JP7396480B2 - Optical components and fiber laser equipment - Google Patents

Description

The present invention relates to highly efficient and highly stable optical components and laser devices.

Devices using crystal fibers have been developed for the purpose of laser oscillation and optical amplification. In Non-Patent Document 1, a mode-locked laser is configured using a Cr ⁴⁺ :Y3Al5O12 (Cr ⁴⁺ :YAG) single crystal fiber, and outputs an optical pulse with a pulse width of 120 fs at a center wavelength of 1.51 μm. This laser is used as a light source for a nonlinear optical microscope or a light source for generating THz waves.

In conventional optical components and fiber laser devices, as shown in FIGS. 14 to 17, when a single crystal fiber 81 is incorporated into a laser oscillator, it is attached to a dedicated fiber fixing stand 82 (Patent Document 1). 14, 15, and 16 are a top view, a front view, and a side view of the fiber fixing table 82, respectively. The fiber fixing table 82 used here has a structure in which two upper and lower metal blocks 821 and 822 are stacked. Straight grooves 823 and 824 each having a semi-elliptical cross section are formed on the inner surfaces of these two blocks. When they are stacked, they are in the same position, forming a hole with an oblong cross section.

As shown in FIG. 17, a single crystal fiber 81 is sandwiched between grooves 823 and 824 and fixed with a metal thin film interposed therebetween. This structure allows good heat removal, and by inducing appropriate stress birefringence in the single crystal fiber 81, it becomes possible to control the laser oscillation polarization. An end surface 92 of the fiber fixing table 82 is perpendicular to the direction of the grooves 823 and 824 in which the single crystal fiber 81 is sandwiched. According to Non-Patent Document 1, the single crystal fiber 81 has a diameter of 120 μm and a length of about 40 mm. The fiber fixing base 82 is also set to approximately the same length.

FIG. 18 shows a top view of the end portion of a conventional optical component or fiber laser device. The end of the single crystal fiber 81 fixed to the fiber fixing table 82 protrudes from the fixing table 82 by approximately 100 to 500 μm in length. Strictly matching the lengths of the single-crystal fiber 81 and the fixing table 82 (less than or equal to the oscillation wavelength) increases processing costs and is not realistic.

Furthermore, when the end surface 92 of the fixing base 82 and the end surface 91 of the single crystal fiber 81 are on the same plane, a buffering metal thin film covers the end surface 91 of the single crystal fiber 81, blocking a part of the optical path and lowering the oscillation efficiency. There is a risk of it being stored away. As described above, the protrusion 94 at the end of the single crystal fiber 81 is necessary in optical components and fiber laser devices.

Patent No. 5612540

Shigeo Ishibashi and Kazunori Naganuma, “Mode-locked operation of Cr4+:YAG single-crystal fiber laser with external cavity”, Opt. Express 22, 6764-6771 (2014). A. Yariv, "Fundamentals of Optoelectronics" 3rd edition, 1988, Maruzen, pp. 181-187.

However, while stress is applied to the portion 93 of the single crystal fiber 81 sandwiched between the fixing bases 82, stress is not applied to the protruding end portion (projection portion) 94. Therefore, a refractive index boundary is generated in the single crystal fiber 81 near the same surface 95 as the end surface of the fixing base 82 in the single crystal fiber 81, and the laser oscillation light 96 is reflected. (Actually, the oscillated light 96 and the reflected light 97 follow the same optical path, but in FIG. 18, the position of the reflected light 97 is shown shifted upwards in the paper to make it easier to distinguish between the oscillated light 96 and the reflected light 97.)

When this reflected light is mixed with the laser oscillation light, a sub-resonator is generated in the laser resonator, and the spectrum of the laser oscillation light 96 is periodically modulated (Non-Patent Document 2). As a result, there have been problems in that the threshold for mode-locked oscillation increases and two or more mode-locked pulses tend to occur within the resonator circuit.

In order to solve the above-mentioned problems, an optical component according to the present invention includes a single crystal fiber having a refractive index n, a fixing table , and an aperture stop , and the incident light passes through the aperture of the aperture stop. The light enters the end face of the single crystal fiber at an incident angle θ, is reflected on a plane including the end face of the fixing base in the single crystal fiber, and the reflected light is reflected on a plane parallel to the end face of the single crystal fiber. , when the plane on which the incident light travels and the plane on which the reflected light travels form an angle of 2γ, and the reflected light exits from the end face of the single crystal fiber at an exit angle θ', the fixed base When the perpendicular from the reflection point on the plane including the end face to the end face of the single crystal fiber is taken as the Z axis, the angle between the Z axis and the central axis of the single crystal fiber is α, and the angle of the end face of the fixing base is α. The angle between the normal and the central axis of the single crystal fiber is β, the distance between the end face of the single crystal fiber and the aperture stop is L, the radius of the aperture is d, and the following formula The output angle θ′ that satisfies (A) is an angle formed with the Z-axis, and the angle of rotation around the Z-axis from the plane in which the incident light travels is 2γ , and the direction in which the incident light enters and exits the fiber end face. It is characterized in that the angle formed by the oscillated light is larger than tan ⁻¹ (d/L).

According to the present invention, it is possible to provide an optical component and a laser device including a highly efficient and highly stable fiber amplifier and a fixing stand.

FIG. 1 is a schematic diagram of an optical component according to a first embodiment of the present invention. FIG. 2 is an external view of the optical component according to the first embodiment of the invention. FIG. FIG. 3 is an external view of the fixing base in the first embodiment of the present invention. FIG. 4 is a top view of the fixing table in the first embodiment of the present invention. FIG. 5 is a front view of the fixing base in the first embodiment of the present invention. FIG. 6 is a side view of the fixing base in the first embodiment of the present invention. FIG. 7 is a front view of the optical component according to the first embodiment of the invention. FIG. 8 is a top view of the vicinity of the end of the optical component according to the first embodiment of the present invention. FIG. 9 is a diagram showing the relationship between the fiber end face and the aperture stop in the first embodiment of the present invention. FIG. 10 is a top view of the vicinity of an end of an optical component according to a second embodiment of the present invention. FIG. 11 is a diagram showing trajectories of oscillated light and reflected light in the second embodiment of the present invention. FIG. 12 is a diagram showing trajectories of oscillated light and reflected light in the third embodiment of the present invention. FIG. 13 is a schematic diagram of a fiber laser device according to a fourth embodiment of the present invention. FIG. 14 is a top view of a fixing base in a conventional optical component. FIG. 15 is a front view of a fixing base in a conventional optical component. FIG. 16 is a side view of a fixing base in a conventional optical component. FIG. 17 is a front view of a fixing base in a conventional optical component. FIG. 18 is a top view of the vicinity of an end of a conventional optical component.

<First embodiment>
An optical component 10 according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 9.

<Configuration of optical components>
FIG. 1 shows a schematic diagram of an optical component 10 according to this embodiment. The optical component 10 includes a single crystal fiber 11 and a fixing table 12. Single crystal fiber 11 is fixed to a fixed base 12 . Further, two aperture stops 131 and 132 are arranged to face each other with the single crystal fiber 11 in between. The incident light 14 passes through the aperture of the aperture stop 131 and enters the single crystal fiber 11, and the outgoing light 15 passes through the aperture of the aperture stop 132 and exits.

FIG. 2 shows a bird's-eye view of the optical component 10 according to this embodiment (the aperture stops 131 and 132 are not shown). The fixing base 12 is composed of a pair of copper blocks 121 and 122. The single crystal fiber 11 is sandwiched from above and below by a pair of copper blocks 121 and 122 of the fixing table 12, and is fixed to the fixing table 12. The blocks 121 and 122 of the fixing base 12 may be made of a metal with good thermal conductivity, such as aluminum. Further, the fixed base 12 is fixed onto a copper base 21 by screws 22 at the four corners. Hereinafter, the direction substantially parallel to the central axis 16 of the fiber 11 will be referred to as "the central axis direction of the fiber 11."

The tip of the single crystal fiber 11 is fixed so as to protrude outward by about 200 μm from the end face 32 of the fixing table 12 . If the protrusion at the tip of the fiber 11 is too long, cooling by the fixing table 12 will not be sufficient. Furthermore, if the protrusion is too long, as will be described later, the reflected light may not be emitted from the end face 31 of the fiber 11, but may be totally reflected on the side surface of the fiber 11, affecting the laser light propagating within the fiber 11. There is. Therefore, the length of the protrusion is desirably 50 μm or more and 500 μm.

FIG. 3 shows a bird's eye view of the fiber fixing table 12. Moreover, a top view, a front view, and a side view of the fiber fixing table 12 are shown in FIGS. 4, 5, and 6, respectively.

The fiber fixing table 12 in this embodiment differs from conventional fiber fixing tables in that both end surfaces are inclined substantially parallel to each other. The surfaces of the two blocks 121 and 122 on the fixed base 12 that face each other when stacked (hereinafter referred to as "optical axis direction end faces") have substantially the same shape, and are aligned and stacked. Here, the end faces in the optical axis direction do not need to be perfectly aligned and overlapped, and a deviation may occur in the central axis direction of the fiber 11. This deviation is permissible as long as it is about 250 μm, and in this case, a step is created on the end surface 32 of the fixed base 12 at the boundary between the two blocks 121 and 122.

Straight grooves 123 and 124 are formed on each overlapping surface in order to fix the single crystal fiber 11. The cross-sectional shape of the grooves 123 and 124 is desirably semi-elliptical in order to dissipate heat and fix the light source single crystal.

When the respective surfaces of the blocks 121 and 122 are stacked facing each other, the grooves 123 and 124 formed on each surface overlap at the same position, forming a hole with an oval cross section as shown in FIG. be done. A Cr ⁴⁺ :YAG single crystal fiber 11 is sandwiched in this groove and fixed with an indium foil having a thickness of 5 μm to 50 μm interposed therebetween.

Although indium foil is used in this embodiment, the present invention is not limited to this, and flexible metal foil or resin foil may also be used. It is even better if the material has good thermal conductivity. This allows for good heat removal and induces appropriate stress birefringence in the single crystal fiber 11, thereby making it possible to control the laser oscillation polarization.

FIG. 7 shows a front view of the optical component 10 (the aperture stops 131 and 132 are not shown). Single crystal fiber 11 is fixed in grooves 123 and 124 of fixing table 12 . Here, since the single crystal fiber 11 has a diameter of 120 μm and a length of about 40 mm, the lengths of the grooves 123 and 124 of the fiber fixing table 12 are set to be approximately the same length.

In addition, the groove of the fixing base 12 has a semi-elliptical cross section, and in consideration of the thickness (5 μm to 50 μm) of the indium foil sandwiched between the block and the fiber 11, the groove is formed between the opposing block surfaces (facets). The spacing is 120 μm, the width is 150 μm, and the depth is 55 μm. The size of the groove of the fixing base 12 is not limited to this, and may be any size as long as it can suit the size of the fiber 11 and can fix the fiber 11 well.

<Operation principle of optical components>
The operating principle of the optical component 10 according to this embodiment will be explained. FIG. 8 shows a top view of the vicinity of one end face of the optical component 10 according to this embodiment. First, to simplify the explanation, if the end surface 31 of the fiber 11 and the end surface 32 of the fixing base 12 shown in FIG. A case will be described in which the inclination angles β of the 12 end faces 32 are equal.

Here, the inclination angle α of the end surface 31 of the fiber 11 is such that the normal line of the end surface 31 of the fiber 11 is in the central axis direction of the fiber 11 when the long axis of the generally elliptical end surface 31 of the fiber 11 is made parallel to the horizontal plane. Refers to the angle formed. On the other hand, the inclination angle β of the end surface 32 of the fixing table 12 refers to the angle between the normal line of the end surface 32 of the fixing table 12 and the central axis direction of the fiber 11.

The single crystal fiber 11 protrudes from the end face 32 of the fixing base 12 and is fixed thereto. In FIG. 8, only the component of the incident light (oscillation light) 41 that is incident on the end face 31 of the fiber 11 is shown for ease of explanation.

Stress is applied to the portion of the single crystal fiber 11 that is sandwiched between the fixing bases 12 . Hereinafter, the part to which this stress is applied will be referred to as the "stress applying part" 33. On the other hand, since the protrusion 34 at the tip of the single crystal fiber 11 is not sandwiched between the fixing bases 12, no stress is applied thereto.

As a result, near the end surface 32 of the fixing table 12, a refractive index difference occurs at the boundary between the stress applying part 33 and the protruding part 34 of the single crystal fiber 11, so that the incident light ( Oscillation light) 41 is reflected at this boundary. In other words, the incident light (oscillation light) 41 is reflected on the substantially same surface as the end surface 32 of the fixing base 12 inside the fiber 11 .

The end face 31 of the single crystal fiber 11 is obliquely polished so that its normal line forms an angle α with respect to the central axis direction of the fiber 11. Further, the normal line of the end face is set at an angle α with respect to the central axis direction of the fiber 11 so that the end face 32 of the fiber fixing table 12 is also parallel to the end face 31 of the single crystal fiber 11.

When the incident angle θ of the incident light (oscillation light) 41 with respect to the end face 31 of the fiber 11 satisfies equation (1) according to Snell's law, the incident light (oscillation light) 41 enters from the end face 31 of the fiber 11. , propagates inside the fiber 11 in the direction of the central axis of the fiber 11.

n is a refractive index, and in the case of Cr ⁴⁺ :YAG used in this embodiment, n=1.82.

Since a refractive index difference occurs between the protrusion 34 at the tip of the single crystal fiber 11 and the stress applying section 33 by the fiber fixing table 12, the incident light (oscillation light) 41 is reflected near the end surface 32 of the fiber fixing table 12. In other words, the incident light (oscillation light) 41 is reflected on the substantially same surface as the end surface 32 of the fixing base 12 inside the fiber 11 .

In this embodiment, since the end surface 32 of the fixed base 12 is inclined, the reflected light 42 propagates on a different optical path from the incident light (oscillation light) 41 propagating within the fiber 11. The angle between the reflected light 42 and the incident light (oscillation light) 41 propagating within the fiber 11 is 2θ.

Thereafter, the reflected light 42 is emitted from the end face 31 of the fiber 11. At this time, the output angle θ' is equal to the incident angle.

Therefore, the angle at which the reflected light 42 reflected by the end surface 32 of the fixed base 12 propagates within the fiber 11 and enters the end surface 31 of the fiber 11 (the angle made with the normal to the end surface 31 of the fiber 11) is α, Since the output angle θ' (=θ) from the end face 31 of the fiber 11 is the output angle θ′ (=θ) at which the reflected light 42 exits from the end face 31 of the fiber 11, the angle θ at which the reflected light 42 exits from the end face 31 of the fiber 11 satisfies equation (1).

In order to avoid the emitted reflected light 42 from affecting the oscillation light 41, it is necessary to prevent the reflected light 42 from entering the aperture stops 131 and 132. Therefore, as shown in FIG. 9, when the distance of the aperture stops 131 and 132 from the end face 31 of the fiber 11 is L, and the diameter of the aperture of the aperture stops 131 and 132 is 2d, it is necessary to satisfy equation (2). be.

According to the optical component 10 according to the present embodiment, the reflected light 42 from the reflection point in the single crystal fiber 11 does not remain in the resonator, and does not modulate the longitudinal mode distribution of the oscillated light 41. .

In this embodiment, the inclination angle of the end face 31 of the fiber 11 is α = 4.5°, the aperture diameter of the aperture stops 131 and 132 and the distance from the end face 31 of the fiber 11 are 2d = 24 mm and L = 50 mm, respectively. Therefore, 2θ=16.4°, tan ⁻¹ (d/L)=13.5°, and equation (2) is satisfied.

<Second embodiment>
An optical component 50 according to a second embodiment of the present invention will be described with reference to FIGS. 10 to 11.

The optical component 50 according to this embodiment has substantially the same configuration as the first embodiment, but differs in that the fiber end surface 31 and the end surface 32 of the fixing base 12 are non-parallel.

<Configuration of optical components>
FIG. 10 shows a top view of the vicinity of one end face of the optical component 50 according to this embodiment. Here, the perpendicular line from the reflection point 51 on the plane including the end surface 32 of the fixing base 12 to the end surface 31 of the fiber 11 is defined as the Z-axis 52. FIG. 11 is a diagram showing the vicinity of one end face of the optical component 50 similar to FIG. 10 in coordinates with the Z-axis 52 in the vertical direction of the paper. Here, the arrow 53 in FIG. 10 indicates the positive direction of the angle.

The end face 31 of the fiber is inclined, and the normal line of the fiber end face 31 forms an inclination angle α with the direction of the central axis of the fiber 11. Further, the end face 32 of the fixing base 12 is inclined in the same direction as the fiber end face 31, and the normal line of the end face 32 of the fixing base 12 forms an inclination angle β with the advancing direction.

Here, the case of tilting in the same direction means a plane on which the incident light (oscillation light) 41 enters the fiber 11 and propagates within the fiber 11 (hereinafter referred to as "oscillation light traveling plane"), as shown in FIG. ) 54, the normal line of the fiber end face 31, and the normal line of the end face 32 of the fixing base 12 are parallel to each other. Here, the normal line of the end surface 32 of the fixed base 12 forms an angle α-β with respect to the Z-axis 52.

At this time, the reflected light 42 travels in the same direction as the traveling direction of the incident light 41 when viewed from above the fiber end face 31, in other words, on the parallel plane of the fiber end face 31.

<Operation principle of optical components>
The operating principle of the optical component 50 according to this embodiment will be explained. The incident light (oscillation light) 41 enters the fiber 11 at an incident angle θ, propagates inside the fiber 11 parallel to the traveling direction, and near the end face 32 of the fixed base 12 at an angle of 2β with the central axis direction of the fiber 11. It is reflected, reaches the fiber end face 31 at an angle α-2β, and is emitted from the fiber end face 31 at an output angle θ′.

Therefore, the output angle θ' of the reflected light 42 output from the fiber end face 31 satisfies equation (3). Furthermore, in order to avoid the reflected light 42 from entering the aperture stops 131 and 132, it is necessary to satisfy equation (4).

According to the optical component 50 according to the present embodiment, the reflected light 42 from the reflection point in the single crystal fiber 11 does not stay in the resonator, and does not modulate the longitudinal mode distribution of the oscillated light 41. .

<Third embodiment>
An optical component 60 according to a third embodiment of the present invention will be described with reference to FIG. 12.

The optical component 60 according to this embodiment has substantially the same configuration as the first embodiment, but differs in that the fiber end surface 31 and the end surface 32 of the fixing base 12 are non-parallel. Furthermore, although it has substantially the same configuration as the second embodiment, it differs in that the normal to the end surface 32 of the fixed base 12 is non-parallel to the oscillation light traveling surface 54.

In the optical component 60 according to the present embodiment, the end surface 32 of the fixing base 12 is inclined in an arbitrary direction, so that the reflected light 42 also travels in an arbitrary direction. In this embodiment, it is assumed that a surface 55 on which reflected light 42 travels (hereinafter referred to as "reflected light traveling surface") relative to oscillation light traveling surface 54 rotates at a predetermined angle around Z-axis 52. In other respects, it is assumed that the optical paths of the incident light and the reflected light 42 are substantially the same as in the second embodiment. Here, as in the second embodiment, the perpendicular line from the reflection point 51 on the plane including the end surface 32 of the fixing base 12 to the end surface 31 of the fiber 11 is defined as the Z axis 52. Details are explained below.

<Configuration of optical components>
FIG. 12 is a diagram showing the vicinity of one end face of the optical component 60 according to the present embodiment in coordinates with the Z-axis 52 in the vertical direction of the paper.

The fiber end face 31 is inclined, and the normal line of the fiber end face 31 forms an inclination angle α with the direction of the central axis of the fiber 11. Further, it is assumed that the end face 32 of the fixed base 12 is inclined, and the normal line of the end face 32 of the fixed base 12 forms an angle α−β with respect to the Z axis 52.

<Operation principle of optical components>
The operating principle of the optical component 60 according to this embodiment will be explained. The incident light (oscillation light) 41 enters the fiber at an incident angle θ and propagates within the fiber in the direction of the central axis of the fiber 11. Here, the incident light (oscillation light) 41 travels in the same plane (oscillation light traveling plane) 54.

Next, the incident light (oscillation light) 41 is reflected at a reflection point 51 near the end surface 32 of the fixed base 12.

Here, if the normal line of the end surface 32 of the fixed base 12 is on a plane rotated by an angle γ around the Z-axis 52 from the oscillation light traveling plane, the reflected light 42 will be rotated around the Z-axis 52 as the rotation axis. The oscillation light travels on a surface (reflected light travel surface) 55 rotated by an angle of 2γ from the oscillation light travel surface 54 . In this way, when viewed from above the fiber end face 31, in other words, the reflected light 42 travels in a direction forming an angle 2γ with the traveling direction of the incident light (oscillation light) 41 on the parallel plane of the fiber end face 31. .

Similar to the second embodiment, the reflected light 42 on the reflection progressing surface reaches the fiber end face 31 at an incident angle α-2β and exits at an output angle θ'.

Therefore, as shown in FIG. 12, the output angle θ' of the reflected light 42 from the fiber end face 31 satisfies equation (5) according to Snell's law.

In order to avoid the reflected light 42 from entering the aperture stops 131 and 132, the incident angle θ of the incident light (oscillation light) 41, the output angle θ' of the reflected light 42, and the oscillation light traveling surface 54 must be adjusted. The angle formed by the incident light 41 and the reflected light 42 defined by the angle 2γ formed by the reflected light traveling surface 55 needs to be larger than tan ⁻¹ (d/L).

According to the optical component 60 according to the present embodiment, the reflected light 42 from the reflection point in the single crystal fiber 11 does not remain in the resonator, and does not modulate the longitudinal mode distribution of the oscillated light 41. .

<Fourth embodiment>
A laser device 70 according to a fourth embodiment of the present invention will be described with reference to FIG. 13.

FIG. 13 shows a laser device 70 according to this embodiment. The laser device 70 includes an optical component 10 according to the first implementation, two aperture stops 131 and 132 facing each other with the optical component 10 in between, and the concave mirror facing the optical component 10 and the aperture stops 131 and 132 in between. 71 and 72, a condenser lens 73, and a pump light source 74. In this way, in the laser device 70, the concave mirrors 71 and 72 are provided to form a resonator structure.

The radius of curvature of the concave mirrors 71 and 72 is 100 mm. One concave mirror 71 has a reflectance of 99.9% for light with a wavelength of 1.40 μm to 1.60 μm, and the other concave mirror 72 is an output coupling mirror and has a reflectance of 99.9% for light with a wavelength of 1.40 μm to 1.60 μm. It has a transmittance of 1% for wavelength light. Further, the focal length of the condensing lens 73 is 120 mm. Further, the pump light source 74 emits pump light having a wavelength of 1.064 μm.

As a result of condensing the pump light emitted from the pump light source 74 with the condensing lens 73 and causing laser oscillation, the influence of the reflected light at the stress applying part in the single crystal fiber 11 is suppressed, and noise is reduced. oscillation light can be obtained.

In this embodiment, the optical components according to the first embodiment are used, but similar results can be obtained even if the optical components according to the second and third embodiments are used.
In this embodiment, the laser resonator includes two mirrors, but three or more mirrors may be used to configure the laser resonator in a Z-shape, an X-shape, or a ring-shape structure. Same results.

It is clear that the embodiments of the present invention are effective not only for fixing Cr ⁴⁺ :YAG single crystal fibers but also for fixing single crystal fibers using other laser crystals. As a laser crystal, a YAG crystal doped with Yb, Nd, Er, Tm, or Ho, a Ti sapphire crystal, or a Cr forsterite crystal can be used. It is also effective when using polycrystalline fibers.

In the embodiment of the present invention, when the fixing base is installed on a horizontal surface, two blocks are placed above and below the fiber to sandwich and fix the fiber. The fiber may be sandwiched and fixed.

In the embodiment according to the present invention, a case is shown in which both end surfaces of the fixing base are substantially parallel, but the present invention is not limited to this. Even if the respective end faces are not substantially parallel, it is sufficient to satisfy the conditions according to equations (1) to (5) in each of the first to third embodiments.

In the embodiment of the present invention, an example of the structure, dimensions, materials, etc. of each component is shown in the configuration and operating principle of the optical component and the laser device, but the invention is not limited thereto. Any material may be used as long as it exhibits the functions and effects of the optical component and laser device according to the embodiment of the present invention.

The present invention can be applied to optical communication equipment and systems in the information and communication field, as well as material processing in the industrial field and the medical field.

10 Optical components 11 Single crystal fiber 12 Fixed base 131, 132 Aperture stop 16 Central axis of single crystal fiber 31 End face of single crystal fiber 32 End face of fixed base 41 Incident light 42 Reflected light

Claims (4)

comprising a single crystal fiber having a refractive index n, a fixing table , and an aperture stop ,
The incident light passes through the aperture of the aperture stop and enters the end face of the single crystal fiber at an incident angle θ,
reflected on a plane including the end face of the fixed base in the single crystal fiber;
The reflected light travels on a parallel plane of the end face of the single crystal fiber, with the plane in which the incident light travels and the plane in which the reflected light travels forming an angle of 2γ,
When the reflected light is emitted from the end face of the single crystal fiber at an exit angle θ′, when the Z axis is a perpendicular line from a reflection point on a plane including the end face of the fixing base to the end face of the single crystal fiber, the angle between the Z axis and the central axis of the single crystal fiber is α,
the angle between the normal to the end surface of the fixing base and the central axis of the single crystal fiber is β;
the distance between the end face of the single crystal fiber and the aperture stop is L;
the radius of the opening is d;
The output angle θ' that satisfies the following formula (A) is an angle with the Z axis, and the direction in which the rotation angle around the Z axis from the plane in which the incident light travels is 2γ , and the fiber end face An optical component characterized in that an angle formed by input and output oscillation light is larger than tan ⁻¹ (d/L).

The plane on which the reflected light travels and the plane on which the incident light travels are the same plane,
The optical component according to claim 1, characterized in that the following formula (B) is satisfied.

the angle α and the angle β are equal,
The optical component according to claim 2 , characterized in that the following formulas (C) and (D) are satisfied.

The optical component according to any one of claims 1 to 3 , another aperture stop disposed on the opposite side of the aperture stop with respect to the optical component, and a plurality of mirrors forming a resonator. , a fiber laser device comprising a condensing lens and a pump light source.

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