JP2015170795A - Fiber laser equipment - Google Patents

Abstract

A fiber laser device capable of selectively oscillating laser light having a wavelength of 616 nm or the vicinity thereof with high intensity is provided.
An optical fiber having a core containing praseodymium ions as a luminescent substance that emits fluorescence, an incident side mirror disposed on one end surface of the optical fiber, and an output side mirror disposed on the other end surface of the optical fiber And a laser beam is oscillated from the exit-side mirror by causing the excitation light to enter the one end face of the optical fiber via the entrance-side mirror. The entrance-side mirror and the exit-side mirror are made of a dielectric multilayer film. Thus, at any wavelength in the wavelength region of 616 nm ± 3 nm, the reflectance of the output side mirror is 95% ± 1%, and at the wavelength of 605 nm, the reflectivity of the incident side mirror and the output side mirror is 97% or more and 635 nm. In terms of wavelength, the reflectance of the incident side mirror is 99% or more and the reflectance of the exit side mirror is 97% or more. It is a sign.
[Selection] Figure 1

Description

  The present invention relates to a fiber laser device in which resonators are arranged on both end faces of an optical fiber.

In a spectral 3D cinema projector, two types of light sources having wavelengths different from each other by 15 nm or more are required as light sources of red, green, and blue colors. As a light source used for such a 3D cinema projector, it is planned to adopt a laser light source from the viewpoint of color reproducibility and lifetime characteristics.
In this 3D cinema projector, a laser diode having an oscillation wavelength of 640 nm is employed as one of the two types of red laser light sources because a high output can be obtained. Therefore, the other red laser light source is required to oscillate laser light having a wavelength of 625 nm (640 nm-15 nm) or less or a wavelength of 655 nm (640 nm + 15 nm) or more. However, at present, it is difficult to obtain a high-power laser diode having an oscillation wavelength of 625 nm. Therefore, the use of a laser diode having an oscillation wavelength of 655 nm as the other red laser light source has been studied.
However, the visibility (0.0816) of light with a wavelength of 655 nm is very low compared to the visibility (0.4656) of light with a wavelength of 613 nm, for example. Therefore, when a laser diode with an oscillation wavelength of 655 nm is used as the other red laser light source, there is a problem that a large amount of energy is required to ensure sufficient brightness.

  By the way, as a laser light source other than the laser diode, there is known a fiber laser device that excites an optical fiber having a core doped with rare earth element ions in fluoride glass by a laser diode (Patent Documents 1 to 4). reference.).

FIG. 14 is a diagram showing a fluorescence spectrum of a material in which praseodymium ions (Pr ³⁺ ) are doped in fluoride glass containing aluminum fluoride as a main component. As shown in this figure, in a material doped with praseodymium ions (Pr ³⁺ ), a fluorescence spectrum having peaks at a wavelength of 605 nm and a wavelength of 635 nm is obtained. Therefore, when praseodymium ions are used as the rare earth element ions doped into the optical fiber, it is possible to obtain a fiber laser device having an oscillation wavelength of 605 nm or 635 nm.

However, since the other red laser light source in the 3D cinema projector needs to have an oscillation wavelength of 625 nm, a fiber laser device having an oscillation wavelength of 635 nm cannot be used.
Further, in the DCI (Digital Cinema Initiatives) standard, the color reproduction limit value of red light is 613 nm. For this reason, a fiber laser device having an oscillation wavelength of 605 nm cannot be used as the other red laser light source in the 3D cinema projector.
Thus, a fiber laser device that oscillates laser light with a wavelength of 613 to 625 nm that can be used as the other red laser light source in a 3D cinema projector has not been commercialized, and development of the product is desired.

Japanese Patent Application Laid-Open No. 11-017266 Japanese Patent Laid-Open No. 11-204862 JP 2010-080927 A Japanese Patent Laid-Open No. 04-127591

  An object of the present invention is to provide a fiber laser device capable of selectively oscillating laser light having a wavelength of 616 nm or its vicinity with high intensity.

The fiber laser device of the present invention includes an optical fiber having a core containing praseodymium ions as a light emitting substance that emits fluorescence, an incident side mirror disposed on one end surface of the optical fiber, and an output side disposed on the other end surface of the optical fiber. A fiber laser device that oscillates laser light from the exit-side mirror by making excitation light incident on one end surface of the optical fiber via the entrance-side mirror.
Each of the incident side mirror and the emission side mirror is constituted by a dielectric multilayer film,
In any wavelength in the wavelength region of 616 nm ± 3 nm, the reflectance of the exit side mirror is 95% ± 1%,
At a wavelength of 605 nm, the reflectance of the incident side mirror is 99% or more, and the reflectance of the emission side mirror is 97% or more,
At a wavelength of 635 nm, the reflectance of the incident side mirror is 99% or more, and the reflectance of the exit side mirror is 97% or more.

Further, the fiber laser device of the present invention is an optical fiber having a core containing praseodymium ions as a light emitting substance that emits fluorescence, an incident side mirror disposed on one end surface of the optical fiber, and an other end surface of the optical fiber. A fiber laser device that oscillates laser light from the exit-side mirror by entering excitation light into one end surface of the optical fiber via the entrance-side mirror.
Each of the incident side mirror and the emission side mirror is constituted by a dielectric multilayer film,
In any wavelength in the wavelength region of 616 nm ± 3 nm, the reflectance of the exit side mirror is 95% ± 1%,
At a wavelength of 605 nm, the reflectance of the incident side mirror or the reflectance of the output side mirror is 90% or less,
At a wavelength of 635 nm, the reflectance of the incident side mirror is 99% or more, and the reflectance of the exit side mirror is 97% or more.

Further, the fiber laser device of the present invention is an optical fiber having a core containing praseodymium ions as a light emitting substance that emits fluorescence, an incident side mirror disposed on one end surface of the optical fiber, and an other end surface of the optical fiber. A fiber laser device that oscillates laser light from the exit-side mirror by entering excitation light into one end surface of the optical fiber via the entrance-side mirror.
Each of the incident side mirror and the emission side mirror is constituted by a dielectric multilayer film,
In any wavelength in the wavelength region of 616 nm ± 3 nm, the reflectance of the exit side mirror is 95% ± 1%,
At a wavelength of 605 nm, the reflectance of the incident side mirror or the reflectance of the output side mirror is 90% or less,
The reflectance of the incident side mirror or the reflectance of the exit side mirror is 90% or less at a wavelength of 635 nm.

Further, the fiber laser device of the present invention is an optical fiber having a core containing praseodymium ions as a light emitting substance that emits fluorescence, an incident side mirror disposed on one end surface of the optical fiber, and an other end surface of the optical fiber. A fiber laser device that oscillates laser light from the exit-side mirror by entering excitation light into one end surface of the optical fiber via the entrance-side mirror.
Each of the incident side mirror and the emission side mirror is constituted by a dielectric multilayer film,
In any wavelength in the wavelength region of 616 nm ± 3 nm, the reflectance of the exit side mirror is 95% ± 1%,
At a wavelength of 605 nm, the reflectance of the incident side mirror is 99% or more, and the reflectance of the emission side mirror is 97% or more,
The reflectance of the incident side mirror is 90% or less at a wavelength of 635 nm.
In the fiber laser device of the present invention having this configuration, the reflectance of the output side mirror is preferably 90% or less at a wavelength of 635 nm.

  According to the fiber laser device of the present invention, since the exit side mirror constituting the resonator, or both the entrance side mirror and the exit side mirror have specific spectral reflectance characteristics, a laser beam having a wavelength of 616 nm or in the vicinity thereof. Can be selectively oscillated with high intensity.

It is sectional drawing for description which shows the structure in an example of the fiber laser apparatus of this invention. It is a spectral reflectance curve figure in an example of the incident side mirror. It is a spectral reflectance curve figure in the other example of the incident side mirror. It is the elements on larger scale of the spectral reflectance curve shown in FIG. It is a spectral reflectivity curve figure in one example of an output side mirror. It is the elements on larger scale of the spectral reflectance curve shown in FIG. It is a spectral reflectance curve figure in the other example of the output side mirror. It is the elements on larger scale of the spectral reflectance curve shown in FIG. 6 is a spectral reflectance curve diagram of an output side mirror in Comparative Example 1. FIG. It is the elements on larger scale of the spectral reflectance curve shown in FIG. FIG. 3 is a diagram illustrating a spectrum of laser light oscillated from the fiber laser device according to the first embodiment. 6 is a diagram illustrating a spectral spectrum of laser light oscillated from a fiber laser device according to Example 2. FIG. It is a figure which shows the spectrum of the laser beam oscillated from the fiber laser apparatus concerning the comparative example 1. It is a figure which shows the fluorescence spectrum of the material which doped the praseodymium ion (Pr ^<3+> ) in the fluoride glass which has aluminum fluoride as a main component.

Hereinafter, embodiments of the fiber laser device of the present invention will be described.
[Configuration of fiber laser device]
FIG. 1 is a cross-sectional view illustrating the configuration of an example of the fiber laser device of the present invention. This fiber laser device includes an optical fiber 10 that emits fluorescence upon receiving excitation light, a resonator 20 that resonates fluorescence generated in the optical fiber 10, and an excitation laser element 30 that emits excitation light incident on the optical fiber 10. And a coupling lens unit 35 for coupling the optical fiber 10 and the excitation laser element 30.

[Optical fiber]
The optical fiber 10 includes a linear core 15 having a circular cross section serving as a laser medium, and a cylindrical clad 16 integrally provided so as to cover the outer peripheral surface of the core 15. The optical fiber 10 is inserted into a cylindrical fiber tube 17 made of, for example, zirconia. The clad 16 and the fiber tube 17 in the optical fiber 10 are bonded by, for example, a heat resistant adhesive.
Further, both end surfaces of the optical fiber 10 are mirror-finished with an accuracy of 1 / 5λ with respect to the wavelength λ of the oscillation wavelength (for example, 616 nm). Thereby, one end surface (left end surface in the figure) of the optical fiber 10 is an incident side end surface 11 on which excitation light is incident, and the other end surface of the optical fiber 10 is an emission side end surface 12 from which laser light is emitted. .

As a material constituting the core 15 in the optical fiber 10, a material in which praseodymium ions (Pr ³⁺ ) are contained in a base material as a light emitting substance that emits fluorescence upon receiving excitation light is used.
As a base material of the core 15, fluoride glass mainly composed of aluminum fluoride such as AlF ₃ —BaF ₂ —SrF ₂ —CaF ₂ —MgF ₂ —YF ₃ , ZBLANP (ZrF ₄ —BaF ₂ —LaF ₃ —AlF). Zr fluoride glass such as ₃ -NaF-PbF ₂ ) can be used.
The ratio of praseodymium ions in the core 15 is, for example, 500 to 6000 ppm.

  As a material constituting the clad 16 in the optical fiber 10, Al-based fluoride glass, Zr-based fluoride glass, or the like can be used.

The total length of the optical fiber 10 is, for example, 30 to 100 mm.
Moreover, the outer diameter of the core 15 in the optical fiber 10 is, for example, 7 to 40 μm.

[Resonator]
The resonator 20 includes an incident side mirror 21 disposed on the incident side end surface 11 of the optical fiber 10 and an output side mirror 22 disposed on the output side end surface 12 of the optical fiber 10.

Each of the entrance side mirror 21 and the exit side mirror 22 in the resonator 20 is a dielectric multilayer film in which low refractive index layers made of, for example, SiO ₂ and high refractive index layers made of, for example, Ta ₂ O ₅ are alternately laminated. It is comprised by. The thickness of the dielectric multilayer film constituting the incident side mirror 21 and the emission side mirror 22 is preferably 2 to 5 μm. When this thickness is too small, it is difficult to realize a desired spectral reflectance characteristic. On the other hand, when the thickness is excessive, light (loss) that does not return into the core 15 when light having an angle with respect to the fiber axis is reflected by the incident side mirror 21 or the output side mirror 22. The laser efficiency becomes worse.
The number of low refractive index layers and high refractive index layers in the dielectric multilayer film constituting the incident side mirror 21 is 10 to 25 layers (20 to 50 layers in total).
Moreover, the number of layers of the low refractive index layer and the high refractive index layer in the dielectric multilayer film constituting the exit side mirror 22 is 10 to 25 layers (20 to 50 layers in total), respectively.

As the incident side mirror 21, a mirror having a high transmittance of excitation light from the excitation laser element 30 and a high reflectance of light in the wavelength region of the oscillated laser light is used.
As the output side mirror 22, a mirror having a spectral reflectance characteristic in which the reflectance is 95% ± 1% at any wavelength in the wavelength region of 616 nm ± 3 nm is used. When the reflectance of light in the wavelength region of 616 nm ± 3 nm in the emission side mirror 22 is excessively small, the energy stored in the core 15 is not sufficient, so that the threshold value of the incident energy of the excitation light (laser oscillation threshold value) Becomes larger and the efficiency becomes worse. On the other hand, when the reflectance of light in the wavelength region of 616 nm ± 3 nm in the emission side mirror 22 is excessive, the extraction output decreases due to slight absorption or diffusion in the core 15. Experimentally, 95% has been found to be optimal.

The resonator 20 satisfies any of the following conditions (1) to (5).
Condition (1):
At the wavelength of 605 nm, the reflectance of the incident side mirror 21 is 99% or more, the reflectance of the output side mirror 22 is 97% or more, and at the wavelength of 635 nm, the reflectance of the incident side mirror 21 is 99%. %, And the reflectance of the exit side mirror 22 is 97% or more.
Condition (2):
At the wavelength of 605 nm, the reflectivity of the incident side mirror 21 or the reflectivity of the output side mirror 22 is 90% or less, and at the wavelength of 635 nm, the reflectivity of the incident side mirror 21 is 99% or more and The reflectance of the side mirror 22 is 97% or more.
Condition (3):
At the wavelength of 605 nm, the reflectance of the incident side mirror 21 or the reflectance of the output side mirror 22 is 90% or less, and at the wavelength of 635 nm, the reflectance of the incident side mirror 21 or the reflectance 22 of the output side mirror 22 is 90% or less.
Condition (4):
At the wavelength of 605 nm, the reflectance of the incident side mirror 21 is 99% or more, the reflectance of the output side mirror 22 is 97% or more, and at the wavelength of 635 nm, the reflectance of the incident side mirror 21 is 90%. % Or less.
Condition (5):
In condition (4), the reflectance of the exit side mirror 22 is 90% or less at a wavelength of 635 nm. That is, at the wavelength of 605 nm, the reflectance of the incident side mirror is 99% or more, and the reflectance of the emission side mirror is 97% or more. At the wavelength of 635 nm, the reflectance of the incident side mirror and the emission side The reflectivity of the mirror is 90% or less.

By satisfying any of the above conditions (1) to (5), it is possible to prevent at least one of the laser beam having a wavelength of 605 nm or its vicinity and the laser beam having a wavelength of 635 nm or its vicinity from oscillating.
More specifically, when the reflectance of the incident side mirror 21 or the reflectance of the output side mirror 22 is 90% or less at a wavelength of 605 nm, light having a wavelength of 605 nm or its vicinity has a large absorption loss. Therefore, it is possible to prevent the laser-oscillated light from being emitted from the exit side mirror 22.
Similarly, when the reflectance of the incident side mirror 21 or the reflectance of the emission side mirror 22 is 90% or less at a wavelength of 635 nm, light having a wavelength of 635 nm or its vicinity is present in the core 15 of the optical fiber 10. Laser oscillation can be prevented.
Further, at the wavelength of 605 nm, the reflectivity of the incident side mirror 21 is 99% or more and the reflectivity of the output side mirror 22 is 97% or more, in the core 15 of the optical fiber 10, Since light having a wavelength of 605 nm or in the vicinity thereof is not sufficiently amplified and is not in an inversion distribution state, laser oscillation can be prevented.
Similarly, at the wavelength of 635 nm, the reflectivity of the incident side mirror 21 is 99% or more and the reflectivity of the output side mirror 22 is 97% or more. In addition, it is possible to prevent light having a wavelength of 635 nm or its vicinity from lasing.

  If none of the above conditions (1) to (5) is satisfied, there is a possibility that a laser beam having a wavelength of 605 nm or its vicinity or a laser beam having a wavelength of 635 nm or its vicinity may be oscillated.

  It is possible to limit the oscillation wavelength by using a narrow band mirror having a half width of about 10 nm for the incident side mirror 21 or the output side mirror 22, but the number of dielectric multilayer films is 80 layers (8 μm) or more. When such a mirror is used, the efficiency of the laser is extremely deteriorated as described above.

An example of the incident side mirror 21 is composed of a dielectric multilayer film in which 23 layers of low refractive index layers made of SiO ₂ and 23 layers of high refractive index layers made of Ta ₂ O ₅ are alternately laminated. The total thickness of the low refractive index layers is 1.6 μm, and the total thickness of the high refractive index layers is 2.3 μm. A spectral reflectance curve diagram of the incident side mirror 21 of this example is shown in FIG. The incident side mirror 21 has a light reflectance of 99% or more in a wavelength range of 570 to 640 nm and a light transmittance of 95% or more in a wavelength of 430 to 480 nm.

As another example of the incident side mirror 21, it is constituted by a dielectric multilayer film in which 25 low refractive index layers made of SiO ₂ and 25 high refractive index layers made of Ta ₂ O ₅ are alternately laminated. The total thickness of the low refractive index layers is 1.6 μm, and the total thickness of the high refractive index layers is 2.6 μm. FIG. 3 shows a spectral reflectance curve of the incident side mirror 21 of this example, and FIG. 4 shows a partially enlarged view of the spectral reflectance curve shown in FIG. The incident side mirror has a light transmittance of 430 to 480 nm and a light transmittance of 95% or more, a light reflectance of 560 to 620 nm and a light reflectance of 635 nm of 90% or less.

An example of the exit side mirror 22 is composed of a dielectric multilayer film in which 27 layers of low refractive index layers made of SiO ₂ and 27 layers of high refractive index layers made of Ta ₂ O ₅ are alternately laminated, The total thickness of the low refractive index layers is 2.4 μm, and the total thickness of the high refractive index layers is 2.3 μm. FIG. 5 shows a spectral reflectance curve of the output side mirror 22 of this example, and FIG. 6 shows a partially enlarged view of the spectral reflectance curve shown in FIG. The exit side mirror 22 has a reflectance of 95% for light with a wavelength of 616 nm, 99.2% for light with a wavelength of 605 nm, and 99.8% for light with a wavelength of 635 nm.

To give another example of the output side mirror 22, it is constituted by a dielectric multilayer film in which 21 layers of a low refractive index layer made of SiO ₂ and 21 layers of a high refractive index layer made of Ta ₂ O ₅ are alternately laminated. The total thickness of the low refractive index layers is 2.2 μm, and the total thickness of the high refractive index layers is 1.6 μm. FIG. 7 shows a spectral reflectance curve of the output side mirror 22 of this example, and FIG. 8 shows a partially enlarged view of the spectral reflectance curve shown in FIG. The exit side mirror 22 has a reflectivity of 95.2% for light having a wavelength of 619 nm, 81% for light having a wavelength of 605 nm, and 92.2% for light having a wavelength of 635 nm.

[Excitation laser element and coupling lens unit]
The excitation laser element 30 is disposed so as to face the incident side mirror 21 in the resonator 20 via the coupling lens unit 35 (see FIG. 1).
As the excitation laser element 30, one that emits light having a wavelength capable of exciting praseodymium ions in the core 15 of the optical fiber 10, for example, blue light having a wavelength range of 430 to 480 nm is used. A specific example of such an excitation laser element 30 is a GaN-based laser diode.
The coupling lens unit 35 is configured such that two lenses 36 and 37 are arranged along the optical path of the excitation light emitted from the excitation laser element 30.

  According to the fiber laser device of the present invention, since the exit side mirror 22 constituting the resonator 20 or both the entrance side mirror 21 and the exit side mirror 22 have specific spectral reflectance characteristics, the wavelength 616 nm or The nearby laser beam can be selectively oscillated with high intensity.

<Example 1>
In accordance with the configuration shown in FIG. 1, a fiber laser device having the following specifications was produced. This fiber laser device was operated, and the spectrum of the oscillated laser beam was measured with a spectrometer having a resolution of about 1 nm. The results are shown in FIG.

[Optical fiber]
Total length of optical fiber: 40mm
Core material: Fluoride glass composed mainly of aluminum fluoride, doped with 3000 ppm praseodymium ions Core outer diameter: 15 μm
[Resonator]
Configuration of incident side mirror: low refractive index layer (number of layers = 23, total thickness = 1.6 μm) made of SiO ₂ (refractive index by light of wavelength 500 nm = 1.46) and Ta ₂ O ₅ (wavelength of 500 nm) Dielectric multilayer film (overall thickness = 3.9 μm) in which high refractive index layers (number of layers = 23, total thickness = 2.3 μm) made of light refractive index = 2.03) are alternately laminated. Consists of.
Spectral reflectance characteristics of the incident side mirror: As shown in FIG. 2 (transmittance of light with a wavelength of 430 to 480 nm> 95%, reflectivity of light with a wavelength of 570 to 640 nm> 99%).
Configuration of output side mirror: low refractive index layer made of SiO ₂ (number of layers = 27, total thickness = 2.4 μm) and high refractive index layer made of Ta ₂ O ₅ (number of layers = 27, total thickness = 2) .3 μm) and a dielectric multilayer film (overall thickness = 4.7 μm).
Spectral reflectance characteristics of the exit side mirror: As shown in FIGS. 5 and 6 (the reflectance of light having a wavelength of 616 nm is 95%, the reflectance of light having a wavelength of 605 nm is 99.2%, and the reflectance of light having a wavelength of 635 nm is 99.8%).
This resonator satisfies the condition (1).
[Excitation laser element]
A GaN-based laser diode (excitation light peak wavelength = 445 nm) was used.

<Example 2>
A fiber laser device having the same configuration as that of Example 1 was manufactured except that the resonator mirror was changed to one having the following specifications. The fiber laser device was operated, and the spectrum of the oscillated laser beam was measured. The results are shown in FIG.

[Resonator]
Structure of incident side mirror: low refractive index layer made of SiO ₂ (number of layers = 25, total thickness = 1.6 μm) and high refractive index layer made of Ta ₂ O ₅ (number of layers = 25, total thickness = 2) .6 μm) and a dielectric multilayer film (overall thickness = 4.2 μm).
Spectral reflectance characteristics of incident side mirror: as shown in FIG. 3 and FIG. 4 (transmittance of light of wavelength 430 to 480 nm> 95%, reflectivity of light of wavelength 560 to 620 nm> 99%, reflection of light of wavelength 635 nm Rate <90%).
Configuration of exit side mirror: low refractive index layer made of SiO ₂ (number of layers = 21, total thickness = 2.2 μm) and high refractive index layer made of Ta ₂ O ₅ (number of layers = 21, total thickness = 1) .6 μm) and a dielectric multilayer film (overall thickness = 3.8 μm).
Spectral reflectance characteristics of the output side mirror: as shown in FIGS. 7 and 8 (reflectance of light having a wavelength of 619 nm = 95.2%, reflectance of light having a wavelength of 605 nm = 81%, reflectance of light having a wavelength of 635 nm = 89.9%).
This resonator satisfies the condition (3).

<Comparative example 1>
A fiber laser device having the same configuration as that of Example 1 was manufactured except that the emission side mirror was changed to one having the following specifications. The fiber laser device was operated, and the spectrum of the oscillated laser beam was measured. The results are shown in FIG.
Configuration of exit side mirror: low refractive index layer made of SiO ₂ (number of layers = 10, total thickness = 1.5 μm) and high refractive index layer made of Ta ₂ O ₅ (number of layers = 9, total thickness = 0) .5 μm) and a dielectric multilayer film (overall thickness = 2.0 μm).
Spectral reflectance characteristics of the exit side mirror: As shown in FIGS. 9 and 10 (the reflectance of light having a wavelength of 616 nm is 95%, the reflectance of light having a wavelength of 605 nm is 95.3%, and the reflectance of light having a wavelength of 635 nm is 92%).

From the results shown in FIGS. 11 and 12, it was confirmed that the fiber laser device according to Example 1 and Example 2 can selectively oscillate laser light having a wavelength of 616 nm or its vicinity with high intensity. .
Therefore, as in the fiber laser devices according to the first and second embodiments, by controlling the spectral reflectance of the output side mirror that constitutes the resonator, or the spectral reflectance of both the output side mirror and the incident side mirror. It was confirmed that laser light having a wavelength of 616 nm or its vicinity can be selectively oscillated with high intensity.

DESCRIPTION OF SYMBOLS 10 Optical fiber 11 Incident side end surface 12 Outgoing side end surface 15 Core 16 Cladding 17 Fiber tube 20 Resonator 21 Incident side mirror 22 Outgoing side mirror 30 Excitation laser element 35 Coupling lens units 36 and 37 Lens

Claims (5)

An optical fiber having a core containing praseodymium ions as a luminescent substance that emits fluorescence, and a resonator composed of an incident side mirror disposed on one end face of the optical fiber and an output side mirror disposed on the other end face of the optical fiber In the fiber laser device that oscillates the laser light from the exit side mirror by making the excitation light incident on one end surface of the optical fiber through the entrance side mirror,
Each of the incident side mirror and the emission side mirror is constituted by a dielectric multilayer film,
In any wavelength in the wavelength region of 616 nm ± 3 nm, the reflectance of the exit side mirror is 95% ± 1%,
At a wavelength of 605 nm, the reflectance of the incident side mirror is 99% or more, and the reflectance of the emission side mirror is 97% or more,
A fiber laser device, wherein, at a wavelength of 635 nm, the reflectance of the incident side mirror is 99% or more and the reflectance of the emission side mirror is 97% or more. An optical fiber having a core containing praseodymium ions as a luminescent substance that emits fluorescence, and a resonator composed of an incident side mirror disposed on one end face of the optical fiber and an output side mirror disposed on the other end face of the optical fiber In the fiber laser device that oscillates the laser light from the exit side mirror by making the excitation light incident on one end surface of the optical fiber through the entrance side mirror,
Each of the incident side mirror and the emission side mirror is constituted by a dielectric multilayer film,
In any wavelength in the wavelength region of 616 nm ± 3 nm, the reflectance of the exit side mirror is 95% ± 1%,
At a wavelength of 605 nm, the reflectance of the incident side mirror or the reflectance of the output side mirror is 90% or less,
A fiber laser device, wherein, at a wavelength of 635 nm, the reflectance of the incident side mirror is 99% or more and the reflectance of the emission side mirror is 97% or more. An optical fiber having a core containing praseodymium ions as a luminescent substance that emits fluorescence, and a resonator composed of an incident side mirror disposed on one end face of the optical fiber and an output side mirror disposed on the other end face of the optical fiber In the fiber laser device that oscillates the laser light from the exit side mirror by making the excitation light incident on one end surface of the optical fiber through the entrance side mirror,
Each of the incident side mirror and the emission side mirror is constituted by a dielectric multilayer film,
In any wavelength in the wavelength region of 616 nm ± 3 nm, the reflectance of the exit side mirror is 95% ± 1%,
At a wavelength of 605 nm, the reflectance of the incident side mirror or the reflectance of the output side mirror is 90% or less,
A fiber laser device, wherein a reflectance of the incident side mirror or a reflectance of the emission side mirror is 90% or less at a wavelength of 635 nm. An optical fiber having a core containing praseodymium ions as a luminescent substance that emits fluorescence, and a resonator composed of an incident side mirror disposed on one end face of the optical fiber and an output side mirror disposed on the other end face of the optical fiber In the fiber laser device that oscillates the laser light from the exit side mirror by making the excitation light incident on one end surface of the optical fiber through the entrance side mirror,
Each of the incident side mirror and the emission side mirror is constituted by a dielectric multilayer film,
In any wavelength in the wavelength region of 616 nm ± 3 nm, the reflectance of the exit side mirror is 95% ± 1%,
At a wavelength of 605 nm, the reflectance of the incident side mirror is 99% or more, and the reflectance of the emission side mirror is 97% or more,
A fiber laser device, wherein a reflectance of the incident side mirror is 90% or less at a wavelength of 635 nm.   The fiber laser device according to claim 4, wherein the reflectance of the output side mirror is 90% or less at a wavelength of 635 nm.

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