JP2019179198A - Optical circulator and laser device - Google Patents

Abstract

To provide a downsizable optical circulator and a laser device.SOLUTION: Provided is an optical circulator 1 comprising: a first port 31, a second port 32 and a third port 33 which light from the outside enters; a first beam displacer 11, a second beam displacer 12 and a third beam displacer 13 constituted by birefringent crystal; and a Faraday rotator 21 and a polarization rotator 22 arranged between the first beam displacer 11 and the second beam displacer 12. The light entering from the first port 31 is emitted from the second port 32 after passing through the first beam displacer 11, the Faraday rotator 21, the polarization rotator 22 and the second beam displacer 12, the light entering from the second port 32 is emitted from the third port 33 after passing through the second beam displacer 12, the Faraday rotator 21, the polarization rotator 22, the first beam displacer 11 and the third beam displacer 13.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an optical circulator and a laser device, and more particularly to an optical circulator that can be miniaturized and a laser device including the optical circulator.

  Optical circulators are used in fields such as optical communication and optical measurement. An optical circulator is generally an element having three or four ports. For example, an optical circulator having three ports is generally configured such that light incident from the first port is emitted from the second port and light incident from the second port is emitted from the third port. . In an optical circulator having four ports, generally, light incident from the first port is emitted from the second port, light incident from the second port is emitted from the third port, and incident from the third port. The emitted light is emitted from the fourth port, and the light incident from the fourth port is emitted from the first port.

  In the following Patent Document 1, an example of a conventional optical circulator is described. This optical circulator includes a pair of cube-type polarizing beam splitters, a Faraday rotator and a half-wave plate disposed between these cube-type polarizing beam splitters, and a total reflection mirror.

JP 2002-31780 A

  In the conventional optical circulator described in Patent Document 1, a cube-type polarization beam splitter is used. However, a cube-type polarization beam splitter is generally composed of two prisms bonded together with an adhesive, and the adhesive absorbs light incident on the cube-type polarization beam splitter and generates heat. There is.

  On the other hand, when a cube-type polarizing beam splitter is manufactured by closely attaching two prisms without using an adhesive, the mechanical strength of the cube-type polarizing beam splitter tends to be low. In a cube-type polarizing beam splitter manufactured without using such an adhesive, it is preferable that two prisms having a certain size are brought into close contact with each other in order to ensure mechanical strength. However, as the polarizing beam splitter becomes larger, the expensive Faraday rotator or the like needs to be enlarged, and the optical circulator itself tends to increase in size. In addition, when downsizing a cube-type polarizing beam splitter manufactured without using an adhesive, the two prisms of a certain size are brought into close contact with each other as described above, and then the periphery of those prisms is shaved to make it smaller. There is a need to. However, if the periphery of the cube-type polarizing beam splitter is scraped, the outer peripheral portions of the joint surfaces of the two prisms tend to peel off from each other. Therefore, it is difficult to reduce the size of the cube-type polarizing beam splitter while securing a region for transmitting or reflecting light on the joint surface. Thus, it is difficult to reduce the size of a conventional optical circulator.

  Therefore, an object of the present invention is to provide an optical circulator and a laser device that can be miniaturized.

  An optical circulator according to the present invention for solving the above-described problems includes a first port through which light from the outside is incident, a first beam displacer configured by a birefringent crystal into which light from the first port is incident, A second beam displacer constituted by a birefringent crystal disposed on the opposite side of the first beam displacer from the first port side, and a Faraday rotation disposed between the first beam displacer and the second beam displacer. And a second port provided on the opposite side of the second beam displacer from the first beam displacer side, and on the opposite side of the first beam displacer from the second beam displacer side. A third beam displacer constituted by a birefringent crystal; and the third beam displacer. A third port provided on the opposite side of the placer from the first beam displacer side, wherein each polarized light incident on the first beam displacer from the first port is separated from the Faraday rotator and The polarization direction is rotated in the polarization rotator, is refracted in the second beam displacer so as to be at least partially overlapped with each other, is emitted from the second port, is incident on the second beam displacer from the second port, and is separated from each other. The polarized light is rotated in the polarization rotator and the Faraday rotator, further separated from each other in the first beam displacer, and refracted in the third beam displacer so as to at least partially overlap each other. Injection from 3 ports Characterized in that it is.

  The optical circulator does not need to use a cube-type polarizing beam splitter, and uses a beam displacer constituted by a birefringent crystal. Such a beam displacer can be easily downsized, and the Faraday rotator and the like can be downsized according to the size of the beam displacer. Therefore, the optical circulator can be miniaturized. Furthermore, since each beam displacer provided in the optical circulator can be configured without using an adhesive, heat generation by light incident on each beam displacer can be suppressed. Therefore, the optical circulator can cope with high-power light.

  In addition, when the polarized lights that are incident on the second beam displacer from the second port and are separated from each other pass through the first beam displacer, the distance between the polarized lights is transmitted through the third beam displacer. Is preferably substantially equal to the distance approached.

  Since the distance between the polarized lights separated from each other in the second beam displacer and the first beam displacer is equal to the distance in which the polarized lights are brought close to each other in the third beam displacer, the polarized lights are mutually separated in the third beam displacer. It becomes easy to overlap. Therefore, the beam diameter of the light emitted from the third port can be reduced, and the light can be easily emitted from the third port.

  The optical axis of the first beam displacer and the optical axis of the second beam displacer are parallel, and the optical axis of the third beam displacer and the optical axis of the first beam displacer are the first beam displacer and the optical axis of the first beam displacer. It is preferable to be symmetric with respect to a plane intermediate with the third beam displacer.

  The change in the distance between the respective polarizations propagating through the beam displacer can depend on the orientation of the optical axis of the beam displacer. By setting the orientation of the optical axis of each beam displacer as described above, the distance between the respective polarized light beams incident from the second port and separated from each other in the second beam displacer and the first beam displacer, and the third In the beam displacer, it becomes easy to make the distance at which these polarized lights come close to each other. Accordingly, the respective polarized lights incident from the second port and separated from each other in the second beam displacer and the first beam displacer are easily superimposed on each other in the third beam displacer. Therefore, the beam diameter of the light emitted from the third port can be reduced, and the light can be easily emitted from the third port.

  The total of the thickness of the first beam displacer and the thickness of the second beam displacer is preferably substantially equal to the thickness of the third beam displacer.

  The change in distance between the respective polarizations propagating through the beam displacer can also depend on the thickness of the beam displacer. By selecting the thickness of each beam displacer as described above, the distance between the polarized lights incident from the second port and separated from each other in the second beam displacer and the first beam displacer, and the third beam displacer. In this case, it becomes easy to make the distance at which these polarized lights come close to each other. Accordingly, the respective polarized lights incident from the second port and separated from each other in the second beam displacer and the first beam displacer are easily superimposed on each other in the third beam displacer. Therefore, the beam diameter of the light emitted from the third port can be reduced, and the light can be easily emitted from the third port.

  The thickness of the first beam displacer is preferably substantially equal to the thickness of the second beam displacer.

  It becomes easy to make the distance between the polarized lights incident from the first port and separated from each other in the first beam displacer equal to the distance between the polarized lights approaching each other in the second beam displacer. Therefore, the respective polarized lights incident from the first port and separated from each other in the first beam displacer are easily superimposed on each other in the second beam displacer. In addition, by selecting the thicknesses of the first beam displacer and the second beam displacer in this way, the first beam displacer and the second beam displacer can be configured by the same beam displacer. Therefore, the configuration of the optical circulator can be simplified. Furthermore, when the sum of the thickness of the first beam displacer and the thickness of the second beam displacer is the same as the thickness of the third beam displacer as described above, the same beam as the beam displacer constituting the first beam displacer. A third beam displacer can be constructed using two displacers. That is, the first beam displacer, the second beam displacer, and the third beam displacer can all be configured by the same beam displacer. Therefore, the configuration of the optical circulator can be simplified. However, even if the sum of the thickness of the first beam displacer and the thickness of the second beam displacer is the same as the thickness of the third beam displacer, the third beam displacer may be composed of one beam displacer. Good. In this case, the number of beam displacers to be used can be reduced as compared with the case where the third beam displacer is configured by two beam displacers as described above.

  In addition, it is preferable that at least one of the first port, the second port, and the third port has a mirror.

  By using the mirror, it becomes easy to guide light to a desired position, and the degree of freedom in designing the optical circulator can be improved.

  The mirror is provided adjacent to at least one of the first beam displacer, the second beam displacer, and the third beam displacer, and the mirror transmits the beam displacer adjacent to the mirror. It is preferably arranged between at least two polarized light paths.

  By arranging the mirror in this way, an extra space formed in the optical circulator can be utilized, and the optical circulator can be further downsized.

  Further, the fourth beam displacer constituted by a birefringent crystal disposed on the opposite side of the second beam displacer from the first beam displacer side is opposite to the second beam displacer side of the fourth beam displacer. A fourth port provided on the side, wherein each polarized light incident on the fourth beam displacer from the fourth port is separated from each other by entering the second beam displacer, and the Faraday It is preferable that the polarization direction is rotated in the rotator and the polarization rotator, and the first beam displacer is refracted so as to at least partially overlap with each other and is emitted from the first port.

  When the optical circulator includes the fourth port and the fourth beam displacer, a 4-port optical circulator in which light incident from the fourth port is emitted from the first port is obtained.

  Further, in the optical circulator including the fourth port and the fourth beam displacer, the respective polarized lights incident on the third beam displacer from the third port and separated from each other enter the first beam displacer and approach each other. The direction of polarization is rotated in the Faraday rotator and the polarization rotator, further separated from each other in the second beam displacer, and refracted so as to at least partially overlap with each other in the fourth beam displacer and emitted from the fourth port. It is preferred that

  By configuring the optical circulator in this manner, a 4-port optical circulator in which light incident from the third port is emitted from the fourth port is obtained.

  In addition, when the polarized lights that are incident on the fourth beam displacer from the fourth port and are separated from each other pass through the fourth beam displacer, the distances between the polarized lights are transmitted through the second beam displacer. It is preferable that the distances that are close to each other when the first polarized light is transmitted through the first beam displacer are substantially equal to the sum of the distances that are close to each other.

  Since the distance between the polarized lights separated from each other in the fourth beam displacer is equal to the distance between the polarized lights approaching each other in the second beam displacer and the first beam displacer, the polarized lights are easily overlapped with each other. Therefore, the beam diameter of the light emitted from the first port can be reduced, and the light can be easily emitted from the first port.

  The optical axis of the fourth beam displacer is preferably parallel to the optical axis of the third beam displacer.

  Each polarized light incident from the third port and separated from each other in the third beam displacer passes through the Faraday rotator and the polarization rotator and reaches the fourth beam displacer. Therefore, the polarized light that was ordinary light in the third beam displacer can be abnormal light in the fourth beam displacer, and the polarized light that was abnormal light in the third beam displacer can be ordinary light in the fourth beam displacer. That is, the polarized lights that are separated from each other in the third beam displacer are brought close to each other in the fourth beam displacer. Further, as described above, the change in the distance between the polarized lights propagating through the beam displacer can depend on the direction of the optical axis of the beam displacer. Since the optical axis of the third beam displacer and the optical axis of the fourth beam displacer are parallel to each other, the distance between the polarized lights separated from each other in the third beam displacer and the polarizations in the fourth beam displacer are It becomes easy to make the distances close to each other the same. Accordingly, the polarized lights incident from the third port and separated from each other in the third beam displacer are easily superimposed on each other in the fourth beam displacer. Therefore, the beam diameter of the light emitted from the fourth port can be reduced, and the light can be easily emitted from the fourth port.

  The total of the thickness of the first beam displacer and the thickness of the second beam displacer may be substantially equal to the thickness of the fourth beam displacer.

  As described above, the change in the distance between each polarized light propagating through the beam displacer can depend on the thickness of the beam displacer. Therefore, by selecting the thicknesses of the first beam displacer, the second beam displacer, and the fourth beam displacer as described above, the respective polarized lights incident from the fourth port and separated from each other in the fourth beam displacer are The second beam displacer and the first beam displacer can be easily overlapped with each other.

  The fourth port preferably has a mirror.

  By using the mirror, it becomes easy to guide light to a desired position, and the degree of freedom in designing the optical circulator can be improved.

  The mirror is preferably provided adjacent to the fourth beam displacer and disposed between at least two polarized light paths that pass through the fourth beam displacer.

  By arranging the mirror in this way, an extra space formed in the optical circulator can be utilized, and the optical circulator can be further downsized.

  In addition, a laser apparatus of the present invention for solving the above-described problems includes any one of the above-described first to third optical circulators and a signal light source that emits light incident on the first port of the optical circulator. And a first amplifier that amplifies the light emitted from the second port and enters at least a part of the amplified light into the second port, and the optical circulator is incident from the first port. The emitted light is emitted from the second port, and the light incident from the second port is emitted from the third port.

  Thus, the optical circulator of the present invention having the first to third ports can be applied to a laser device. The signal light is not limited to light including a signal.

  According to another aspect of the present invention, there is provided a laser apparatus comprising: an optical circulator having the first to fourth ports; a signal light source that emits light incident on the first port of the optical circulator; A first amplifier that amplifies the light emitted from the two ports and reflects at least part of the amplified light to the second port side; amplifies the light emitted from the third port; and the amplified light A second amplifier that reflects at least a part of the light to the third port side, and the optical circulator emits light incident from the first port from the second port and enters from the second port Light is emitted from the third port, and light incident from the third port is emitted from the fourth port.

  Thus, the optical circulator of the present invention having the first to fourth ports can be applied to a laser device.

  As described above, according to the present invention, an optical circulator and a laser device that can be miniaturized are provided.

1 is a diagram schematically showing a configuration of a laser device according to a first embodiment of the present invention. It is a figure which shows arrangement | positioning of the optical element in the optical circulator of 1st Embodiment of this invention, and the optical path of the light which injects from a 1st port. It is a figure which shows the optical path of the light which injects from the 2nd port of the optical circulator shown in FIG. It is a figure which shows the optical path of the light which injects from the 3rd port of the optical circulator shown in FIG. It is a figure which shows schematically the structure of the laser apparatus of 2nd Embodiment of this invention. It is a figure which shows arrangement | positioning of the optical element in the optical circulator of 2nd Embodiment of this invention, and the optical path of the light which injects from a 1st port. It is a figure which shows the optical path of the light which injects from the 2nd port of the optical circulator shown in FIG. It is a figure which shows the optical path of the light which injects from the 3rd port of the optical circulator shown in FIG. It is a figure which shows the optical path of the light which injects from the 4th port of the optical circulator shown in FIG.

  Hereinafter, embodiments of an optical circulator according to the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram schematically showing a configuration of a laser apparatus according to a first embodiment of the present invention. A laser apparatus 100 of the present embodiment shown in FIG. 1 includes a signal light source MO, the optical circulator 1 of the first embodiment, and a first amplifier AM1 as main components. The first amplifier AM1 includes a first collimating lens 3, an optical amplification glass body 4, a mirror 5, a second collimating lens 6, and an excitation light source 7 as main components.

  The signal light source MO is a light source that emits light incident on the optical circulator 1. The signal light source MO emits signal light that enters the first port 31 of the optical circulator 1 described later. The signal light source MO is made of, for example, a laser diode or a fiber laser. One end of a signal optical fiber 51 is connected to the signal light source MO. The signal light emitted from the signal light source MO propagates mainly through the core of the signal optical fiber 51 from one end of the signal optical fiber 51 to the other end.

  As described above, the signal light source MO is connected to one end of the signal optical fiber 51, and the optical circulator 1 is connected to the other end of the signal optical fiber 51.

  FIG. 2 is a diagram showing the arrangement of optical elements in the optical circulator according to the first embodiment of the present invention. As shown in FIG. 2, the optical circulator 1 of the present embodiment includes a housing 10, a first beam displacer 11, a second beam displacer 12, a third beam displacer 13, a Faraday rotator 21, a polarization rotator 22, and a first port. 31, a second port 32, and a third port 33 are provided as main components.

  The first port 31 is a part that guides light incident on one surface of the first beam displacer 11 from the outside of the optical circulator 1. The first port 31 of the present embodiment has a first opening 31h formed in the housing 10 and a first mirror 31m. For example, an optical fiber (not shown) is connected to the first opening 31h. The first mirror 31m of the present embodiment is a total reflection mirror, and light that enters the housing 10 from the first opening 31h is totally reflected by the first mirror 31m and is incident on one surface of the first beam displacer 11. To do.

  The first beam displacer 11 is arranged so that light from the first port 31 is incident on one surface, and is constituted by a parallel plate type birefringent crystal. Therefore, light incident on one surface of the first beam displacer 11 from the first port 31 is divided into S-polarized light that is ordinary light that follows Snell's law and P-polarized light that is abnormal light that does not follow Snell's law. . In the first beam displacer 11 of the present embodiment, light from the first port 31 is incident on one surface of the first beam displacer 11 perpendicularly. Each polarized light generated by the light incident on one surface of the first beam displacer 11 being separated in the first beam displacer 11 is parallel to the traveling direction of the light incident on the first beam displacer 11 and becomes the first beam displacer. 11 is emitted from the other surface.

  Further, the optical axis OA1 of the first beam displacer 11 of the present embodiment is such that extraordinary light is separated from ordinary light to the maximum when non-polarized light enters the first surface of the first beam displacer 11 perpendicularly from the first port 31. Is set to a possible angle. In addition, the thickness of the first beam displacer 11 of the present embodiment in the direction in which ordinary light propagates is such that ordinary light and extraordinary light are emitted when non-polarized light is incident on one surface of the first beam displacer 11 from the first port 31. It is set to a thickness that can be emitted from the other surface of the first beam displacer 11 with a sufficient separation. For example, the thickness of the first beam displacer 11 according to the present embodiment is such that when non-polarized light is incident on one surface of the first beam displacer 11 from the first port 31, the distance between ordinary light and extraordinary light is their beam diameter. Is set to a thickness that can be emitted from the other surface of the first beam displacer 11. By adjusting one or both of the orientation of the optical axis OA1 of the first beam displacer 11 and the thickness of the first beam displacer 11, the distance between the ordinary light and the abnormal light can be adjusted in the first beam displacer 11.

  The Faraday rotator 21 is disposed between the first beam displacer 11 and the second beam displacer 12. The light incident on the Faraday rotator 21 of the present embodiment from the first beam displacer 11 side is emitted to the second beam displacer 12 side with the polarization direction rotated 45 degrees clockwise as viewed along the traveling direction of the light. To do. On the other hand, the light incident on the Faraday rotator 21 of the present embodiment from the second beam displacer 12 side is rotated 45 degrees counterclockwise when viewed along the traveling direction of the light, and the first beam displacer 11 is rotated. To the side.

Examples of the material constituting the Faraday rotator 21 include terbium gallium garnet single crystal (TGG: Tb ₃ Ga ₅ O ₁₂ ), terbium aluminum garnet single crystal (TAG: Tb ₃ Al _5). O ₁₂ ), terbium, scandium, aluminum, garnet type single crystal (TSAG: Tb ₃ Sc ₂ Al ₃ O ₁₂ ), terbium, scandium, lutetium, aluminum, garnet type single crystal (TSLAG: Tb ₃ (Sc, Lu) ₂ Al ₃ O ₁₂ ) and the like.

  A magnetic application unit (not shown) is provided around the Faraday rotator 21, and a magnetic field having the first beam displacer 11 side of the Faraday rotator 21 as the N pole and the second beam displacer 12 side as the S pole is provided. Given. The Faraday rotator 21 rotates the polarization direction of the light as described above based on the magnetic field formed by the magnetic application unit. As a magnetic application part, magnets, such as a neodymium magnet, are mentioned, for example.

  The polarization rotator 22 is disposed between the first beam displacer 11 and the second beam displacer 12. The polarization rotator 22 of this embodiment is disposed between the first beam displacer 11 and the second beam displacer 12 on the second beam displacer 12 side with respect to the Faraday rotator 21. The light that enters the polarization rotator 22 of the present embodiment from the first beam displacer 11 side is emitted 45 degrees clockwise as viewed along the traveling direction of the light and the second beam displacer 12 side. . On the other hand, the light incident on the polarization rotator 22 of the present embodiment from the second beam displacer 12 side rotates 45 degrees clockwise as viewed in the traveling direction of the light and moves to the first beam displacer 11 side. Exit. Therefore, the polarization rotator 22 of the present embodiment emits the polarization direction of the light incident from the first beam displacer 11 side by rotating 45 degrees in the same direction as the rotation direction of the Faraday rotator 21. On the other hand, the polarization rotator 22 of the present embodiment emits the polarization direction of light incident from the second beam displacer 12 side by rotating it 45 degrees in the direction opposite to the rotation direction of the Faraday rotator 21. As such a polarization rotator 22 of this embodiment, for example, a half-wave plate or a quartz polarization axis rotator is used.

  The second beam displacer 12 is disposed on the opposite side of the first beam displacer 11 from the first port 31 side, and is composed of a parallel plate type birefringent crystal. The second beam displacer 12 of the present embodiment has the same configuration as the first beam displacer 11 and is arranged in parallel with the first beam displacer 11. That is, the optical axis OA2 of the second beam displacer 12 of this embodiment is parallel to the optical axis OA1 of the first beam displacer 11, and the thickness of the second beam displacer 12 of this embodiment is the same as that of the first beam displacer 11. Same as thickness. By adjusting one or both of the orientation of the optical axis OA2 of the second beam displacer 12 and the thickness of the second beam displacer 12, the distance between the ordinary light and the abnormal light can be adjusted in the second beam displacer 12.

  The second port 32 is provided on the opposite side of the second beam displacer 12 from the first beam displacer 11 side. The second port 32 of the present embodiment is an opening formed in the housing 10. One end of an optical fiber 52 is connected to the second port 32.

  The third beam displacer 13 is disposed on the opposite side of the first beam displacer 11 from the second beam displacer 12 side, and is constituted by a parallel plate type birefringent crystal. The third beam displacer 13 of this embodiment is disposed in parallel with the first beam displacer 11. In addition, the optical axis OA3 of the third beam displacer 13 and the optical axis OA1 of the first beam displacer 11 of this embodiment are symmetric with respect to an intermediate plane between the first beam displacer 11 and the third beam displacer 13. . Further, the thickness of the third beam displacer 13 of this embodiment is twice the thickness of the first beam displacer 11. By adjusting one or both of the direction of the optical axis OA3 of the third beam displacer 13 and the thickness of the third beam displacer 13, the distance between the ordinary light and the abnormal light can be adjusted in the third beam displacer 13.

  The third port 33 is provided on the opposite side of the third beam displacer 13 from the first beam displacer 11 side. The third port 33 of this embodiment is an opening formed in the housing 10. One end of a delivery fiber 53 is connected to the third port 33.

  The first collimating lens 3 shown in FIG. 1 is disposed between the other end of the optical fiber 52 and one end face of the optical amplification glass body 4. Light emitted from the other end of the optical fiber 52 is collimated by the first collimating lens 3 and enters one end face of the glass body 4 for light amplification. That is, the signal light emitted from the signal light source MO enters the optical circulator 2 from the first port 31 and exits from the second port 32, and passes through the optical fiber 52 and the first collimating lens 3 to obtain an optical amplification glass body. 4 is incident on one end face.

  An active element such as ytterbium (Yb) that is excited by the excitation light emitted from the excitation light source 7 is added to the glass body 4 for light amplification. Examples of such active elements include rare earth elements, and examples of rare earth elements include thulium (Tm), cerium (Ce), neodymium (Nd), europium (Eu), and erbium (Er) in addition to Yb. Can be mentioned. Furthermore, bismuth (Bi) etc. can be mentioned as an active element other than a rare earth element.

  The glass body 4 for optical amplification of this embodiment includes a cylindrical glass rod made of quartz to which the active element is added. The glass body for light amplification 4 of this embodiment has a coating layer made of resin or quartz having a lower refractive index than the glass rod surrounding the outer peripheral surface of the glass rod for the purpose of protecting the outer peripheral surface of the glass rod. You may do it. Examples of the resin constituting the coating layer include an ultraviolet curable resin, and the quartz constituting the coating layer includes, for example, a dopant such as fluorine (F) that lowers the refractive index so that the refractive index is lower than that of the glass rod. And quartz to which is added.

  The excitation light source 7 is provided on the side opposite to the optical amplification glass body 4 side of the mirror 5 and emits excitation light. The excitation light source 7 of this embodiment is composed of a plurality of laser diodes 71. In the present embodiment, the laser diode 71 is, for example, a Fabry-Perot type semiconductor laser made of a GaAs semiconductor, and emits excitation light having a center wavelength of 915 nm. Each laser diode 71 of the pumping light source 7 is connected to the pumping optical fiber 72, and pumping light emitted from the laser diode 71 propagates through the pumping optical fiber 72.

  Each pumping optical fiber 72 has one end connected to the laser diode 71 and the other end connected to one end of the optical combiner 73. An optical fiber 54 is connected to the other end of the optical combiner 73. Accordingly, the excitation light emitted from the excitation light source 7 enters one end of the optical fiber 54 via the excitation optical fiber 72 and the optical combiner 73.

  The second collimating lens 6 is disposed between the other end of the optical fiber 54 and the mirror 5. The excitation light emitted from the other end of the optical fiber 54 is collimated by the second collimating lens 6 and enters the mirror 5.

  The mirror 5 is provided between the optical amplification glass body 4 and the excitation light source 7 on the side opposite to the second port 32 side of the optical amplification glass body 4. The mirror 5 transmits at least part of the excitation light emitted from the excitation light source 7 to the glass body 4 for light amplification. That is, the mirror 5 transmits at least part of the excitation light emitted from the other end of the optical fiber 54 to the optical amplification glass body 4 side. The mirror 5 reflects at least a part of the signal light amplified by the optical amplification glass body 4 to the optical amplification glass body 4 side. Thus, the mirror 5 reflects light of a predetermined wavelength and transmits light of another predetermined wavelength. Such a mirror 5 of this embodiment is made of, for example, a dielectric multilayer film.

  Next, the operation of the laser apparatus 100 of this embodiment will be described.

  First, excitation light is emitted from each laser diode 71 of the excitation light source 7. This excitation light is incident on one end of the core of the optical fiber 54 via the excitation optical fiber 72 and the optical combiner 73 and propagates mainly through the core of the optical fiber 54. Excitation light emitted from the other end of the core of the optical fiber 54 is collimated by the second collimating lens 6, passes through the mirror 5, enters the optical amplification glass body 4, and propagates through the optical amplification glass body 4. The excitation light propagating through the optical amplification glass body 4 excites the active elements added to the optical amplification glass body 4.

  On the other hand, signal light is emitted from the signal light source MO. This signal light enters the optical circulator 1 from the first port 31 through the signal optical fiber 51.

  In FIG. 2, the path of light that enters the optical circulator 1 from the first port 31 is indicated by an arrow. In FIG. 2 and the following figures, the path of S-polarized light is indicated by a one-dot chain line, and the path of P-polarized light is indicated by a broken line. Further, in FIG. 2 and the following drawings, the polarization direction of light is indicated by an arrow surrounded by a circle. However, for ease of understanding, the polarization direction is shown by replacing the direction perpendicular to the paper with the left-right direction.

  As shown in FIG. 2, the light that enters the optical circulator 1 from the first port 31 enters the optical circulator 1 from the first opening 31 h, and is then totally reflected by the first mirror 31 m, so that the first beam displacer 11. Is incident on one of the surfaces. The light incident on one surface of the first beam displacer 11 is divided into S-polarized light, which is normal light polarized perpendicular to the first beam displacer 11, and P-polarized light, which is abnormal light. Light from the first port 31 enters perpendicularly to one surface of the first beam displacer 11, and ordinary light passes straight through the first beam displacer 11 and passes through the other surface of the first beam displacer 11. Exit. On the other hand, the abnormal light travels in the direction away from the ordinary light in the first beam displacer 11 and is transmitted, and is emitted from the other surface of the first beam displacer 11 so that the traveling direction is parallel to the ordinary light. Therefore, these ordinary light and extraordinary light propagate to the second beam displacer 12 with the mutual distance d1 being substantially constant.

  Each polarized light transmitted through the first beam displacer 11 enters the Faraday rotator 21. In the Faraday rotator 21, as described above, the polarization direction of the polarized light rotates 45 degrees clockwise as viewed along the traveling direction of the polarized light. Each polarized light transmitted through the Faraday rotator 21 enters the polarization rotator 22. In the polarization rotator 22, the polarization direction of the polarized light further rotates 45 ° clockwise as seen along the traveling direction of the polarized light as described above. Accordingly, the polarized light that has been S-polarized light in the first beam displacer 11 is transmitted through the Faraday rotator 21 and the polarization rotator 22 so that the polarization direction is rotated by 90 ° and becomes P-polarized light and enters the second beam displacer 12. . Further, the polarized light that was P-polarized light in the first beam displacer 11 is transmitted through the Faraday rotator 21 and the polarization rotator 22 so that the polarization direction is rotated by 90 ° and becomes S-polarized light and enters the second beam displacer 12. .

  The second beam displacer 12 has the same configuration as the first beam displacer 11 as described above, and is arranged in parallel to the first beam displacer 11. Therefore, the polarized light that was abnormal light in the first beam displacer 11 is rotated as the normal light in the second beam displacer 12 by rotating the polarization direction in the Faraday rotator 21 and the polarization rotator 22 as described above. Through. Further, the polarized light that was ordinary light in the first beam displacer 11 is changed into the abnormal light in the second beam displacer 12 by rotating the polarization direction in the Faraday rotator 21 and the polarization rotator 22 as described above. Like the extraordinary light in the beam displacer 11, it is refracted and transmitted. As a result, each polarized light incident on the surface of the second beam displacer 12 on the side of the first beam displacer 11 is overlapped and emitted on the surface of the second beam displacer 12 opposite to the side of the first beam displacer 11.

  The respective polarized lights that have passed through the second beam displacer 12 and overlapped with each other are emitted from the second port 32 to the outside of the optical circulator 1. As described above, the light that enters the optical circulator 1 from the first port 31 is emitted from the second port 32 to the outside of the optical circulator 1.

  The signal light emitted from the second port 32 enters from one end of the optical fiber 52 and exits from the other end, collimated by the first collimating lens 3, and enters one end face of the glass body 4 for light amplification. The signal light incident on one end face of the optical amplifying glass body 4 propagates through the optical amplifying glass body 4 to the other end face, and is amplified by stimulated emission of the active element in the excited state as described above. The signal light amplified in the optical amplification glass body 4 in this way is emitted from the other end face of the optical amplification glass body 4 and reflected by the mirror 5 toward the optical amplification glass body 4, and again the optical amplification glass. The light amplifying glass body 4 enters from the other end face of the body 4. Then, the signal light amplified as described above is further amplified in the optical amplification glass body 4 and emitted from one end face of the optical amplification glass body 4. As described above, the first amplifier AM1 amplifies the light emitted from the second port 32 and reflects at least a part of the amplified light to the second port 32 side.

  As described above, the signal light amplified by the optical amplification glass body 4 and emitted from one end face of the optical amplification glass body 4 is transmitted from the second port 32 through the first collimator lens 3 and the optical fiber 52. 1 is incident.

  FIG. 3 shows the arrangement of the optical elements in the optical circulator 1 of the present embodiment as in FIG. 2, and the optical path of the light that enters the optical circulator 1 from the second port 32 is indicated by an arrow.

  As shown in FIG. 3, the light that enters the optical circulator 1 from the second port 32 enters the optical circulator 1 from the second port 32, and then the first beam displacer 11 side of the second beam displacer 12. Incident on the opposite surface. In this way, the light incident on the second beam displacer 12 is divided into S-polarized light that is ordinary light and P-polarized light that is abnormal light in the second beam displacer 12. Light from the second port 32 is incident perpendicularly to the surface of the second beam displacer 12, and ordinary light passes straight through the second beam displacer 12 and is transmitted to the first beam displacer 11 side of the second beam displacer 12. The light is emitted from the surface. On the other hand, the abnormal light travels in the direction away from the ordinary light in the second beam displacer 12 and is transmitted, and is emitted from the surface of the second beam displacer 12 on the first beam displacer 11 side so that the traveling direction is parallel to the ordinary light. . Accordingly, the ordinary light and the extraordinary light propagate to the first beam displacer 11 with the mutual distance d2 being substantially constant. As described above, the first beam displacer 11 and the second beam displacer 12 of the present embodiment have the same configuration, and the distance d2 is the same as the distance d1.

  Each polarized light transmitted through the second beam displacer 12 enters the polarization rotator 22. In the polarization rotator 22, as described above, the polarization direction of the polarized light rotates 45 ° clockwise as viewed along the direction of travel of the polarized light. Each polarized light transmitted through the polarization rotator 22 enters the Faraday rotator 21. In the Faraday rotator 21, the polarization direction of the polarized light rotates 45 ° counterclockwise when viewed along the traveling direction of the polarized light as described above. Accordingly, the polarized light that has been S-polarized light in the second beam displacer 12 passes through the polarization rotator 22 and the Faraday rotator 21, and thus returns to the original polarization direction to become S-polarized light and enters the first beam displacer 11. Also, the polarized light that was P-polarized light in the second beam displacer 12 is transmitted through the polarization rotator 22 and the Faraday rotator 21, so that the polarization direction returns to the original state and becomes P-polarized light and enters the first beam displacer 11.

  The first beam displacer 11 has the same configuration as the second beam displacer 12 as described above, and is arranged in parallel to the second beam displacer 12. Therefore, the light that was ordinary light in the second beam displacer 12 is also transmitted to the first beam displacer 11 as ordinary light. In addition, the light that was abnormal light in the second beam displacer 12 becomes the abnormal light in the first beam displacer 11 and is refracted and transmitted in the same manner as the abnormal light in the second beam displacer 12. As a result, the polarized light incident on the surface of the first beam displacer 11 on the second beam displacer 12 side is mutually different on the surface opposite to the second beam displacer 12 side of the first beam displacer 11 than when incident. The distance d3 is increased and emitted. Since the first beam displacer 11 and the second beam displacer 12 of the present embodiment have the same configuration as described above, the distance d3 is twice the distance d2.

  The respective polarized light beams transmitted through the first beam displacer 11 propagate to the third beam displacer 13 with the mutual distance d3 being substantially constant, and enter the surface of the third beam displacer 13 on the first beam displacer 11 side. As described above, the optical axis OA3 of the third beam displacer 13 and the optical axis OA1 of the first beam displacer 11 of the present embodiment are relative to a plane intermediate between the first beam displacer 11 and the third beam displacer 13. Symmetric. Therefore, the propagation direction of extraordinary light in the third beam displacer 13 and the propagation direction of extraordinary light in the first beam displacer 11 are symmetric with respect to an intermediate plane between the first beam displacer 11 and the third beam displacer 13. . Accordingly, the extraordinary light incident on the surface of the third beam displacer 13 on the first beam displacer 11 side is refracted in a direction approaching the ordinary light and passes through the third beam displacer 13. Further, the thickness of the third beam displacer 13 of this embodiment is twice the thickness of the first beam displacer 11. Accordingly, the distance that the ordinary light and the extraordinary light approach each other while propagating through the third beam displacer 13 is equal to the distance d3 that is separated in the first beam displacer 11 and the second beam displacer 12. As a result, each polarized light incident on the surface of the third beam displacer 13 on the first beam displacer 11 side overlaps on the surface of the third beam displacer 13 opposite to the first beam displacer 11 side.

  The respective polarized lights that have passed through the third beam displacer 13 and overlapped with each other are emitted from the third port 33 to the outside of the optical circulator 1. As described above, light that enters the optical circulator 1 from the second port 32 is emitted from the third port 33 to the outside of the optical circulator 1.

  The light emitted from the third port 33 is incident on one end of the delivery fiber 53, is emitted from the other end of the delivery fiber 53, and is irradiated on the workpiece or the like.

  A part of the return light that is reflected by the surface of the object to be processed and returns to the delivery fiber 53 may enter the optical circulator 1 from the third port 33.

  FIG. 4 shows the arrangement of the optical elements in the optical circulator 1 of the present embodiment as in FIG. 2, and the optical path of the light incident from the third port 33 into the optical circulator 1 is indicated by an arrow.

  As shown in FIG. 4, the light that enters the optical circulator 1 from the third port 33 enters the optical circulator 1 from the third port 33, and then the first beam displacer 11 side of the third beam displacer 13. Incident on the opposite surface. In this way, the light incident on the third beam displacer 13 is divided into S-polarized light that is ordinary light and P-polarized light that is abnormal light in the third beam displacer 13. The light from the third port 33 is incident perpendicularly to the surface of the third beam displacer 13, and the ordinary light travels straight through the third beam displacer 13, and the first beam displacer 11 side of the third beam displacer 13. The light is emitted from the surface. On the other hand, the abnormal light travels in the direction away from the normal light in the third beam displacer 13 and is transmitted, and is emitted from the surface of the third beam displacer 13 on the first beam displacer 11 side so that the traveling direction is parallel to the normal light. .

  The respective polarized light beams transmitted through the third beam displacer 13 propagate to the first beam displacer 11 with the mutual distance d4 being substantially constant, and enter one surface of the first beam displacer 11. As described above, the optical axis OA3 of the third beam displacer 13 and the optical axis OA1 of the first beam displacer 11 of the present embodiment are relative to a plane intermediate between the first beam displacer 11 and the third beam displacer 13. Symmetric. Therefore, the propagation direction of extraordinary light in the third beam displacer 13 and the propagation direction of extraordinary light in the first beam displacer 11 are symmetric with respect to an intermediate plane between the first beam displacer 11 and the third beam displacer 13. . Therefore, the extraordinary light incident on one surface of the first beam displacer 11 is refracted in the direction approaching the ordinary light and passes through the first beam displacer 11. Further, the thickness of the first beam displacer 11 of this embodiment is ½ of the thickness of the third beam displacer 13. Therefore, the distance at which the extraordinary light and the ordinary light approach each other while propagating through the first beam displacer 11 is half of the distance d4 away from the third beam displacer 13. As a result, each polarized light incident on one surface of the first beam displacer 11 is emitted from the other surface of the first beam displacer 11 while being separated from each other by a distance d5 which is half of the distance d4.

  Each polarized light transmitted through the first beam displacer 11 enters the Faraday rotator 21. In the Faraday rotator 21, as described above, the polarization direction of the polarized light rotates 45 degrees clockwise as viewed along the traveling direction of the polarized light. Each polarized light transmitted through the Faraday rotator 21 enters the polarization rotator 22. In the polarization rotator 22, the polarization direction of the polarized light further rotates 45 ° clockwise as seen along the traveling direction of the polarized light as described above. Accordingly, the polarized light that has been S-polarized light in the first beam displacer 11 is transmitted through the Faraday rotator 21 and the polarization rotator 22 so that the polarization direction is rotated by 90 ° and becomes P-polarized light and enters the second beam displacer 12. . Further, the polarized light that was P-polarized light in the first beam displacer 11 is transmitted through the Faraday rotator 21 and the polarization rotator 22 so that the polarization direction is rotated by 90 ° and becomes S-polarized light and enters the second beam displacer 12. .

  The second beam displacer 12 has the same configuration as the first beam displacer 11 as described above, and is arranged in parallel to the first beam displacer 11. Therefore, the light that was abnormal light in the first beam displacer 11 goes straight through the second beam displacer 12 and is transmitted. In addition, the light that has been normal light in the first beam displacer 11 becomes abnormal light in the second beam displacer 12 and is refracted and transmitted in the same manner as the abnormal light in the first beam displacer 11. As a result, each polarized light incident on the surface of the second beam displacer 12 on the first beam displacer 11 side has a larger distance from each other on the surface of the second beam displacer 12 opposite to the first beam displacer 11 side. And then exit. The distance d6 between the polarized lights after passing through the second beam displacer 12 is the same as the distance d4.

  The polarized light beams that have passed through the second beam displacer 12 away from each other are irradiated on the inner surface of the housing 10 without reaching the second port 32. In addition, it is preferable that a light-absorbing member is disposed on a portion of the inner surface of the housing 10 that is irradiated with polarized light in this way. As described above, the light that enters the optical circulator 1 from the third port 33 is suppressed from being emitted outside the optical circulator 1. Therefore, even if the return light enters the optical circulator 1 from the third port 33, the return light can be suppressed from reaching the signal light source MO and the excitation light source 7.

  As described above, the optical circulator 1 of the present embodiment includes the first beam displacer configured by the first port 31, the second port 32, and the third port 33 into which light from the outside is incident and the birefringent crystal. 11, a second beam displacer 12 and a third beam displacer 13, and a Faraday rotator 21 and a polarization rotator 22 disposed between the first beam displacer 11 and the second beam displacer 12. In addition, the polarized light beams incident on the first beam displacer 11 from the first port 31 and separated from each other are refracted so that their polarization directions are rotated by the Faraday rotator 21 and the polarization rotator 22 and overlap each other in the second beam displacer 12. Then, the light is emitted from the second port 32. Further, the polarized light beams incident on the second beam displacer 12 through the second port 32 and separated from each other are further separated from each other in the first beam displacer 11 by rotating the polarization direction in the polarization rotator 22 and the Faraday rotator 21. The light beams are refracted so as to overlap each other in the third beam displacer 13 and are emitted from the third port 33.

  As described above, in the optical circulator 1 of the present embodiment, light incident from the first port 31 is emitted from the second port 32, and light incident from the second port 32 is emitted from the third port 33. Further, the optical circulator 1 of this embodiment does not need to use a cube-type polarization beam splitter, and uses a beam displacer constituted by a birefringent crystal. Such a beam displacer can be easily miniaturized, and the Faraday rotator 21 and the like can be miniaturized according to the size of the beam displacer. Therefore, the optical circulator 1 of the present embodiment can be reduced in size while the manufacturing cost can be suppressed. Furthermore, since each beam displacer provided in the optical circulator 1 of the present embodiment can be configured without using an adhesive, heat generation by light incident on each beam displacer can be suppressed. Therefore, each beam displacer provided in the optical circulator 1 of the present embodiment can cope with high output light. The high output light is, for example, light having an average output power or energy of 300 W or more. As described above, each beam displacer included in the optical circulator 1 can cope with high output light, so that the optical circulator 1 has, for example, a peak power of laser light emitted from the laser device 100 of 2 kW or more, preferably 7 kW or more. It can also be applied to Therefore, the optical circulator 1 can be applied to a processing laser device that outputs light to the outside of the laser device. For example, the wavelength of the laser beam emitted from the laser apparatus 100 to the outside is a single wavelength.

  Further, each beam displacer provided in the optical circulator 1 of the present embodiment corresponds to high output light as described above, thereby increasing the power density of light incident on each beam displacer and reducing the beam diameter of the light. Can be small. The smaller the beam diameter of the light incident on the beam displacer, the smaller the distance between the polarized light beams separated from each other in the beam displacer. For example, as shown in FIG. 4, in order to prevent light incident on the optical circulator 1 from the third port 33 from being emitted from the second port 32 to the outside of the optical circulator 1, the distance d6 is set to the second beam displacer 12. It is preferable that it is sufficiently large with respect to the beam diameter of each polarized light that passes through the beam. In order to make the distance d6 sufficiently large, it is preferable that the distances d4 and d5 are sufficiently large with respect to the beam diameter of the polarized light transmitted through each beam displacer. The distance d5 is preferably, for example, not less than twice the beam diameter of the polarized light transmitted through the first beam displacer 11. Thus, the preferred distance between the polarized light depends on the beam diameter of the polarized light. Therefore, the smaller the beam diameter of the polarized light, the smaller the distances d4, d5, d6 between the polarized light, and the smaller the beam displacer. By reducing the size of each beam displacer included in the optical circulator 1, the optical circulator 1 can be further reduced in size.

  Further, in the optical circulator 1 of the present embodiment, the total thickness of the first beam displacer 11 and the second beam displacer 12 is equal to the thickness of the third beam displacer 13. The change in the distance between the respective polarizations propagating through the beam displacer can depend on the thickness of the beam displacer. By selecting the thicknesses of the respective beam displacers as described above, the distance between the polarized lights incident from the second port 32 and separated from each other in the second beam displacer 12 and the first beam displacer 11, and the first In the three-beam displacer 13, it becomes easy to make the distance at which these polarized lights come close to each other. Therefore, the respective polarized lights incident from the second port 32 and separated from each other in the second beam displacer 12 and the first beam displacer 11 are easily superimposed on each other in the third beam displacer 13.

  Further, in the optical circulator 1 of the present embodiment, the respective distances d3 when the polarized lights that are incident on the second beam displacer 12 from the second port 32 and are separated from each other are transmitted through the first beam displacer 11, respectively. Are equal to the distance that can be brought close to each other when transmitted through the third beam displacer 13. The distance d3 between the polarized lights separated from each other in the second beam displacer 12 and the first beam displacer 11 and the distance in which the polarized lights are brought close to each other in the third beam displacer 13 are equal to each other. 13 are easily overlapped with each other. Therefore, the beam diameter of the light emitted from the third port 33 can be reduced, and the light can be easily emitted from the third port 33.

  Further, in the optical circulator 1 of the present embodiment, the thickness of the first beam displacer 11 and the thickness of the second beam displacer 12 are equal. Therefore, it becomes easy to make the distance between the polarized lights incident from the first port 31 and separated from each other in the first beam displacer 11 equal to the distance in which the polarized lights are brought close to each other in the second beam displacer 12. Therefore, the respective polarized lights incident from the first port 31 and separated from each other in the first beam displacer 11 are easily superimposed on each other in the second beam displacer 12. Further, by selecting the thicknesses of the first beam displacer 11 and the second beam displacer 12 in this way, the first beam displacer 11 and the second beam displacer 12 can be configured by the same beam displacer. Therefore, the configuration of the optical circulator 1 can be simplified. Furthermore, when the sum of the thickness of the first beam displacer 11 and the thickness of the second beam displacer 12 is the same as the thickness of the third beam displacer 13 as described above, the beam displacer constituting the first beam displacer 11 is used. The third beam displacer 13 can be configured by using two beam displacers similar to those in FIG. That is, the first beam displacer 11, the second beam displacer 12, and the third beam displacer 13 can all be constituted by the same beam displacer. Therefore, the configuration of the optical circulator 1 can be simplified. However, even if the sum of the thickness of the first beam displacer 11 and the thickness of the second beam displacer 12 is the same as the thickness of the third beam displacer 13, the third beam displacer 13 is a single beam displacer. It may be configured. In this case, the number of beam displacers to be used can be reduced as compared with the case where the third beam displacer 13 is configured by two beam displacers as described above.

  In the optical circulator 1 of the present embodiment, the first port 31 has the first mirror 31m. As described above, since at least one of the first port 31, the second port 32, and the third port 33 has the mirror, the light can be easily guided to a desired position, and the design flexibility of the optical circulator 1 can be improved. .

  The first mirror 31m is provided so as to be adjacent to the first beam displacer 11, and is disposed at a position sandwiched between the optical paths of the respective polarized light beams that are transmitted away from the first beam displacer 11. In this way, the mirror of any one of the ports is provided adjacent to any one of the beam displacers, and is sandwiched between the optical paths of the respective polarized light beams that are separated from each other and pass through the adjacent beam displacer. It is preferable to arrange | position. By arranging the mirror in this way, an extra space formed in the optical circulator 1 can be utilized, and the optical circulator 1 can be further downsized.

(Second Embodiment)
Next, a second embodiment of the present invention will be described in detail with reference to the drawings. In addition, about the component which is the same as that of 1st Embodiment, or equivalent, except the case where it demonstrates especially, the same referential mark is attached | subjected and the overlapping description is abbreviate | omitted.

  FIG. 5 is a diagram schematically showing a configuration of a laser apparatus according to the second embodiment of the present invention. The laser device 200 of this embodiment shown in FIG. 5 includes a signal light source MO, the optical circulator 2 of the second embodiment, a first amplifier AM1, and a second amplifier AM2 as main components. The optical circulator 2 is different in configuration from the optical circulator 1 of the first embodiment as described later. The second amplifier AM2 has the same configuration as the first amplifier AM1 except for the arrangement.

  FIG. 6 is a diagram showing an arrangement of optical elements in the optical circulator according to the second embodiment of the present invention. As shown in FIG. 6, the optical circulator 2 of this embodiment further includes a fourth beam displacer 14 and a fourth port 34, and the second port 32 has a second mirror 32m and a second opening 32h. Different from the optical circulator 1 of the first embodiment.

  The fourth beam displacer 14 is disposed on the opposite side of the second beam displacer 12 from the first beam displacer 11 side, and is constituted by a parallel plate type birefringent crystal. The fourth beam displacer 14 of the present embodiment has the same configuration as the third beam displacer 13 and is arranged in parallel with the third beam displacer 13. That is, the optical axis OA4 of the fourth beam displacer 14 of this embodiment is parallel to the optical axis OA3 of the third beam displacer 13, and the thickness of the fourth beam displacer 14 of this embodiment is the same as that of the third beam displacer 13. Same as thickness. That is, the sum of the thickness of the first beam displacer 11 and the thickness of the second beam displacer 12 is equal to the thickness of the fourth beam displacer 14. By adjusting one or both of the optical axis OA4 of the fourth beam displacer 14 and the thickness of the fourth beam displacer 14, the distance between the ordinary light and the abnormal light can be adjusted in the fourth beam displacer 14.

  The fourth port 34 is provided on the side opposite to the second beam displacer 12 side of the fourth beam displacer 14. The fourth port 34 of the present embodiment is an opening formed in the housing 10. One end of a delivery fiber 53 is connected to the fourth port 34.

  The second port 32 of the present embodiment has a second opening 32h formed in the housing 10 and a second mirror 32m. One end of the optical fiber 52 is connected to the second opening 32h. The second mirror 32m of the present embodiment is a total reflection mirror, and light that enters the housing 10 from the second opening 32h is totally reflected by the second mirror 32m, and the first beam displacer 11 of the second beam displacer 12 is reflected. Incident on the surface opposite to the side.

  In addition, one end of the optical fiber 55 is connected to the third port 33 of the present embodiment. The optical fiber 55 is an optical fiber having the same structure as the optical fiber 52.

  Next, the operation of the laser device 200 of this embodiment will be described.

  First, similarly to the laser device 100 of the first embodiment, excitation light is emitted from the respective laser diodes 71 of the excitation light source 7 of the first amplifier AM1, and the excitation light is light amplification glass of the first amplifier AM1. It propagates through the body 4 to excite the active element added to the light amplification glass body 4. In addition, excitation light is also emitted from the respective laser diodes 71 of the excitation light source 7 of the second amplifier AM2, and the excitation light propagates through the optical amplification glass body 4 of the second amplifier AM2 and the optical amplification glass body. The active element added to 4 is excited.

  On the other hand, signal light is emitted from the signal light source MO, and the signal light enters the optical circulator 1 from the first port 31 through the signal optical fiber 51.

  FIG. 6 shows an optical path of light that enters the optical circulator 2 from the first port 31 in the optical circulator 2 with an arrow.

  As shown in FIG. 6, the path of light entering the optical circulator 2 from the first port 31 is the same as that of the optical circulator 1 of the first embodiment until it passes through the second beam displacer 12. The respective polarized lights that have passed through the second beam displacer 12 and overlapped with each other are totally reflected by the second mirror 32m and are emitted from the second opening 32h to the outside of the optical circulator 2. As described above, the light that enters the optical circulator 1 from the first port 31 is emitted from the second port 32 to the outside of the optical circulator 2.

  Similarly to the laser device 100 of the first embodiment, the signal light emitted from the second port 32 propagates through the optical amplifying glass body 4 and is amplified, and enters the optical circulator 2 again from the second port 32.

  FIG. 7 shows the arrangement of the optical elements in the optical circulator 2 of the present embodiment as in FIG. 6, and the optical path of light that enters the optical circulator 2 from the second port 32 is indicated by an arrow.

  As shown in FIG. 7, the light that enters the optical circulator 2 from the second port 32 enters the optical circulator 2 through the second opening 32 h, and then is totally reflected by the second mirror 32 m, and the second beam displacer 12. Is incident on the surface opposite to the first beam displacer 11 side. The subsequent light path is the same as that after the light from the second port 32 enters the second beam displacer 12 in the optical circulator 1 of the first embodiment. As described above, the light that enters the optical circulator 2 from the second port 32 is emitted from the third port 33 to the outside of the optical circulator 2.

  Light emitted from the third port 33 enters from one end of the optical fiber 55, exits from the other end, and enters the second amplifier AM2. Similar to the first amplifier AM1, the second amplifier AM2 amplifies the incident light and reflects at least a part of the amplified light to the incident side. That is, the second amplifier AM2 amplifies the light emitted from the third port 33, and reflects at least a part of the amplified light to the third port 33 side. Thus, the light reflected by the second amplifier AM2 enters the optical circulator 2 again from the third port 33.

  FIG. 8 shows the arrangement of the optical elements in the optical circulator 2 of the present embodiment as in FIG. 6, and the optical path of the light that enters the optical circulator 2 from the third port 33 is indicated by an arrow.

  As shown in FIG. 8, the path of light entering the optical circulator 2 from the third port 33 is the same as that of the optical circulator 1 of the first embodiment until it passes through the second beam displacer 12. Each polarized light transmitted through the second beam displacer 12 propagates to the fourth beam displacer 14 with the mutual distance d6 being substantially constant, and enters the surface of the fourth beam displacer 14 on the second beam displacer 12 side. The fourth beam displacer 14 has the same configuration as the third beam displacer 13 as described above, and is arranged in parallel to the third beam displacer 13. Therefore, the light that was abnormal light in the third beam displacer 13 becomes normal light in the fourth beam displacer 14 and passes straight. In addition, the light that has been ordinary light in the third beam displacer 13 becomes abnormal light in the fourth beam displacer 14 and is refracted and transmitted in the same manner as the abnormal light in the third beam displacer 13. As a result, each polarized light incident on one surface of the fourth beam displacer 14 overlaps on the other surface of the fourth beam displacer 14 and is emitted.

  The respective polarized lights that have passed through the fourth beam displacer 14 and overlapped with each other are emitted from the fourth port 34 to the outside of the optical circulator 2. As described above, the light that enters the optical circulator 2 from the third port 33 is emitted from the fourth port 34 to the outside of the optical circulator 2.

  The light emitted from the fourth port 34 is incident on one end of the delivery fiber 53, is emitted from the other end of the delivery fiber 53, and is irradiated on the workpiece or the like.

  Note that part of the return light that is reflected by the surface of the object to be processed and returns to the delivery fiber 53 may enter the optical circulator 2 from the fourth port 34.

  FIG. 9 shows the arrangement of the optical elements in the optical circulator 2 of the present embodiment as in FIG. 6, and the optical path of light that enters the optical circulator 2 from the fourth port 34 is indicated by arrows.

  As shown in FIG. 9, the light that enters the optical circulator 2 from the fourth port 34 enters the optical circulator 2 from the fourth port 34, and then is the second beam displacer 12 side of the fourth beam displacer 14. Incident on the opposite surface. Thus, the light incident on the fourth beam displacer 14 is divided into S-polarized light that is ordinary light and P-polarized light that is abnormal light in the fourth beam displacer 14. Light from the fourth port 34 enters perpendicularly to the surface of the fourth beam displacer 14 opposite to the second beam displacer 12 side, and ordinary light passes straight through the fourth beam displacer 14 and passes through the fourth beam displacer 14. The light is emitted from the surface of the 4-beam displacer 14 on the second beam displacer 12 side. On the other hand, the abnormal light travels in the direction away from the ordinary light in the fourth beam displacer 14 and is transmitted, and is emitted from the surface of the fourth beam displacer 14 on the second beam displacer 12 side so that the traveling direction is parallel to the ordinary light. .

  Each polarized light transmitted through the fourth beam displacer 14 propagates to the second beam displacer 12 with the mutual distance d7 being substantially constant, and on the surface of the second beam displacer 12 opposite to the first beam displacer 11 side. Incident. The optical axis OA2 of the second beam displacer 12 and the optical axis OA4 of the fourth beam displacer 14 of this embodiment are symmetric with respect to a plane intermediate between the second beam displacer 12 and the fourth beam displacer 14. Therefore, the propagation direction of extraordinary light in the second beam displacer 12 and the propagation direction of extraordinary light in the fourth beam displacer 14 are symmetric with respect to an intermediate plane between the second beam displacer 12 and the fourth beam displacer 14. . Therefore, the abnormal light incident on the second beam displacer 12 from the fourth beam displacer 14 side is refracted in a direction approaching the ordinary light and passes through the second beam displacer 12. Further, the thickness of the second beam displacer 12 of the present embodiment is ½ of the thickness of the fourth beam displacer 14. Accordingly, the distance at which the extraordinary light and the ordinary light approach each other while propagating through the second beam displacer 12 is half of the distance d7 at which the respective polarized lights are separated from each other in the fourth beam displacer 14. As a result, the polarized light incident on the surface opposite to the first beam displacer 11 side of the second beam displacer 12 is separated from each other by a distance d8 which is half the distance d7, and is a surface on the first beam displacer 11 side. Emanates from.

  Each polarized light transmitted through the second beam displacer 12 enters the polarization rotator 22. In the polarization rotator 22, as described above, the polarization direction of the polarized light rotates 45 ° clockwise as viewed along the direction of travel of the polarized light. Each polarized light transmitted through the polarization rotator 22 enters the Faraday rotator 21. In the Faraday rotator 21, as described above, the polarization direction of the polarized light rotates 45 ° counterclockwise when viewed along the traveling direction of the polarized light. Accordingly, the polarized light that has been S-polarized light in the second beam displacer 12 passes through the polarization rotator 22 and the Faraday rotator 21, and thus returns to the original polarization direction to become S-polarized light and enters the first beam displacer 11. Also, the polarized light that was P-polarized light in the second beam displacer 12 is transmitted through the polarization rotator 22 and the Faraday rotator 21, so that the polarization direction returns to the original state and becomes P-polarized light and enters the first beam displacer 11.

  The first beam displacer 11 has the same configuration as the second beam displacer 12 as described above, and is arranged in parallel to the second beam displacer 12. Therefore, the light that was ordinary light in the second beam displacer 12 is also transmitted to the first beam displacer 11 as ordinary light. Further, the light that is abnormal light in the second beam displacer 12 becomes refracted light in the first beam displacer 11 and is refracted and transmitted in the same manner as the abnormal light in the second beam displacer 12. As a result, the polarized light incident on the surface of the first beam displacer 11 on the second beam displacer 12 side is mutually different on the surface opposite to the second beam displacer 12 side of the first beam displacer 11 than when incident. The distance becomes smaller and emitted. Note that the total thickness of the first beam displacer 11 and the second beam displacer 12 in this embodiment is the same as the thickness of the fourth beam displacer 14. Therefore, in the fourth beam displacer 14, the distance d 7 where the respective polarizations are separated from each other, the distance where the respective polarizations approach each other while propagating through the second beam displacer 12, and the respective polarizations while propagating through the first beam displacer 11. The sum of the distances approaching each other is the same. Accordingly, each polarized light incident on the surface of the first beam displacer 11 on the second beam displacer 12 side is overlapped and emitted on the surface of the first beam displacer 11 opposite to the second beam displacer 12 side.

  The respective polarized lights that have passed through the first beam displacer 11 and overlapped with each other are totally reflected by the first mirror 31m, and are emitted from the first opening 31h to the outside of the optical circulator 2. As described above, light that enters the optical circulator 2 from the fourth port 34 is emitted from the first port 31 to the outside of the optical circulator 2.

  From the viewpoint of suppressing the light emitted from the first port 31 to the outside of the optical circulator 2 from entering the signal light source MO as described above, between the signal light source MO and the first port 31 of the optical circulator 2, It is preferable to arrange an isolator (not shown).

  As described above, in the laser apparatus 200 of the present embodiment, the signal light emitted from the signal light source MO is amplified in the optical amplification glass body 4 of the first amplifier AM1, and then is used for optical amplification of the second amplifier AM2. It is further amplified in the glass body 4.

  Further, the optical circulator 2 of the present embodiment includes a fourth beam 34 constituted by a fourth port 34 through which light from the outside is incident and a birefringent crystal through which light incident from the fourth port 34 into the optical circulator 2 is incident. A displacer 14. Further, in the optical circulator 2 of the present embodiment, the respective polarized lights that are incident on the fourth beam displacer 14 from the fourth port 34 and are separated from each other are incident on the second beam displacer 12 and brought close to each other, and the Faraday rotator 21. The polarization direction is rotated by the polarization rotator 22, and the first beam displacer 11 is refracted so as to overlap with each other and is emitted from the first port 31. By providing the optical circulator 2 with the fourth port 34 and the fourth beam displacer 14 as described above, a 4-port optical circulator 2 in which light incident from the fourth port 34 is emitted from the first port 31 is obtained. .

  Further, in the optical circulator 2 of the present embodiment, the respective polarized lights that are incident on the third beam displacer 13 from the third port 33 and are separated from each other are incident on the first beam displacer 11 to be close to each other, and the Faraday rotator 21. The polarization direction is rotated in the polarization rotator 22, further separated from each other in the second beam displacer 12, and refracted so as to at least partially overlap with each other in the fourth beam displacer 14, and emitted from the fourth port 34. By configuring the optical circulator 2 in this way, the 4-port optical circulator 2 in which the light incident from the third port 33 is emitted from the fourth port 34 is obtained as described above.

  Further, in the optical circulator 2 of the present embodiment, the respective distances d7 when the respective polarized lights incident on the fourth beam displacer 14 from the fourth port 34 and transmitted through the fourth beam displacer 14 are transmitted through the fourth beam displacer 14, respectively. Are equal to the sum of the distances that are close to each other when transmitted through the second beam displacer 12 and the distances that are approached to each other when the respective polarized light is transmitted through the first beam displacer 11. The distance d7 between the polarized lights separated from each other in the fourth beam displacer 14 is equal to the distance in which the polarized lights are brought close to each other in the second beam displacer 12 and the first beam displacer 11, so that the polarized lights overlap each other. It becomes easy to be done. Therefore, the beam diameter of the light emitted from the first port 31 can be reduced, and the light can be easily emitted from the first port 31.

  Further, in the optical circulator 2 of the present embodiment, the sum of the thickness of the first beam displacer 11 and the thickness of the second beam displacer 12 is equal to the thickness of the fourth beam displacer 14. As described above, the change in the distance between each polarized light propagating through the beam displacer can depend on the thickness of the beam displacer. Therefore, by selecting the thicknesses of the first beam displacer 11, the second beam displacer 12 and the fourth beam displacer 14 as described above, they are incident from the fourth port 34 and are separated from each other in the fourth beam displacer 14. The respective polarized lights are easily transmitted through the second beam displacer 12 and the first beam displacer 11 and overlap each other.

  Although the present invention has been described above by taking the embodiments as examples, the present invention is not limited to these embodiments.

  For example, the directions and thicknesses of the optical axes of the first beam displacer 11, the second beam displacer 12, the third beam displacer 13, and the fourth beam displacer 14 will be described in the description of the first and second embodiments. It is not limited to the illustrated form. For example, in the first embodiment, the first beam displacer 11 and the first beam displacer 11 and the second beam displacer 12 in a range where the respective polarized lights incident on the first beam displacer 11 and separated from each other at least partially overlap each other in the first port 31. The direction and thickness of the optical axis of the second beam displacer 12 can be adjusted as appropriate. Further, the direction and thickness of the optical axis of the third beam displacer 13 are separated from each other by being incident on the second beam displacer 12 from the second port 32, and the respective polarized lights that are further separated from each other in the first beam displacer 11. The three-beam displacer 13 can be appropriately adjusted within a range at least partially overlapping each other. In the second embodiment, the direction and thickness of the optical axis of the fourth beam displacer 14 is such that the respective polarized lights incident on the fourth beam displacer 14 from the fourth port 34 and separated from each other are the second beam displacer 12. The first beam displacer 11 can be adjusted as appropriate within a range where the first beam displacer 11 and at least partially overlap each other.

  Further, in the above-described embodiment, an example in which each beam displacer is configured by a parallel plate type birefringent crystal has been described. However, the shape of each beam displacer is not limited to this. For example, the cross-sectional shape of each beam displacer may be a wedge-shaped entrance surface and an exit surface that are not parallel to each other, or may be a parallelogram other than a rectangle.

  Further, in the above-described embodiment, the light incident on each beam displacer has been described by taking an example in which the light is incident perpendicular to the surface of the beam displacer. However, light may be incident non-perpendicularly on the surface of each beam displacer. For example, from the viewpoint of suppressing reflection of light emitted from the beam displacer, even if the shape or arrangement of each beam displacer is different from the above embodiment so that light is incident on the beam displacer at a predetermined angle. Good.

  Further, the position of the mirror is not particularly limited. Therefore, any of the first port 31, the second port 32, the third port 33, and the fourth port 34 may have a mirror. However, when a mirror is provided, the mirror is preferably provided adjacent to at least one of the first beam displacer 11, the second beam displacer 12, the third beam displacer 13, and the fourth beam displacer 14. The mirror is preferably disposed between at least two polarized light paths that pass through the beam displacer adjacent to the mirror. Note that the mirror may not be provided. When the port does not have a mirror, an optical fiber or the like may be provided in the port, and light may be guided to the beam displacer by the optical fiber. For example, when the first port 31 does not have the first mirror 31m, the first port 31 has an optical fiber that guides the light emitted from the signal light source MO from the first opening 31h to one surface of the first beam displacer 11. Is preferred. In this case, light incident from the first opening 31 h propagates through the optical fiber and is guided to one surface of the first beam displacer 11.

  In the above embodiment, an example in which the mirror included in the port of the optical circulator is a total reflection mirror has been described. However, when the port of the optical circulator has a mirror, the mirror may be a partially reflecting mirror that reflects a part of the incident light and transmits the other part. For example, the mirror included in the port of the optical circulator is a partially reflecting mirror that transmits incident light by about 0.1%. Thus, when the port of the optical circulator has a partial reflection mirror, the power of the light incident on the optical circulator can be indirectly observed by observing the light transmitted through the partial reflection mirror. For example, when the first mirror 31m of the first embodiment is a partial reflection mirror, part of the light incident on the optical circulator 1 from the first opening 31h is transmitted through the first mirror 31m. Thus, the light transmitted through the first mirror 31m is guided to the inner surface of the casing 10 opposite to the first opening 31h with the first mirror 31m interposed therebetween. Thus, by arranging a photodiode or the like having a light receiving surface at a position where the light transmitted through the first mirror 31m reaches, the power of light incident on the optical circulator 1 from the first opening 31h is indirectly observed. be able to.

  Moreover, in the said embodiment, the excitation light entered and demonstrated the example which injects into the glass body 4 for optical amplification from the opposite side to signal light. However, the excitation light source may be configured such that the excitation light enters the optical amplification glass body 4 from the same side as the signal light.

  In the above-described embodiment, the first amplifier AM1 and the second amplifier AM2 have been described with examples having the same configuration. However, the first amplifier AM1 and the second amplifier AM2 may have different configurations. . In the above-described embodiment, the first amplifier AM1 and the second amplifier AM2 have been described as having the configuration in which the signal light is reflected by the mirror 5. However, the first amplifier AM1 and the second amplifier AM2 may not be of the reflective type.

Note that the optical circulator of the present invention is not limited to the use examples shown in the above-described embodiment, and is also used for, for example, a reflected light monitor, oscillation wavelength lock, guide light multiplexing, and the like. Further, when the optical circulator of the present invention is used in a laser device, the laser device is not limited to a MOPA type fiber laser device. For example, a CW (continuous oscillation) type, CO ₂ (carbon dioxide) laser, YAG laser, etc. Other laser devices may be used.

  As described above, according to the present invention, an optical circulator that can be miniaturized is provided, and used in fields such as a fiber laser device, optical communication, and optical measurement for high output.

1, 2 ... Optical circulator 10 ... Housing 11 ... First beam displacer 12 ... Second beam displacer 13 ... Third beam displacer 14 ... Fourth beam displacer 21 ... Faraday rotator 22 ... polarization rotator 31 ... first port 31h ... first opening 31m ... first mirror 32 ... second port 32h ... second opening 32m ... second Mirror 33 ... third port 34 ... fourth port 100, 200 ... laser device MO ... signal light source AM1 ... first amplifier AM2 ... second amplifier

Claims (16)

A first port through which light from the outside is incident;
A first beam displacer constituted by a birefringent crystal into which light from the first port is incident;
A second beam displacer constituted by a birefringent crystal disposed on the side opposite to the first port side of the first beam displacer;
A Faraday rotator and a polarization rotator disposed between the first beam displacer and the second beam displacer;
A second port provided on the opposite side of the second beam displacer from the first beam displacer side;
A third beam displacer constituted by a birefringent crystal disposed on the opposite side of the first beam displacer from the second beam displacer side;
A third port provided on the opposite side of the third beam displacer from the first beam displacer side;
With
In the second beam displacer, the polarized light beams incident on the first beam displacer from the first port and separated from each other are rotated in polarization directions in the Faraday rotator and the polarization rotator and at least partially overlap each other. Refracted and emitted from the second port;
The polarized light beams incident on the second beam displacer from the second port and separated from each other are rotated in the polarization direction in the polarization rotator and the Faraday rotator, and are further separated from each other in the first beam displacer. An optical circulator characterized by being refracted in the third beam displacer so as to partially overlap and being emitted from the third port. When the polarized lights that are incident on the second beam displacer from the second port and are separated from each other are transmitted through the first beam displacer, the distance between the polarized lights is transmitted through the third beam displacer. The optical circulator according to claim 1, wherein the optical circulator is substantially equal to a distance approaching each other. The optical axis of the first beam displacer and the optical axis of the second beam displacer are parallel,
The optical axis of the third beam displacer and the optical axis of the first beam displacer are symmetric with respect to an intermediate plane between the first beam displacer and the third beam displacer. Or the optical circulator of 2. The thickness of the said 1st beam displacer and the thickness of the said 2nd beam displacer are substantially equal to the thickness of the said 3rd beam displacer, The Claim 1 characterized by the above-mentioned. Optical circulator. The optical circulator according to claim 1, wherein a thickness of the first beam displacer and a thickness of the second beam displacer are substantially equal to each other. The optical circulator according to claim 1, wherein at least one of the first port, the second port, and the third port has a mirror. The mirror is provided adjacent to at least one of the first beam displacer, the second beam displacer, and the third beam displacer;
The optical circulator according to claim 6, wherein the mirror is disposed between at least two polarized light paths that pass through the beam displacer adjacent to the mirror. A fourth beam displacer constituted by a birefringent crystal disposed on the opposite side of the second beam displacer from the first beam displacer side;
A fourth port provided on the opposite side of the fourth beam displacer from the second beam displacer side;
Further comprising
Each polarized light incident on the fourth beam displacer from the fourth port and separated from each other is incident on the second beam displacer and brought close to each other, and the polarization direction is rotated in the Faraday rotator and the polarization rotator, The optical circulator according to any one of claims 1 to 6, wherein the first beam displacer is refracted so as to at least partially overlap each other and is emitted from the first port. The respective polarized light incident on the third beam displacer from the third port and separated from each other is incident on the first beam displacer and brought close to each other, and the polarization direction is rotated in the Faraday rotator and the polarization rotator, 9. The optical circulator according to claim 8, wherein the optical circulators are further separated from each other in the second beam displacer, refracted so as to at least partially overlap each other in the fourth beam displacer, and emitted from the fourth port. When the polarized lights that are incident on the fourth beam displacer from the fourth port and are separated from each other pass through the fourth beam displacer, the distances between the polarized lights are transmitted through the second beam displacer. 10. An optical circulator as claimed in claim 8 or 9, characterized in that it is substantially equal to the sum of the distances close to each other and the distances close to each other when the respective polarized light passes through the first beam displacer. The optical circulator according to any one of claims 8 to 10, wherein an optical axis of the fourth beam displacer is parallel to an optical axis of the third beam displacer. The thickness of the first beam displacer and the thickness of the second beam displacer are substantially equal to the thickness of the fourth beam displacer. Optical circulator. The optical circulator according to any one of claims 8 to 12, wherein the fourth port includes a mirror. The optical circulator according to claim 13, wherein the mirror is provided adjacent to the fourth beam displacer and is disposed between at least two polarized light paths that pass through the fourth beam displacer. An optical circulator according to any one of claims 1 to 7,
A signal light source that emits light incident on the first port of the optical circulator;
A first amplifier that amplifies the light emitted from the second port and injects at least part of the amplified light into the second port;
With
The laser apparatus, wherein the optical circulator emits light incident from the first port from the second port and emits light incident from the second port from the third port. The optical circulator according to any one of claims 8 to 14,
A signal light source that emits light incident on the first port of the optical circulator;
A first amplifier that amplifies light emitted from the second port and reflects at least part of the amplified light to the second port side;
A second amplifier that amplifies the light emitted from the third port and reflects at least a part of the amplified light to the third port side;
With
The optical circulator emits light incident from the first port from the second port, emits light incident from the second port from the third port, and transmits light incident from the third port to the first port. A laser device that emits light from four ports.

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