Optical fibers with end caps, fiber arrays, light source devices, and wavelength beam coupling devices

Abstract

The present invention provides an end capped optical fiber that can reduce the angular misalignment of the optical axis of a collimated light beam. [Solution] The optical fiber with an end cap comprises an optical fiber and an end cap having a first surface connected to the end face of the optical fiber, a second surface located opposite the first surface, and a side surface connecting the first and second surfaces. The end cap includes a convex lens, the second surface includes the convex lens surface, and the side surface includes an outer surface surrounding the optical axis of the convex lens. The angle formed by each of the two intersecting lines between the virtual plane containing the optical axis and the outer surface with respect to the optical axis changes as the virtual plane rotates once around the optical axis.

Description

Technical Field

[0001] The present disclosure relates to an end - capped optical fiber, a fiber array, a light source device, and a wavelength beam combining device.

Background Art

[0002] An end - capped optical fiber is an optical element including an optical fiber and an end - cap fused to an end face of the optical fiber. The end - cap may include a function as a collimating lens that collimates and emits light propagating through the optical fiber according to the application. Patent Document 1 discloses an example of an end - capped optical fiber in which the end - cap includes a collimating lens.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] To provide an end - capped optical fiber capable of reducing an angular deviation of the optical axis of a collimated light beam.

Means for Solving the Problems

[0005] In one embodiment, the end - capped optical fiber of the present disclosure includes an optical fiber, a first surface connected to an end face of the optical fiber, a second surface located on the opposite side of the first surface, and an end - cap having a side surface connecting the first surface and the second surface. The end - cap includes a convex lens, the second surface includes a convex lens surface, the side surface includes an outer peripheral surface surrounding the optical axis of the convex lens, and an angle formed by each of two intersection lines between a virtual plane including the optical axis and the outer peripheral surface with respect to the optical axis changes while the virtual plane rotates once around the optical axis.

[0006] In one embodiment, the fiber array of the present disclosure comprises a plurality of end-capped optical fibers, each of which is an end-capped optical fiber, and a support member that supports the outer peripheral surface of the end cap in each of the plurality of end-capped optical fibers, wherein the second surfaces of the end caps in each of the plurality of end-capped optical fibers face the same side, and the shortest distance from the connection point between the optical fiber and the end cap to the support member is different in at least two of the plurality of end-capped optical fibers.

[0007] In one embodiment, the light source device of the present disclosure includes: a fiber array, wherein the plurality of end-capped optical fibers include a first end-capped optical fiber and a second end-capped optical fiber; a first laser light source that emits a first laser beam, wherein the first laser beam is coupled to the optical fiber included in the first end-capped optical fiber from the side opposite to the end cap; and a second laser light source that emits a second laser beam, wherein the second laser beam is coupled to the optical fiber included in the second end-capped optical fiber from the side opposite to the end cap.

[0008] In one embodiment, the wavelength beam coupling apparatus of the present disclosure comprises a light source apparatus, wherein the first laser light has a first peak wavelength and the second laser light has a second peak wavelength different from the first peak wavelength, and a diffraction grating, wherein the first end cap optical fiber emits a first light beam collimated with the first laser light from the second surface of the end cap, the second end cap optical fiber emits a second light beam collimated with the second laser light from the second surface of the end cap, and the diffraction grating wavelength-combines the first light beam and the second light beam. [Effects of the Invention]

[0009] According to embodiments of this disclosure, it is possible to realize an optical fiber with an end cap that can reduce the angular misalignment of the optical axis of the optical beam. [Brief explanation of the drawing]

[0010] [Figure 1A] Figure 1A is a schematic diagram showing the configuration of an end-capped optical fiber in an ideal state. [Figure 1B] Figure 1B is a schematic diagram showing the trajectory of the center of the light beam obtained by rotating the end cap around the optical axis of the convex lens in the ideal state shown in Figure 1A. [Figure 2] Figure 2 is a schematic diagram illustrating the deviation of the optical beam's optical axis from the optical axis of the lens when eccentricity occurs between the central axis of the fiber and the optical axis of the lens in the comparative example of an end-capped optical fiber. [Figure 3A] Figure 3A is a schematic diagram showing the configuration of an end-capped optical fiber in a comparative example. [Figure 3B] Figure 3B is a schematic diagram showing the trajectory T of the optical axis of the light beam in the comparative example. [Figure 4] Figure 4 is a schematic diagram showing the general configuration of an end-capped optical fiber in an exemplary embodiment of the present disclosure. [Figure 5A] Figure 5A is a schematic cross-sectional view of the end cap. [Figure 5B] Figure 5B is a schematic front view showing the first surface of the end cap. [Figure 5C] Figure 5C is a schematic front view showing the second surface of the end cap. [Figure 6A] Figure 6A is another cross-sectional view schematically showing the end cap. [Figure 6B] Figure 6B is another front view schematically showing the first surface of the end cap. [Figure 6C] Figure 6C is another front view schematically showing the second surface of the end cap. [Figure 7A]FIG. 7A is a schematic diagram showing an optical fiber with an end cap in a state where there is no deviation between the central axis of the fiber and the optical axis of the lens due to fusion of the optical fiber and the end cap. [Figure 7B] FIG. 7B is a schematic diagram showing the optical trajectory of the light beam in the state shown in FIG. 7A. [Figure 8A] FIG. 8A is a schematic diagram showing an optical fiber with an end cap in a state where there is a deviation between the central axis of the fiber and the optical axis of the lens due to fusion of the optical fiber and the end cap. [Figure 8B] FIG. 8B is a schematic diagram showing the optical trajectory of the light beam in the state shown in FIG. 8A. [Figure 9] FIG. 9 is a diagram schematically showing a configuration example of a main optical fiber. [Figure 10] FIG. 10 is a top view schematically showing the configuration of a fiber array according to an exemplary embodiment of the present disclosure. [Figure 11] FIG. 11 is a front view schematically showing the configuration of a fiber array according to an exemplary embodiment of the present disclosure. [Figure 12] FIG. 12 is a diagram schematically showing the configuration of a light source device according to an exemplary embodiment of the present disclosure. [Figure 13] FIG. 13 is a diagram schematically showing the configuration of a wavelength beam combining device according to an exemplary embodiment of the present disclosure.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, an optical fiber with an end cap, a fiber array, a light source device, and a wavelength beam combining device according to an embodiment of the present disclosure will be described with reference to the drawings. Parts denoted by the same reference numerals in the plurality of drawings indicate the same or equivalent parts.

[0012] Furthermore, the embodiments described below are illustrative examples to embody the technical concept of the present invention and do not limit the present invention to these examples. Also, descriptions of the size, material, shape, and relative arrangement of the components are intended as examples only, and are not intended to limit the scope of the present invention to those examples alone. The size and positional relationships of the components shown in each drawing may be exaggerated for ease of understanding.

[0013] The attached diagram schematically shows mutually orthogonal X, Y, and Z axes for reference. The Z axis represents the optical axis direction of the convex lens on the end cap 21. The direction of the arrow on the X axis is referred to as the +X direction, and the opposite direction is referred to as the -X direction. When the ±X directions are not distinguished, they are simply referred to as the X direction. The same applies to the Y and Z directions. This does not restrict the orientation of the optical elements or devices shown in the diagram when they are used; the orientation of the optical elements or devices is arbitrary.

[0014] Before describing embodiments of this disclosure, an ideal state of an end-capped optical fiber will be described with reference to Figure 1A. The ideal state is one in which there is no misalignment of the optical axis of the optical fiber and the convex lens due to the fusion of the optical fiber and the end cap.

[0015] Figure 1A is a schematic diagram showing the configuration of an end-capped optical fiber in an ideal state. The end-capped optical fiber 110 comprises an optical fiber 11 and an end cap 21 having a convex lens. In Figure 1A, the central axis 70a of the optical fiber 11, the optical axis 70b of the convex lens of the end cap 21, and the optical axis 70c of the light beam that propagates through the optical fiber 11 and is emitted from the end face of the optical fiber 11 are shown by dashed, dotted, and solid lines, respectively. Hereafter, the central axis of the optical fiber and the optical axis of the convex lens will be referred to as the "optical axis of the fiber" and the "optical axis of the lens," respectively.

[0016] The end cap 21 shown in Figure 1A has a shape symmetrical with respect to the optical axis 70b of the lens. Specifically, the end cap 21 has a side or outer surface with a cross-section parallel to a plane perpendicular to the optical axis 70b of the lens, which is uniformly circular along the optical axis. In an ideal state, the central axis 70a of the fiber and the optical axis 70b of the lens are coaxial, and the optical axes 70b and 70c of the lens and the optical beam are coaxial.

[0017] However, aligning the optical axes 70b and 70c of the lens and light beam coaxially is not easy. In fact, when the optical fiber is fused to the end cap during manufacturing, a misalignment often occurs between the central axis of the fiber and the optical axis of the lens.

[0018] Referring to Figures 2, 3A, and 3B, the configuration of the end capped optical fiber in the comparative example is described. In contrast to the ideal state, in the comparative example, the fusion of the optical fiber 11 and the end cap 21 causes the central axis 70a of the fiber to be offset from the optical axis 70b of the lens. In other words, the central axis 70a of the fiber is eccentric with respect to the optical axis 70b of the lens. Therefore, the central axis 70a of the fiber and the optical axis 70b of the lens are not coaxial, and consequently, the optical axes 70b and 70c of the lens and the optical beam are not coaxial.

[0019] In this specification, "not coaxial" generally means that the two axes do not coincide, and more specifically, that the eccentricity of the central axis 70a of the fiber from the optical axis 70b of the lens exceeds 0.1 μm. In contrast, "coaxial" generally means that the two axes coincide, and more specifically, that the eccentricity of the central axis 70a of the fiber from the optical axis 70b of the lens is 0.1 μm or less.

[0020] Figure 2 is a schematic diagram illustrating the deviation of the optical axis 70c of the optical beam from the optical axis 70b of the lens in the comparative example of an end-capped optical fiber 111, where eccentricity occurs between the central axis 70a of the fiber and the optical axis 70b of the lens. Figure 3A is a schematic diagram showing the configuration of the end-capped optical fiber 111 in the comparative example. Figure 3B is a schematic diagram showing the trajectory T of the center of the optical beam in the comparative example.

[0021] The optical axis 70c of the light beam lies on a straight line connecting the center of the core of the optical fiber 11 and the center 29c of the convex lens surface 29. Figure 2 shows a virtual plane P1 perpendicular to the optical axis 70b of the lens, with mutually orthogonal X and Y axes shown within the virtual plane P1. The optical axis 70b of the lens passes through the intersection point O of the X and Y axes (i.e., the origin of the XY plane).

[0022] The fusion of the optical fiber 11 and the end cap 21 causes eccentricity between the central axis 70a of the fiber and the optical axis 70b of the lens. As a result, the central axis 70a of the fiber does not coincide with the optical axis 70b of the lens. Consequently, the optical axis 70c of the light beam does not coincide with the optical axis 70b of the lens, forming an angle θ with respect to the optical axis 70b of the lens. In this specification, this angle θ may be referred to as the "angle shift of the optical axis." The trajectory of the virtual plane P1 shown in Figure 2 indicates the central position of the light beam due to the angle shift of the optical axis.

[0023] When the optical axes of both the light beam and the lens are misaligned, rotating the end cap 21 to which the optical fiber 11 is fused 360° around the optical axis 70b of the lens results in a trajectory T of the center of the light beam being drawn on a virtual plane P1. In the examples shown in Figures 2 and 3B, the trajectory T of the center of the light beam does not pass through the origin of the XY plane. The trajectory T of the center of the light beam is approximately circular. The center of the circle roughly coincides with the origin of the XY plane. However, the shape of the trajectory T is not limited to a circle. The size of the circle of the trajectory T mainly depends on the eccentricity of the central axis 70a of the fiber from the optical axis 70b of the lens. The position of the center of the circle of the trajectory T on the XY plane depends on the degree of eccentricity between the central axis 70a of the fiber and the optical axis 70b of the lens. Details of the fiber array will be described later.

[0024] In the comparative example, because the trajectory T does not pass through the origin of the XY plane, an angular misalignment occurs in the optical axis of the light beam relative to the optical axis 70b of the lens. The greater the degree of eccentricity between the central axis 70a of the fiber and the optical axis 70b of the lens, the greater the angular misalignment of the optical axis of the light beam.

[0025] Figure 1B shows the trajectory T of the center of the light beam obtained by rotating the end cap 21 360° around the optical axis 70b of the lens in the ideal state shown in Figure 1A. In the ideal state, since the central axis 70a of the fiber and the optical axis 70b of the lens are coaxial, the central axis of the light beam remains at the origin of the XY plane even when the end cap 21 is rotated 360° around the optical axis 70b of the lens.

[0026] To solve this problem, in the end cap of the embodiment of the present disclosure, the angle formed by each of the two intersecting lines between the virtual plane containing the optical axis of the lens and the outer surface with respect to the optical axis of the lens changes as the virtual plane rotates once around the optical axis. With such an end cap structure, even if the central axis of the fiber and the optical axis of the lens are misaligned due to the fusion of the optical fiber and the end cap, the angular misalignment between the optical axis of the lens and the optical axis of the optical beam can be reduced by rotating the end cap around the optical axis of the lens while supporting the outer surface of the end cap, for example, by a groove in a support member.

[0027] (Embodiment) [Optical fiber with end caps] An end capped optical fiber according to one embodiment of the present disclosure comprises an optical fiber and an end cap having a first surface connected to the end face of the optical fiber, a second surface located opposite to the first surface, and a side surface connecting the first surface and the second surface, wherein the end cap includes a convex lens, the second surface includes a convex lens surface, and the side surface includes an outer peripheral surface surrounding the optical axis of the convex lens, and the angle formed with respect to the optical axis by each of two intersecting lines between a virtual plane including the optical axis and the outer peripheral surface changes as the virtual plane rotates once around the optical axis.

[0028] In this specification, "collimated light beam" includes not only light beams that are perfectly parallel, but also light beams with reduced divergence. The divergence angle (total angle) of a sufficiently collimated light beam may be, for example, 0.4° or less.

[0029] First, the schematic configuration of the end-capped optical fiber according to this embodiment will be described with reference to Figure 4. Figure 4 is a schematic diagram showing the schematic configuration of the end-capped optical fiber in this embodiment.

[0030] The optical fiber 100 with an end cap shown in Figure 4 comprises an optical fiber 10 that propagates light and an end cap 20 connected to the optical fiber 10 that emits the light propagating through the optical fiber 10 as a collimated light beam (hereinafter simply referred to as "light beam"). The optical fiber 10 is fused to the end cap 20. The light propagating through the optical fiber 10 may be laser light or LED light. The optical fiber 10 may be, for example, a multimode fiber. The optical fiber 10 may also be a single-mode fiber, but the use of a multimode fiber is advantageous in that it can propagate high-power light. The core of the multimode fiber may be formed from, for example, quartz, which is resistant to damage from high-power light.

[0031] The end cap 20 has a first surface 22a connected to the end face of the optical fiber 10, a second surface 22b located on the opposite side of the first surface 22a, and a side surface 22h connecting the first surface 22a and the second surface 22b. The end cap 20 includes a convex lens, and the second surface 22b includes a convex lens surface 29. The convex lens surface 29 collimates and emits light propagating through the optical fiber 10. The side surface 22h includes an outer circumferential surface surrounding the optical axis 70b of the convex lens.

[0032] In Figure 4, the central axis 70a of the fiber and the optical axis 70b of the lens are shown by dashed and dotted lines, respectively. The optical axis 70b of the lens extends along a straight line passing through the center 29c of the convex lens (see Figure 5C) and perpendicular to the second surface 22b, which functions as the convex lens surface. When the optical fiber 10 is fused to the end cap 20, eccentricity may occur between the central axis 70a of the fiber and the optical axis 70b of the lens. In the example shown in Figure 4, the central axis 70a of the fiber is offset from the optical axis 70b of the lens. In other words, the central axis 70a of the fiber is eccentric with respect to the optical axis 70b of the lens.

[0033] Figures 5A to 6C are schematic diagrams illustrating the external shape of the end cap 20. Figures 5A, 5B, and 5C show a cross-sectional view of the end cap 20, a front view of the first surface 22a of the end cap 20, and a front view of the second surface 22b of the end cap 20, respectively. Figures 5B and 6B show the support members 42 that support the end cap 20. The cross-section of the end cap 20 shown in Figure 5A corresponds to the cross-section of the end cap 20 along the VA-VA line in the front view of the first surface 22a of the end cap 20 shown in Figure 5B.

[0034] Figures 6A, 6B, and 6C show other cross-sectional views of the end cap 20, another front view of the first surface 22a of the end cap 20, and another front view of the second surface 22b of the end cap 20, respectively. The cross-section of the end cap 20 shown in Figure 6A corresponds to the cross-section of the end cap 20 along the VIA-VIA line in the front view of the first surface 22a of the end cap 20 shown in Figure 6B.

[0035] The end cap 20 shown in Figure 6A represents the end cap 20 shown in Figure 5A rotated 90° around the optical axis 70b of the lens. In the example of the end cap shown in Figure 5A, as shown in Figure 5B, the size x1 in the +X direction and the size x2 in the -X direction of the first surface 22a of the end cap 20 relative to the optical axis 70b of the lens are equal. The size y1 in the +Y direction and the size y2 in the -Y direction of the first surface 22a of the end cap 20 relative to the optical axis 70b of the lens are different. Among the sizes x1, x2, y1, and y2, sizes x1, x2, and y2 are equal. Thus, on the first surface 22a, it is sufficient that at least one of the sizes x1, x2, y1, and y2 is different from the others. On the other hand, as shown in Figure 5C, the size x1 in the +X direction, the size x2 in the -X direction, the size y1 in the +Y direction, and the size y2 in the -Y direction of the second surface 22b of the end cap 20 relative to the optical axis 70b of the lens are all equal.

[0036] In the example of the end cap shown in Figure 5A, the sizes x1 and x2 of the first surface 22a of the end cap 20 are equal, but they may be different. For example, size x1 may be equal to size y1, or it may be different in size from size x2 or y1.

[0037] The thickness of the end cap 20 along the optical axis 70b of the lens, that is, the distance from the first surface 22a to the second surface 22b, is, for example, between 2 mm and 100 mm. The absolute value of the difference between two sizes selected from the sizes x1, x2, y1, and y2 of the first surface 22a of the end cap 20 may be, for example, 10 mm or less, 5 mm or less, or 1 mm or less. This size difference may be appropriately changed depending on the on-axial thickness of the end cap 20.

[0038] Figures 5A and 6A show a virtual plane P2 containing the optical axis 70b of the lens, which defines two intersecting lines 25a and 25b in the cross-section of the end cap 20. The side surface of the end cap 20 includes the outer circumferential surface 22c surrounding the optical axis 70b of the lens. In the cross-section of the end cap 20 shown in Figure 5A or Figure 6A, the upper and lower portions where the virtual plane P2 and the outer edge of the outer circumferential surface 22c intersect, with respect to the optical axis 70b of the lens, are called intersecting lines 25a and 25b, respectively. The angle that intersecting line 25a makes with respect to the optical axis 70b of the lens is called angle θ1, and the angle that intersecting line 25b makes with respect to the optical axis 70b of the lens is called angle θ2.

[0039] In the example shown in Figure 5A, angle θ1 is greater than zero, and angle θ2 is zero. In other words, the intersecting line 25a is inclined with respect to the optical axis, and the intersecting line 25b is parallel to the optical axis. Here, the angle zero does not have to be exactly 0°, but includes, for example, a range of 0° or more and less than 0.005°.

[0040] The outer shape of the outer surface 22c of the end cap 20 is determined by the inclination angle of the intersecting line with respect to the optical axis 70b of the lens, and can be appropriately determined according to the amount of eccentricity between the central axis 70a of the fiber and the optical axis 70b of the lens.

[0041] The two intersecting lines 25a and 25b may be nonparallel at a certain angle of rotation around the optical axis of the virtual plane P2. Figure 5A shows an example of the state in which the two intersecting lines 25a and 25b are nonparallel at a certain angle of rotation. The two intersecting lines 25a and 25b may be nonparallel, for example, while the virtual plane P2 rotates at least 1 / 4 turn (i.e., 90°) around the optical axis 70b of the lens.

[0042] The virtual plane P2 shown in Figure 6A is the virtual plane P2 shown in Figure 5A rotated 90° around the optical axis 70b of the lens. In the cross-section of the end cap 20 shown in Figure 6A, the angle θ1 that the intersecting line 25a makes with respect to the optical axis 70b of the lens, and the angle θ2 that the intersecting line 25b makes with respect to the optical axis 70b of the lens, are both 0°. In other words, the two intersecting lines 25a and 25b are parallel to the optical axis 70b of the lens and are parallel to each other.

[0043] Thus, each of the angles θ1 and θ2 changes while the virtual plane P2 rotates 360° around the optical axis 70b of the lens. For example, at least one of the angles θ1 and θ2 may change continuously while the virtual plane P2 rotates within a range of rotation angles (e.g., 90°) around the optical axis 70b of the lens.

[0044] The outer circumferential surface 22c of the end cap 20 may include a region where the angle of one of the two intersecting lines 25a and 25b is zero while the virtual plane P2 rotates around the optical axis 70b of the lens within a certain range of rotation angles. The region 22e of the outer circumferential surface 22c shown in Figures 5A and 6A respectively is an example of such a zero angle region. In the region 22e shown in Figure 5A, the angle θ2 of the intersecting line 25b is zero. In the region 22e shown in Figure 6A, the angles θ1 and θ2 of both intersecting lines 25a and 25b are zero. For example, if the optical axis 70b of the lens and the central axis 70a of the fiber are coaxial, supporting the region 22e of the outer circumferential surface 22c with a support member 42 (described later) can easily reduce the angular misalignment between the optical axis 70b of the lens and the optical axis of the light beam.

[0045] The outer circumferential surface 22c of the end cap 20 may include a region where the angle of one of the two intersecting lines 25a and 25b changes within a range of, for example, 0.005° to 1° while the virtual plane P2 rotates half a turn (180°) around the optical axis 70b of the lens. The region 22f of the outer circumferential surface 22c shown in Figure 5A is an example of a region where the angle changes within a range of 0.005° to 1°. In the region 22f shown in Figure 5A, the angle θ1 of the intersecting line 25a of the two intersecting lines 25a and 25b may be 0.005° to 1°. For example, if the optical axis 70b of the lens and the central axis 70a of the fiber are misaligned, supporting the region 22f of the outer circumferential surface 22c with the support member 42 described later can easily reduce the angular misalignment between the optical axis 70b of the lens and the optical axis of the light beam. This is because when the end cap 20 is rotated around the optical axis 70b of the lens, the position of the end cap 20 supported by the groove 43 in the support member 42 changes, causing the end cap 20 to tilt. However, the groove 43 in the support member 42 is not limited to a V-shaped groove as shown in Figures 5B, 5C, 6B, and 6C, but may also be a rectangular groove. Furthermore, for example, if the end cap 20 can be supported by the support member 42, the groove 43 is not necessarily required.

[0046] Figure 7A is a schematic diagram showing an end-capped optical fiber 100 in a state where there is no misalignment in the central axis 70a of the fiber and the optical axis 70b of the lens due to the fusion of the optical fiber 10 and the end cap 20. Figure 7B is a schematic diagram showing the trajectory T of the center of the optical beam in the state shown in Figure 7A. Figure 8A is a schematic diagram showing an end-capped optical fiber 100 in a state where there is a misalignment in the central axis 70a of the fiber and the optical axis 70b of the lens due to the fusion of the optical fiber 10 and the end cap 20. Figure 8B is a schematic diagram showing the trajectory T of the center of the optical beam in the state shown in Figure 8A.

[0047] The end cap 20 shown in Figure 7A or Figure 8A has a shape in which the angles θ1 and θ2 described above change as the virtual plane P2 rotates once around the optical axis 70b of the lens. In contrast, the end cap 21 shown in Figure 1A or Figure 3A has a shape in which the angles θ1 and θ2 do not change as the virtual plane P2 rotates once around the optical axis 70b of the lens.

[0048] In the example shown in Figure 7A, the central axis 70a of the fiber and the optical axis 70b of the lens are coaxial, and there is no misalignment between the two axes. In this case, when the end cap 20 supported by the support member 42 is rotated 360° around the optical axis 70b of the lens, the position in which the end cap 20 is fixed to the support member 42 changes, as shown in Figures 5B and 6B, causing the end cap 20 to tilt. As a result, the trajectory T of the center of the optical axis 70c of the light beam is drawn in the upper first and second quadrants of the XY plane. In contrast, in the example shown in Figure 8A, there is a misalignment between the central axis 70a of the fiber and the optical axis 70b of the lens. In this case, when the end cap 20 is rotated 360° around the optical axis 70b of the lens, the position in which the end cap 20 is fixed to the support member 42 changes, as shown in Figures 5B and 6B, causing the end cap 20 to tilt. As a result, the trajectory T of the center of the optical axis 70c of the light beam is drawn in the lower third and fourth quadrants of the XY plane. Thus, in both cases where there is eccentricity between the fiber's central axis 70a and the lens's optical axis 70b, and where there is no eccentricity, the trajectory T does not necessarily pass through the origin of the XY plane, depending on the amount of eccentricity between the fiber's central axis 70a and the lens's optical axis 70b. However, the trajectory T is simply translated in the X or Y direction of the XY plane. Compared to the state in Figure 3A, there exists a rotation angle around the lens's optical axis 70b that allows a portion of the trajectory T to approach the origin of the XY plane. At this rotation angle, the angular misalignment between the lens's optical axis 70b and the optical axis 70c of the light beam on the XY plane, or the distance between the origin and the trajectory T, is minimized. Therefore, by fixing the end cap 20 at this rotation angle where the angular misalignment between the lens's optical axis 70b and the optical axis 70c of the light beam is minimized, it is possible to reduce the divergence angle of the collimated light beam.

[0049] Next, with reference to Figure 9, an example of the configuration of the optical fiber 10 included in the end capped optical fiber 100 according to this embodiment will be described. Figure 9 is a schematic diagram mainly showing an example of the configuration of the optical fiber 10. The area enclosed by the dashed line in Figure 9 represents the area where the intensity of the optical beam L is equal to or greater than its maximum intensity D4σ. D4σ is four times the standard deviation σ of the horizontal or vertical intensity distribution.

[0050] The optical fiber 10 comprises the following first part 10a and second part 10b. The first part 10a has a first core 10a1 and a first cladding 10a2 surrounding the first core 10a1. The refractive index of the first core 10a1 is higher than that of the first cladding 10a2. The second part 10b has a second core 10b1 and a second cladding 10b2 surrounding the second core 10b1. The refractive index of the second core 10b1 is higher than that of the second cladding 10b2. The second core 10b1 is adjacent to the first core 10a1, and the second cladding 10b2 is adjacent to the first cladding 10a2. The refractive index of the second core 10b1 is the same as that of the first core 10a1, and the refractive index of the second cladding 10b2 is the same as that of the first cladding 10a2. As the optical fiber 10, an optical fiber having a double-clad structure with other cladding on the outer periphery of the first cladding 10a2 and the outer periphery of the second cladding 10b2 may be used.

[0051] The dotted lines in Figure 9 represent the optical axis 70b of the lens and the optical axis 70c of the optical beam L. The optical axis 70c of the optical beam L may be shifted from the optical axis 70b of the lens due to the fusion of the optical fiber 10 and the end cap 20.

[0052] In the optical fiber 100 with an end cap according to this embodiment, the diameter of the first core 10a1 is constant along the central axis of the first core 10a1, and the diameter of the second core 10b1 is larger closer to the end cap 20. Furthermore, the focal point of the convex lens is located inside the optical fiber 10 and away from the end face of the second portion 10b. Therefore, the pseudo-emitting surface of the light propagating through the optical fiber 10 is located not at the end face 12 of the second portion 10b, but inside the second core 10b1 away from the end face 12, or at the boundary between the first core 10a1 and the second core 10b1.

[0053] The second core 10b1 may spread out in a curved shape as shown in Figure 9, or it may spread out in a straight line. When the second core 10b1 spreads out in a straight line, the radius of curvature of the side surface of the second core 10b1 may be, for example, 0.01 mm or more.

[0054] In the example shown in Figure 9, the shape of the spread of the second core 10b1 may be symmetrical with respect to the central axis of the second core 10b1. The length of the second portion 10b and the shape of the spread of the second core 10b1 depend on the splicing conditions, such as the heating temperature and pressure, when splicing the optical fiber 10 and the end cap 20.

[0055] The focal point F of the convex lens is located inside the optical fiber 10 and away from the end face 12 of the second portion 10b. More specifically, the focal point F of the convex lens is located inside the second core 10b1, or at the boundary between the first core 10a1 and the second core 10b1. The distance from the vertex of the convex lens to the focal point F is greater than the focal length f of this convex lens. Focal length refers to the rear focal length.

[0056] In the second section 10b, as the second core 10b1 expands toward the end face 12, the light beam guiding the optical fiber 10 also expands. Therefore, if the focal point F of the convex lens is set toward the end face of the second section 10b, the divergence angle of the collimated light beam increases. On the other hand, as shown in Figure 9, if the focal point F of the convex lens is located inside the optical fiber 10 and away from the end face 12 of the second section 10b, the divergence angle of the collimated light beam decreases. This holds true whether the divergence angle of the second core 10b1 is greater than or less than the critical angle of the first section 10a.

[0057] The end cap-equipped optical fiber 100 can also capture the collimated optical beam L from the second surface 22b of the end cap 20 and propagate it into the optical fiber 10. When the optical beam L is captured from the second surface 22b of the end cap 20, the above-mentioned pseudo-emitting surface is reinterpreted as a pseudo-receiving surface. In this way, the end cap-equipped optical fiber 100 makes it possible to effectively capture the collimated optical beam L from the end cap 20.

[0058] [Fiber Array] The fiber array according to this disclosure comprises a plurality of end-capped optical fibers, each of which is an end-capped optical fiber, and a support member that supports the outer peripheral surface of the end cap in each of the plurality of end-capped optical fibers, wherein the second surfaces of the end caps in each of the plurality of end-capped optical fibers face the same side, and the shortest distance from the connection point between the optical fiber and the end cap to the support member is different in at least two of the plurality of end-capped optical fibers.

[0059] In the fiber array of this disclosure configured as described above, the angular misalignment between the optical axis of the lens and the optical beam can be reduced by appropriately supporting the outer surface of the end cap of each end-capped optical fiber with a support member in accordance with the axial misalignment between the optical fiber and the end cap due to the fusion of the two. Furthermore, it becomes easier to improve the misalignment of the parallel optical axes between multiple end-capped optical fibers caused by manufacturing tolerances that may occur in the manufacturing process of a fiber array equipped with multiple end-capped optical fibers, and as a result, it becomes possible to reduce the optical utilization efficiency.

[0060] Below, an example of the configuration of a fiber array according to this embodiment will be described with reference to Figures 10 and 11. Figures 10 and 11 are schematic top view and front view, respectively, showing the configuration of a fiber array according to this embodiment.

[0061] The fiber array 200 in this embodiment comprises a plurality of end-capped optical fibers 100. In the example shown in Figures 10 and 11, there are three end-capped optical fibers 100, but the array is not limited to this example. The number of end-capped optical fibers 100 may be two or four or more.

[0062] The fiber array 200 includes a support member 42 that supports the outer circumferential surface 22c of each end cap 20 of a plurality of end cap optical fibers 100. The fiber array 200 further includes a fixing member 44 that sandwiches and fixes each of the end caps 20 of the plurality of end cap optical fibers 100 together with the support member 42, and a screw 46 that maintains the distance between the fixing member 44 and the support member 42. The fixing member 44 and the support member 42 are screwed together.

[0063] The support member 42 has a plurality of grooves 43. Each of the plurality of grooves 43 is, for example, a V-shaped groove. Each of the plurality of grooves 43 supports the outer surface of the end cap 20 included in the corresponding end cap optical fiber 100 among the plurality of end cap optical fibers 100.

[0064] The fiber array 200 in the example shown in Figures 10 and 11 further includes multiple screws 46 for securing multiple end-capped optical fibers 100 to a support member 42.

[0065] In multiple end-capped optical fibers 100, the second surfaces 22b of the end caps 20 face the same side. More specifically, in any two end-capped optical fibers 100, the angle formed by the optical axes of the lenses of the end caps 20 is 45° or less.

[0066] Due to manufacturing tolerances, misalignment of the parallel optical axes between multiple end-capped optical fibers 100 may occur. However, by rotating each end-capped optical fiber 100 around the optical axis of the lens and fixing it to the support member 42 in a state where the aforementioned angular misalignment is minimized, it becomes easier to improve the parallelism of the optical axes of the multiple light beams emitted from the multiple end-capped optical fibers 100.

[0067] Figure 11 shows the connection point 70 between the optical fiber 10 and the end cap 20, visible through the inside of each end cap 20. The central axis of the fiber is located at the connection point 70. Of the multiple end capped optical fibers 100, the shortest distance d from the connection point 70 between the optical fiber 10 and the end cap 20 to the support member 42 may differ in at least two of the end capped optical fibers 100. The shortest distance d is the shortest distance from the connection point 70 to the contact point between the outer surface of the end cap 20 and the groove 43.

[0068] In the manufacturing process of the fiber array, each of the multiple end-capped optical fibers 100 is fixed in the corresponding groove 43 of the multiple grooves 43 while rotating the end cap 20 around the optical axis as described above, so as to minimize the angular misalignment between the optical axis of the lens and the optical axis of the optical beam. As a result, the shortest distance d may differ between at least two end-capped optical fibers 100.

[0069] In the example shown in Figure 11, the shortest distances d1, d2, and d3 of the three end caps 20 are different from each other, and the three connection points 70 are not aligned in a straight line.

[0070] In this embodiment, the multiple end-capped optical fibers 100 are not fixed to the multiple grooves 43 of the support member 42 with adhesive. Instead, as shown in Figure 11, the multiple end-capped optical fibers 100 are fixed to the multiple grooves 43 of the support member 42 with screws 46. By fixing them with screws 46 instead of adhesive in this way, it becomes easier to fix the end-capped optical fibers 100 to or remove them from the support member 42. Furthermore, damage to the adhesive due to leaked light can be avoided. In particular, when connecting a high-power laser light source to a fiber array, it is often advantageous not to use adhesive to fix the end-capped optical fibers.

[0071] According to the fiber array 200 of this embodiment, it is possible to input light into multiple end-capped optical fibers 100 and emit multiple collimated light beams from the multiple end-capped optical fibers 100. Furthermore, it becomes easier to improve the misalignment of the parallel optical axes between the multiple end-capped optical fibers 100 due to manufacturing tolerances that may occur in the manufacturing process of the fiber array 200 equipped with multiple end-capped optical fibers 100, and as a result, it is possible to suppress a decrease in light utilization efficiency. The wavelengths of the light input into the multiple end-capped optical fibers 100 may all be the same, or some or all of them may be different.

[0072] [Light source device] A light source device according to one embodiment of the present disclosure comprises: a fiber array, wherein the plurality of end-capped optical fibers include a first end-capped optical fiber and a second end-capped optical fiber; a first laser light source that emits first laser light, wherein the first laser light is coupled to the optical fiber included in the first end-capped optical fiber from the side opposite to the end cap; and a second laser light source that emits second laser light, wherein the second laser light is coupled to the optical fiber included in the second end-capped optical fiber from the side opposite to the end cap.

[0073] In the light source device of this disclosure configured as described above, the divergence angle of the collimated light beam can be reduced and emitted for both the first laser beam and the second laser beam.

[0074] Next, an example of the configuration of the light source device according to this embodiment will be described with reference to Figure 12. Figure 12 is a schematic diagram showing the configuration of the light source device according to this embodiment. The light source device 300 shown in Figure 12 comprises a plurality of laser light sources 30 and a fiber array 200 having a plurality of end-capped optical fibers 100. Each end-capped optical fiber 100 corresponds to one laser light source 30. In Figure 12, the support member 42, fixing member 44, and screw 46 included in the fiber array 200 are omitted.

[0075] In the example shown in Figure 12, there are three laser light sources 30, but the example is not limited to this. The number of laser light sources 30 may be two or three or more. The number of end-capped optical fibers 100 is the same as the number of laser light sources 30.

[0076] The laser light emitted from each laser light source 30 is coupled to the optical fiber 10 contained in the corresponding end-capped optical fiber from the side opposite the end cap 20. As a result, each end-capped optical fiber 100 emits a collimated optical beam L from the second surface 22b of the end cap 20.

[0077] The peak wavelengths of the laser light emitted from multiple laser light sources 30 may all be the same, or some or all of them may be different. The optical fiber 10 and end cap 20 in each end capped optical fiber 100 are appropriately designed according to the peak wavelength of the laser light emitted from the corresponding laser light source 30.

[0078] The multiple laser light sources 30 include a first laser light source 30a that emits a first laser beam with a first peak wavelength, a second laser light source 30b that emits a second laser beam with a second peak wavelength, and a third laser light source 30c that emits a third laser beam with a third peak wavelength. These three peak wavelengths may be, for example, 200 nm to 1100 nm, preferably 240 nm to 700 nm, and more preferably 300 nm to 570 nm.

[0079] If the first peak wavelength, second peak wavelength, and third peak wavelength are the first wavelength λ1, second wavelength λ2, and third wavelength λ3 as described above, then the second peak wavelength is shorter than the first peak wavelength, and the third peak wavelength is shorter than the second peak wavelength.

[0080] The first laser beam is coupled to the optical fiber 10 contained in the first end-capped optical fiber 100A1 from the side opposite the end cap 20. The second laser beam is coupled to the optical fiber 10 contained in the second end-capped optical fiber 100A2 from the side opposite the end cap 20. The third laser beam is coupled to the optical fiber 10 contained in the third end-capped optical fiber 100A3 from the side opposite the end cap 20.

[0081] The first end cap optical fiber 100A1 emits a first optical beam La, collimated with the first laser beam, from the second surface 22b of the end cap 20. The second end cap optical fiber 100A2 emits a second optical beam Lb, collimated with the second laser beam, from the second surface 22b of the end cap 20. The third end cap optical fiber 100A3 emits a third optical beam Lc, collimated with the third laser beam, from the second surface 22b of the end cap 20. In Figure 12, the optical axes of each optical beam are shown by dashed lines. The optical axes of each optical beam are adjusted to be parallel to each other when viewed from above.

[0082] Based on the above, the light source device 300 according to this embodiment can emit multiple light beams from multiple laser light sources 30 via the fiber array 200, which are sufficiently collimated and have reduced divergence angles.

[0083] [Wavelength-beam coupling device] Next, with reference to Figure 13, an example of the configuration of a wavelength beam coupling device according to this embodiment will be described. A wavelength beam coupling device according to one embodiment of the present disclosure comprises the above-described light source device and a diffraction grating, wherein the first laser light has a first peak wavelength, the second laser light has a second peak wavelength shorter than the first peak wavelength, the first end cap optical fiber emits a first light beam collimated with the first laser light from the second surface of the end cap, the second end cap optical fiber emits a second light beam collimated with the second laser light from the second surface of the end cap, and the diffraction grating wavelength-combines the first light beam and the second light beam.

[0084] In the wavelength beam coupling apparatus of this disclosure configured as described above, a first light beam and a second light beam emitted from a light source device can be wavelength-combined by a diffraction grating to form a high-power coupled beam.

[0085] The wavelength beam coupling device comprises a light source device 300 that emits multiple optical beams L with different peak wavelengths, and a diffraction grating. The diffraction grating wavelength-combines multiple optical beams L, each including at least a first optical beam La with a first peak wavelength and a second optical beam Lb with a second peak wavelength shorter than the first peak wavelength. As a result, a high-power coupled beam is formed.

[0086] Figure 13 is a schematic diagram showing the configuration of the wavelength beam coupling apparatus according to this embodiment.

[0087] The wavelength beam coupling device 400 shown in Figure 13 comprises a light source device 300 that emits multiple unpolarized light beams L with different peak wavelengths, a first optical member 52a, a second optical member 52b, a first diffraction grating 53a, a second diffraction grating 53b, and an optical fiber 101 with an end cap. The first optical member 52a and the second optical member 52b have the same structure. The first diffraction grating 53a and the second diffraction grating 53b have the same structure and are arranged parallel to each other.

[0088] The unpolarized light beam L includes a first light beam La with a first peak wavelength, a second light beam Lb with a second peak wavelength, and a third light beam Lc with a third peak wavelength. The first, second, and third peak wavelengths are the first wavelength λ1, second wavelength λ2, and third wavelength λ3, respectively. That is, λ1 > λ2 > λ3.

[0089] The first optical member 52a includes a cube-shaped first polarizing beam splitter 52a1 having a first polarization plane 52as, a first prism 52a2, and a first polarization conversion element 52a3 which is a half-wave plate. The second optical member 52b includes a cube-shaped second polarizing beam splitter 52b1 having a second polarization plane 52bs, a second prism 52b2, and a second polarization conversion element 52b3 which is a half-wave plate.

[0090] In the example shown in Figure 13, the first polarizing beam splitter 52a1 and the first prism 52a2 are in contact, and the first prism 52a2 and the first polarization conversion element 52a3 are in contact, but the example is not limited to this. The first polarizing beam splitter 52a1 and the first prism 52a2 may be separated, and the first prism 52a2 and the first polarization conversion element 52a3 may be separated. The same applies to the second polarizing beam splitter 52b1 and the second prism 52b2, and the second prism 52b2 and the second polarization conversion element 52b3.

[0091] The double arrows in Figure 13 represent so-called P-polarization, where the polarization direction is parallel to the XZ plane, while the symbols enclosed in small circles in Figure 13 represent so-called S-polarization, where the polarization direction is perpendicular to the XZ plane. The solid lines in Figure 13 represent the unpolarized state, the dashed lines represent the S-polarized state, and the dashed-dotted lines represent the P-polarized state.

[0092] The first optical member 52a extracts multiple collimated S-polarized beams L1 and L2 propagating in the -X direction from multiple unpolarized light beams L propagating in the +Z direction, as follows. The reason for extracting multiple S-polarized beams L1 and L2 from multiple unpolarized light beams L is that the diffraction efficiency of S-polarized light is higher than that of P-polarized light in the first diffraction grating 53a and the second diffraction grating 53b.

[0093] In the first optical element 52a, the first polarization beam splitter 52a1 uses the first polarization plane 52as to separate a plurality of unpolarized light beams L traveling in the +Z direction into a plurality of S-polarized beams L1 traveling in the -X direction and a plurality of collimated P-polarized beams L3 traveling in the +Z direction. The first prism 52a2 performs total internal reflection of the plurality of P-polarized beams L3 traveling in the +Z direction in the -X direction. The first polarization conversion element 52a3 converts the plurality of P-polarized beams L3 into a plurality of S-polarized beams L2.

[0094] The first diffraction grating 53a is arranged so that multiple first polarized beams L1 and multiple second polarized beams L2 are all incident at an incident angle α (e.g., 45 degrees). The first diffraction grating 53a is further arranged so that multiple first polarized beams L1 incident parallel to each other at the same incident angle α are diffracted at different diffraction angles β1 to β3 according to their respective wavelengths λ1 to λ3, and incident into the first region 53b1 of the opposing second diffraction grating 53b. The first diffraction grating 53a is further arranged so that multiple second polarized beams L2 incident parallel to each other at the same incident angle α are diffracted at different diffraction angles β1 to β3 according to their respective wavelengths λ1 to λ3, and incident into the second region 53b2 of the opposing second diffraction grating 53b. The diffraction angle β2 corresponding to wavelength λ2 is smaller than the diffraction angle β1 corresponding to wavelength λ1, and the diffraction angle β3 corresponding to wavelength λ3 is smaller than the diffraction angle β2 corresponding to wavelength λ2. That is, β1 > β2 > β3.

[0095] The second diffraction grating 53b, having the same structure as the first diffraction grating 53a, is positioned to emit reflected diffracted light from the first diffraction grating 53a, which is incident at different incident angles β1 to β3 depending on the wavelength λ1 to λ3, at the same diffraction angle α (e.g., 45 degrees). As a result of the wavelength combination and coaxial coupling of multiple first polarization beams L1 in this manner, the first region 53b1 emits a collimated first combined beam CL1 of S polarization traveling in the -X direction. Similarly, as a result of the wavelength combination and coaxial coupling of multiple second polarization beams L2, the second region 53b2 emits a collimated second combined beam CL2 of S polarization traveling in the -X direction.

[0096] The second optical member 52b forms an unpolarized, collimated third coupled beam CL3 traveling in the +Z direction from a first coupled beam CL1 with S polarization traveling in the -X direction and a second coupled beam CL2 with S polarization traveling in the -X direction, as follows: In the second optical member 52b, the second polarization conversion element 52b3 converts the first coupled beam CL1 with S polarization into a collimated fourth coupled beam CL4 with P polarization. The second prism 52b2 totally reflects the fourth coupled beam CL4 traveling in the -X direction in the +Z direction. The second polarization beam splitter 52b1 uses the second polarization plane 52bs to polarize and combine the second coupled beam CL2 traveling in the -X direction and the fourth coupled beam CL4 traveling in the +Z direction to form an unpolarized third coupled beam L3 traveling in the +Z direction.

[0097] The end-capped optical fiber 101 effectively captures the unpolarized, collimated third coupled beam L3. The optical axis of the third coupled beam L3 is parallel to the optical axis of the lens contained in the end cap 20. The end-capped optical fiber 101 further emits the captured unpolarized third coupled beam L3 outside the wavelength beam coupling device 400. For example, an end-capped optical fiber 100 can be used as the end-capped optical fiber 101.

[0098] As described above, in the wavelength beam coupling device 400 of this embodiment, multiple collimated, unpolarized light beams L with different peak wavelengths are emitted from the light source device 300, and these multiple light beams L are wavelength-combined via the first optical member 52a, the first diffraction grating 53a, the second diffraction grating 53b, and the second optical member 52b in that order. As a result, an unpolarized, collimated, high-power third coupled beam L3 can be formed. The output of the third coupled beam L3 increases as the number of light beams L increases. The unpolarized, collimated third coupled beam L3 is effectively captured by the end-capped optical fiber 101 and emitted outside the wavelength beam coupling device 400.

[0099] This disclosure includes end-capped optical fibers, fiber arrays, light source devices, and wavelength beam coupling devices as described in the following items.

[0100] [Item 1] Optical fiber and An end cap having a first surface connected to the end face of the optical fiber, a second surface located on the opposite side of the first surface, and a side surface connecting the first surface and the second surface, Equipped with, The end cap includes a convex lens, The second surface includes a convex lens surface, The aforementioned side surface includes the outer surface surrounding the optical axis of the convex lens, An end-capped optical fiber, wherein the angle formed by each of the two intersecting lines between the virtual plane containing the optical axis and the outer surface with respect to the optical axis changes as the virtual plane rotates once around the optical axis.

[0101] [Item 2] The end capped optical fiber according to item 1, wherein the outer surface includes a region where the angle of one of the two intersecting lines is zero while the virtual plane rotates around the optical axis within a range of rotation angles.

[0102] [Item 3] An end capped optical fiber according to item 1 or 2, wherein the optical axis of the convex lens and the central axis of the optical fiber are misaligned.

[0103] [Item 4] The end cap optical fiber according to any one of items 1 to 3, wherein the outer surface includes a region in which the angle of one of the two intersecting lines changes in a range of 0.005° to 1° while the virtual plane rotates half a turn around the optical axis.

[0104] [Item 5] An end-capped optical fiber according to any one of items 1 to 4, wherein the two intersecting lines are nonparallel at a certain angle of rotation about the optical axis of the virtual plane.

[0105] [Item 6] The convex lens collimates and emits light propagating through the optical fiber, and is an end cap optical fiber according to any one of items 1 to 5.

[0106] [Item 7] The optical fiber is a multimode fiber, and is an end-capped optical fiber as described in any one of items 1 to 6.

[0107] [Item 8] Multiple end-capped optical fibers, each being an end-capped optical fiber described in any one of items 1 to 7, A support member that supports the outer circumferential surface of the end cap in each of the plurality of optical fibers with end caps, Equipped with, The second surfaces of the end caps in each of the plurality of end capped optical fibers face the same side. A fiber array in which, among the plurality of end-capped optical fibers, the shortest distance from the connection point between the optical fiber and the end cap to the support member is different for at least two of the end-capped optical fibers.

[0108] [Item 9] The support member has a plurality of grooves, The fiber array according to item 8, wherein each of the plurality of grooves supports the outer surface of the end cap included in the corresponding end cap optical fiber among the plurality of end cap optical fibers.

[0109] [Item 10] The system further comprises a fixing member that sandwiches and fixes each of the multiple end caps on the optical fibers with end caps together with the support member, The fixing member and the support member are fastened together with screws. The fiber array according to item 8 or 9, wherein the plurality of end-capped optical fibers are not fixed with adhesive to the plurality of grooves of the support member.

[0110] [Item 11] A fiber array according to any one of items 8 to 10, wherein the plurality of end-capped optical fibers include a first end-capped optical fiber and a second end-capped optical fiber, A first laser light source that emits a first laser beam, wherein the first laser beam is coupled to the optical fiber contained in the first end capped optical fiber from the side opposite to the end cap, A second laser light source that emits a second laser beam, wherein the second laser beam is coupled to the optical fiber contained in the second end capped optical fiber from the side opposite to the end cap, A light source device equipped with the following features.

[0111] [Item 12] A light source device as described in item 11, wherein the first laser light has a first peak wavelength and the second laser light has a second peak wavelength different from the first peak wavelength, Diffraction grating and, Equipped with, The optical fiber with the first end cap emits a first optical beam, which is collimated with the first laser light, from the second surface of the end cap. The optical fiber with the second end cap emits a second optical beam, in which the second laser light is collimated, from the second surface of the end cap. The diffraction grating is a wavelength beam coupling device that combines the wavelengths of the first light beam and the second light beam. [Industrial applicability]

[0112] The end-capped optical fibers, fiber arrays, light source devices, and wavelength beam coupling devices of this disclosure can be widely used in applications using collimated optical beams. [Explanation of symbols]

[0113] 10, 11: Optical fiber 10a: First part 10a1: First core 10a2: First cladding 10b: Second part 10b1: Second core 10b2: Second cladding 12: End face 20, 21: End cap 22a: First surface 22b: Second surface 22c: Outer surface: 22e, 22f: Region 25a, 25b: Crossing lines 30, 30a~30c: Laser light source 42: Support member 44: Fixing member 46: Screw 52a: First optical element 52a1: First polarizing beam splitter 52a2: First prism 52a3: First polarization conversion element 52as: First polarization plane 52b: Second optical element 52b1: Second polarizing beam splitter 52b2: Second prism 52b3: Second polarization conversion element 52bs: Second polarization plane 53a: First diffraction grating 53b: Second diffraction grating 53b1: First region 53b2: Second region 100, 101, 110, 111: Optical fibers with end caps 200: Fiber array 300: Light source device 400: Wavelength beam coupling device

Claims

1. Optical fiber and An end cap having a first surface connected to the end face of the optical fiber, a second surface located on the opposite side of the first surface, and a side surface connecting the first surface and the second surface, Equipped with, The end cap includes a convex lens, The second surface includes a convex lens surface, The aforementioned side surface includes the outer surface surrounding the optical axis of the convex lens, An end capped optical fiber, wherein the angle formed by each of the two intersecting lines between the virtual plane containing the optical axis and the outer surface with respect to the optical axis changes as the virtual plane rotates once around the optical axis.

2. The optical fiber with an end cap according to claim 1, wherein the outer surface includes a region where the angle of one of the two intersecting lines is zero while the virtual plane rotates around the optical axis within a range of rotation angles.

3. The optical fiber with an end cap according to claim 1 or 2, wherein the optical axis of the convex lens and the central axis of the optical fiber are misaligned.

4. The optical fiber with an end cap according to claim 1 or 2, wherein the outer surface includes a region in which the angle of one of the two intersecting lines changes in a range of 0.005° to 1° while the virtual plane rotates half a turn around the optical axis.

5. The optical fiber with an end cap according to claim 1 or 2, wherein the two intersecting lines are nonparallel at a certain angle of rotation about the optical axis of the virtual plane.

6. The optical fiber with an end cap according to claim 1 or 2, wherein the convex lens collimates and emits light propagating through the optical fiber.

7. The optical fiber with an end cap according to claim 1 or 2, wherein the optical fiber is a multimode fiber.

8. A plurality of end-capped optical fibers, each being an end-capped optical fiber according to claim 1 or 2, A support member that supports the outer circumferential surface of the end cap in each of the plurality of optical fibers with end caps, Equipped with, The second surfaces of the end caps in each of the plurality of end capped optical fibers face the same side. A fiber array in which, among the plurality of end-capped optical fibers, the shortest distance from the connection point between the optical fiber and the end cap to the support member is different for at least two of the end-capped optical fibers.

9. The support member has a plurality of grooves, The fiber array according to claim 8, wherein each of the plurality of grooves supports the outer surface of the end cap included in the end capped optical fiber among the plurality of end capped optical fibers.

10. The system further comprises a fixing member that sandwiches and fixes each of the multiple end caps on the optical fibers with end caps together with the support member, The fixing member and the support member are fastened together with screws. The fiber array according to claim 8, wherein the plurality of end capped optical fibers are not fixed with adhesive to the plurality of grooves of the support member.

11. A fiber array according to claim 8, wherein the plurality of end-capped optical fibers include a first end-capped optical fiber and a second end-capped optical fiber, A first laser light source that emits a first laser beam, wherein the first laser beam is coupled to the optical fiber contained in the first end capped optical fiber from the side opposite to the end cap, A second laser light source that emits a second laser beam, wherein the second laser beam is coupled to the optical fiber contained in the second end capped optical fiber from the side opposite to the end cap, A light source device equipped with the following features.

12. A light source device according to claim 11, wherein the first laser light has a first peak wavelength and the second laser light has a second peak wavelength different from the first peak wavelength, Diffraction grating and, Equipped with, The optical fiber with the first end cap emits a first optical beam, which is a collimated first laser beam, from the second surface of the end cap. The optical fiber with the second end cap emits a second optical beam, in which the second laser light is collimated, from the second surface of the end cap. The diffraction grating is a wavelength beam coupling device that wavelength-combines the first light beam and the second light beam.

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