dichroic mirror 20: First optical fiber 20a: First end of the first optical fiber 20b: Second end of first optical fiber 21: Core portion of first optical fiber 22: Clad portion of first optical fiber 23: Cover portion of first optical fiber 24: Adhesive layer 25: Ferrule 26: First optical fiber Body 30: Second optical fiber 30a: First end of second optical fiber 30b: Second end of second optical fiber 31: Core portion of second optical fiber 32: Clad portion of second optical fiber 33: Second light Fiber coating portion 36: second optical fiber body 40: third optical fiber 40a: first end of third optical fiber 40b: second end of third optical fiber 41: third light Fiber core portion 42: cladding portion of third optical fiber 43: covering portion of third optical fiber 46: third optical fiber body 51, 52, 53, 54, 55, 56: reflection film 60: spacer 62: holding member 63: Groove

Claims (7)

An excitation light source unit that emits first excitation light of a first wavelength and second excitation light of a second wavelength;
A first optical fiber having a core portion doped with a first dopant;
The second optical fiber is disposed at a position farther in the optical axis direction from the excitation light source part than the first optical fiber, and the core part is doped with a second dopant,
When the first excitation light and the second excitation light are incident, the first optical fiber absorbs a part of the first excitation light to excite the first dopant, Generating laser light and emitting the first excitation light, the second excitation light, and the first laser light;
The second optical fiber absorbs a part of the second excitation light when the first excitation light, the second excitation light, and the first laser light emitted from the first optical fiber are incident. Then, the second dopant is excited to generate a second laser light having a fourth wavelength, and the first excitation light, the second excitation light, the first laser light, and the second laser light are emitted. A fiber laser device.   The fiber laser device according to claim 1, wherein the first dopant is composed of Pr, and the second dopant is composed of Sm.   The said 2nd dopant is not excited by the light of said 1st wavelength, the said 3rd wavelength, or the said 4th wavelength, It is excited by the light of the said 2nd wavelength, The Claim 2 characterized by the above-mentioned. Fiber laser device. A spacer that transmits light of the first wavelength, the second wavelength, the third wavelength, and the fourth wavelength;
The fiber laser device according to claim 1, wherein the first optical fiber and the second optical fiber are connected via the spacer. A first end that is an end of the first optical fiber on the excitation light source side, and a second end opposite to the first end of the first optical fiber, or the first light of the second optical fiber. A first resonator provided at a first end which is an end portion on a fiber side;
A second resonator provided at the second end of the first optical fiber or the first end of the second optical fiber and a second end opposite to the first end of the second optical fiber. And
The first resonator resonates the light of the third wavelength to generate the first laser light, and transmits the light of the first wavelength and the light of the second wavelength,
The second resonator resonates the fourth wavelength light to generate the first laser light, and transmits the first wavelength light, the second wavelength light, and the third wavelength light. The fiber laser device according to any one of claims 1 to 4, wherein the fiber laser device is provided. A first end that is an end of the first optical fiber on the excitation light source side, and a second end opposite to the first end of the first optical fiber, or the first light of the second optical fiber. A first resonator provided at a first end which is an end portion on a fiber side;
A second resonator provided at the first end of the first optical fiber and an end of the second optical fiber opposite to the end of the first optical fiber;
The first resonator resonates the light of the third wavelength to generate the first laser light, and transmits the light of the first wavelength and the light of the second wavelength,
The second resonator resonates the fourth wavelength light to generate the first laser light, and transmits the first wavelength light, the second wavelength light, and the third wavelength light. And
5. The fiber laser device according to claim 1, wherein the first resonator and the second resonator are shared by the first end of the first optical fiber. . A third optical fiber disposed at a position farther in the optical axis direction from the excitation light source part than the second optical fiber, and further comprising a third optical fiber doped with the second dopant in the core part;
When the first excitation light, the second excitation light, the first laser light, and the second laser light emitted from the second optical fiber are incident, the third optical fiber receives the second excitation light. And absorbing the first dopant to excite the second dopant to generate a third laser beam having a fifth wavelength, and the first excitation light, the second excitation light, the first laser light, and the second laser. The fiber laser apparatus according to claim 1, wherein the light and the third laser light are emitted.